First modernized GPS satellite Launched

A reader writes "The first GPS 2R-M satellite has launched from Cape Canaveral, Florida on top of a Boeing Delta 2 rocket. The government is now competing with Europe's Galileo system, and has added two additional military channels and one civilian channel, which will increase the accuracy and performance of GPS - as well as increase its resistance to jamming."

Comments

You Will Be Assimilated!

[AKAImBatman]

You know, I was about to ask the rocket scientists hanging around here (hi guys!) about how small new generation comsats were going to be. After all, there has been a tremendous increase in miniturization and technology since the original GPS sats were launched. (e.g. better microprocessors, denser batteries, more efficient solar panels, better propulsion, etc.) If we could get these sats small enough, it might be possible to deploy a GPS system for Mars in one or two launches.

Then I saw the borg cube that assimilated the Willy Wonka Chocolate Factory (Mirror) Excuse me while I pick my jaw up off the floor.

On another note, the picture makes it look like the design hasn't changed much from the original NAVSTAR configuration. I assume that these satellites are merely sharing the same chassis, and have very different internals?

Re:You Will Be Assimilated!

[madaxe42]

You find a way of fitting a Caesium fountain clock in a smaller case.

Re:You Will Be Assimilated!

[Anonymous Coward]

Looks like the just cable-tied 4 racks together, wrapped them in shiny copperfoil and added some barberpoles on top for extra oomph. Off it goes !

Re:You Will Be Assimilated!

[jurt1235]

Depending on the rocket which launches the satellite, there will be a general base for the satellite to be build on. You need to be able to mount the satellite on the rocket. Total reuse of the framedesign will save a significant amount of money, so there will be attempts to reuse the frame, solar panels, and general control systems. This ofcourse if the power signature of the new equipment matches with what the frame can deliver.

One thing is a bit weird though about the first photo. Usually these satellites are assembled in clean rooms with people wearing all kinds of protection against static electricity build up and anti dust covers. So I wonder if the satellite in this picture is just a mockup to make a testfit of the equipment (never trust the drawings).

Re:You Will Be Assimilated!

[lbmouse]

Looks like a device for something out of a Dr. Seuss book. Anywho :), here are some specs.

Re:You Will Be Assimilated!

[pr0nbot]

If we could get these sats small enough, it might be possible to deploy a GPS system for Mars in one or two launches.

OT... something I've been wondering about, with regard to long-range communication with satellites: we know how to do networks now, why aren't we peppering space with small node probes that travel away from Earth (i.e. aren't orbital satellites) but keep in touch with eachother and so can route the data from real science probes back to us from further and further out?

I suppose the number of nodes required would grow at the same order as the volume of a sphere (assuming we want to spray them in all directions) but we actually probably only want to send them out in specific directions.

Re:You Will Be Assimilated!

[AKAImBatman]

OT... something I've been wondering about, with regard to long-range communication with satellites: we know how to do networks now, why aren't we peppering space with small node probes that travel away from Earth

1. Nanoprobes wouldn't have a large enough transceiver dish.
2. We are. Have you heard of the NASA Deep Space Network? Every sat and probe we launch becomes part of NASA's network in space. That's why when they had communications problems with the Mars Rover, they were able to send reset commands from a probe heading elsewhere. As long as they can find a number of sats with the necessary line of sight, NASA can communicate with any probe, anywhere. Even if it's on the other side of the Sun. :-)

(No, I am not privy to the exact locations of anything. So take this with a grain of salt. We have a lot of hardware up there, but space is a big place.)

Re:You Will Be Assimilated!

[dwater]

> So I wonder if the satellite in this picture is just a mockup to make a testfit of the equipment (never trust the drawings).

Perhaps they were worried they'd mix up imperial with metric again. My memory is fading - is this the only notable time?

Re:You Will Be Assimilated!

[Verteiron]

Completely off-topic, but your description (borg cube that assimilated the Willy Wonka Chocolate Factory) cracked me up even before I saw the picture. Having seen the picture, I can say that your description is not only amusing but 100% accurate. Kudos.

Re:You Will Be Assimilated!

[jacksonj04]

Go go gadget mesh networking.

Perhaps what we need to augment this system is a cloud of smaller satellites in orbit armed with short to mid-range tracking so that they can pick out space debris. When something is found which happens to be in the path of something else, it can flag up with mission control so that (if the colliding objects are easily moveable) the offending items can be shunted out of the path temporarily.

Alternatively, satellites which realise something is wrong with themselves can send out a general "I'm screwed" message without needing to wait for LoS to a ground transmitter.

Re:You Will Be Assimilated!

[GileadGreene]

On another note, the picture makes it look like the design hasn't changed much from the original NAVSTAR configuration. I assume that these satellites are merely sharing the same chassis, and have very different internals?

No, they're substantially different designs. Different manufacturers even (Rockwell vs Lockheed). But if you have a spacecraft performing the same mission, odds are it's going to have a similar configuration. The thing that makes them look most similar is the navigation signal antenna array (the "Willy Wonka Chocolate Factory"). Even those are slightly different between the two models. But since they're fundamentally performing the same function, thye look very similar ("form follows function").

Re:You Will Be Assimilated!

[cpu_fusion]

So I wonder if the satellite in this picture is just a mockup to make a testfit of the equipment (never trust the drawings).

Given the military nature of the project, perhaps it is just a "PR model" for secrecy.

Re:You Will Be Assimilated!

[AKAImBatman]

But if you have a spacecraft performing the same mission, odds are it's going to have a similar configuration. The thing that makes them look most similar is the navigation signal antenna array (the "Willy Wonka Chocolate Factory").

Fair enough. I was actually looking at the general shape of the craft, and also was influenced by the story which suggests that the new sats are simply updates of the old ones. On further inspection, it does appear that the two sats are quite a bit different.

Speaking of which, I am wondering what the heck those things on the antenna array are. (Assuming for a moment that they aren't coverings for classified equipment or even just "neat" coverings for publicity photos.) The more squat ones are reminicent of capacitors, but I'm not certain why you'd put them outside of the chassis (i.e. fully exposed) as opposed to inside. The candy-cane style ones look like they're just coverings for antennas. Any ideas?

Re:You Will Be Assimilated!

[speculatrix]

there has been a tremendous increase in miniturization and technology since the original GPS sats

your statement is naive in that it supposes that mil-spec and rad-hardened technology has advanced at the same rate. Once, it was the military who led the way and consumer devices followed; now, it's the other way round, and in fact the military/space people have big problems with obsolescence, especially with the recent EU rules on Reductions Of Hazardous Substances (often known as "lead free", but actually covers other things as well). In some instances, military kit is being forced to use automotive-spec components as replacements, because that's all that's available and at least the devices have a wider temperature range.

so, yes, mil- and space-spec hardware is advancing, but the testing cycle is far longer - think months rather than weeks. when you're spending $M's in launch fees, you've got to get it right!

Re:You Will Be Assimilated!

[josecanuc]

Speaking of which, I am wondering what the heck those things on the antenna array are.

Those *are* the antennas. See the spiral bits on both kinds? That's a conductive strip. It's a helical antenna -- common on satellites. The body that looks like the main bulk is just to give the thin metal something to hold shape.

Re:You Will Be Assimilated!

[AKAImBatman]

Once, it was the military who led the way and consumer devices followed; now, it's the other way round, and in fact the military/space people have big problems with obsolescence

It's still quite advanced equipment, though. Sure, we're not talking about gigahertz processors and multi-gigabyte memory architectures. Instead, we're talking about old Sparcs, Pentiums, and MIPS from days gone by. That's still pretty advanced stuff. And when it comes to the batteries, LiON batteries were actually developed for space use. As for the propulsion, arcjets and ion engines are new technologies that have proven themselves in real satellite usage.

So yes, some stuff is behind the commercial market. But there's still plenty of highly advanced techology that's been rated for space use. :-)

Re:You Will Be Assimilated!

[AKAImBatman]

I didn't realize that, especially since the new sat seems to have other atennas similar to the NAVSTAR. Thanks for the info! Learn something new everyday. :-) (Mods, please mod parent up "informative".)

Re:You Will Be Assimilated!

[bleckywelcky]

You could say the same for the Model T and Ford's latest Mustang. I mean, they both have wheels, right? They both have engines, right? They both have doors, right? Well, they must have not changed much in the design. Hell, what are we paying these morons for?

The overall layout of a GPS antenna is not going to change much, you're always going to have to shoot your signal in a certain direction. However, the efficiency of the components and the effectiveness of the materials has all been re-engineered. As well, I'm sure the bus is being continually improved.

Re:You Will Be Assimilated!

[ChrisA90278]

You've been reading to much science fiction. Yes there are some cases where spacecraft use inderect means of communication through a relay but this is not done ad-hoc using some general purpose capability built into every spacecraft. In every case wherwe relay is used the capabilty is plaanned from the beginning. The idea of selecting some random spacecraft to use as a relay to soe other random spacecraft just can't work. The orbiters currently on mars were design specifically to relay. Closer to Earth TDRSS acts as a relay between low Earth orbit and the ground. Notice (1) that TDRSS is the relay, thaey are NOT sending data between randon spacecraft and (2) the data are passed only between LEO and the ground, not through out the solar system or even to geosync. orbit. http://msp.gsfc.nasa.gov/tdrss/oview.html

Re:You Will Be Assimilated!

[Forbman]

The helical antennae circularly polarize their beams.

Re:You Will Be Assimilated!

[LandKurt]

Have you heard of the NASA Deep Space Network? Every sat and probe we launch becomes part of NASA's network in space. That's why when they had communications problems with the Mars Rover, they were able to send reset commands from a probe heading elsewhere.

Did you even read the Wikipedia article you linked to? The Deep Space Network is an earth based network of large radio dishes that listen to deep space probes. It's not located in deep space. It's almost always easier to talk to a distant probe with a huge dish on earth than to try and use the small dish on another probe.

The closest thing to what you're discussing is NASA's TDRS system. That relays signals from earth orbiting satellites to the ground.

Re:You Will Be Assimilated!

[Xaositecte]

Ehh, not so much. All you really need to make a relay is a few capabilities:

1. Antennas, Preferably ones you can point in the direction you want. Not so hard in space given the (usually) low loss of sending signals through space, and the wide dispersal. Built into every Satellite

2. Transmit\Recieve: Again, assuming you can contact it, and it can contact you, also built into every Satellite.

3. The ability to change transmit\recieve frequencies: Might not have been included on some of the older or more specialized Satellites, but certainly possible these days.

Far from being impossible, assuming a little forethought on NASA's part, it's probably true.

Re:You Will Be Assimilated!

[ciroknight]

If you've seen the discovery channel show about how the construction of the new James Webb Space Telescope, Deep Space 1, or the (most recent one) NEAR probe, you've probably seen that they build a mockup that includes pretty much every part that will ever be on the actual satellite built, but it's built in a non-clean environment so that as many engineers as possible can work on the hardware without the restrictions that the clean room requires. While the mockup can never be flown (dust, fingerprints, all kinds of contaminants just cover these things), and usually isn't built to 100% scale (I think NEAR was built to an 80% scale or something; the show didn't say, but it was definitely a sizeable difference) to save money.

I'll try to dig up some more information later.

Re:You Will Be Assimilated!

[GileadGreene]

What you say is true. In particular, the "hot new" rad-hardened processor is the RAD750, a hardened PowerPC 750. And yet...

• When the GPSIIR-M started the design process the RAD750 was nonexistent - major USAF satellites can take on the order of a decade to design and deploy.
  
• As I've said elsewhere in this thread, electronics are not necessarily that large a contributor to spacecraft mass.
  
• More capable processors may suck down more power, which tends to make other parts of your spacecarft (e.g. the solar arrays) larger.
  
• Li-Ion batteries are still considered relatively unproven in a spacecraft context. They've only been used on a few missions, and the performance and lifetime data we have on them is limited. They are unlikely to be selected for a critical system like GPS at this point.
  
• Li-Ion batteries were speculative "future technology" at the time the IIR-M was being designed. I'm pretty certain they aren't being used in the next-gen GPSIIF satellites. I'd be surprised if they made it into the GPSIII (which isn't due to deploy for another 6-8 years).
  
• Arcjets and other forms of electric propulsion have indeed proved themselves. They are in regular use on GEO comm satellites. However, whether or not EP makes sense for a given mission depends on many things. One key issue is solar array size. Using EP for an orbit transfer makes sense on a GEO comm bird because they have huge solar arrays that won't be used during the transfer - that spare power can be used to run an ion engine. In the case of GPS it's not clear that the arrays are large enough that you wouldn't need to add extra array area just to support an EP transfer - you'd end up saving propellant but making a more massive spacecraft. EP for stationkeeping is another question. But again, there are many tardeoffs involved.
  
• Satellite structures are still mostly made from aerospace-grade aluminum. There's been some work on using composites, but there are issues with outgassing in a vacuum environment, and ease of manufacture.
  
• There's been little in the way of advancements in spacecraft thermal control technology in the past couple of decades.
  
• Spacecraft antenna and RF technology hasn't changed a whole lot. Especially for precision applications like navigation signalling. Where it has changed, it's been used to add more capability rather than lower mass.
  
• Solar array technology has advanced quite a bit. But again, that just provides scope for higher-power applications (greater comm bandwidth, more processing power).
  

None of this means that the IIR-M couldn't be smaller and lighter (I personally believe it could be). But doing so requires careful design and assessment of the tradeoffs involved. Just throwing technology at the problem is not the answer. In fact, it's often the cause of the massive cost and schedule overruns that happne in DoD space programs.

Re:You Will Be Assimilated!

[AKAImBatman]

Excellent post! My hat goes off to you, sir. You've been a most informative source. :-)

So basically what it comes down to, is that it takes so long to get a government bird in the air, that by the time it actually flies it's old tech to the commercial world. Which jibes with what the article states. It's tempting to jump into the "it's pretty sad when you have years to upgrade a sat before it even flies" mode, but the government does make choices that are intended to increase the chance of success. Not chasing new technology as soon as it becomes available is one of those choices. :-)

Re:You Will Be Assimilated!

[saider]

Your proposal for eliminating space junk is to launch _more_ satellites?!?

Also, the volume that needs to be patrolled would need to have so many garbage collectors that the garbage collectors themselves would present a hazard.

The best thing to do is to launch "cleaner" systems and let all the junk eventually fall back to earth.

Re:You Will Be Assimilated!

[GileadGreene]

IMHO it comes down to 3 things (one of which you've already captured):

1. It takes a long time to get a satellite up, and chasing new technology will just make it take longer.
2. It is not a given that a new technology will provide benefits for a given mission. There are interactions between different elements of the design that may mean that a certain technology is not appropriate for the mission in question (the demands of EP on solar arrays being a prime example of this kind of negative interaction).
3. The temptation is always to cram as much capability as possible into the satellite, instead of providing the minimum capability required. This is especially true of government satellites since the requirements are typically ill-defined to begin with (at least in my experience).

These reasons apply to US government space programs. For an alternative approach, you might look at Surrey Satellite Technologies Ltd in the UK. They build and launch things quickly, have a well-defined strategy for integrating new technologies into spacecraft in a low-risk fashion and getting rapid flight-test information on them, make good use of the technologies appropriate to a mission instead of getting wedded to any one tech, and are extremely good at nailing down their requirements and building only what is needed. IMHO they are the best, and most innovative satellite manufacturer in the world today (and no, I don't work for them - although I'd do so in a heartbeat if I ever moved to the UK).

To being things slighly back on-topic, it's probably worth noting that SSTL has the contract to develop a testbed satellite for the Galileo system (the European competitor to GPS).

Re:You Will Be Assimilated!

[Thanatos Starfire]

AT&T said the same thing about packet switching networks when the idea was first proposed to them. But you know, they seem to work quite well. And what would this dispersed mini-node network be but a large network to route traffic through in a similar fashion?

Re:You Will Be Assimilated!

[afidel]

You obviously say that as someone who has never been involved with a piece of communications gear. While software radios and wideband PHI's are starting to be developed today, traditional comm gear has very specially tuned PHI's which can only recieve fairly narrow ranges of signals . These are combined with antenna's which are tuned to the same fairly narrow band of signals to allow ideal amplification and beam focus. Trying to do wide ranging signals with the accuracy needed to communicate over distances measured in AU's just wouldn't work.

Re:You Will Be Assimilated!

[ebief]

IAAEE - I Am An Electronics Engineer and I once wrote a paper on wireless transmission and antennas, and those Willy-Wonka-style antennas on top look like Helix antennas

http://www.af9y.com/helix.htm
http://www.google .no/search?hs=hjx&hl=no&client=firefox-a&rls=org.m ozilla%3Aen-US%3Aofficial_s&q=helix+antenna&btnG=S %C3%B8k&meta=

They are really easy to create, just take som metal wire and wrap it around a toiletpaper center. number of turns and inclination decides spread and gain.

Re:You Will Be Assimilated!

[Detritus]

It's much more difficult than you think. Steerable antennas are complicated, fragile, and prone to failure. Plus, someone has to generate pointing data for the antenna.

i've yet to see a frequency agile transponder. Not that it isn't possible, but all of the ones that I've seen are fixed frequency.

Re:You Will Be Assimilated!

[jacksonj04]

Or if not dedicated satellites, at least those already up there being able to report "I've hit something, dammit!"

Re:You Will Be Assimilated!

[ChrisA90278]

Do you know the formula that relates transmit power, distance, and bandwidth? Of course it is _possable_ to build such a network. My point was that it has not been done Your write "assuming you can contact it, and it can contact you." It depends on the data rates. You can have a 10,000 watt tansmitter on Earth but the power available to a rover on mars may be only a few watts. The links tend to be hugly asymetric. A small Mars rover can send on order of a few hundred bits per second directly to Earth but can send 10X faster to an orbiter that is only a few hundred kilometers overhead. A moveable microwave antenna is not the best setup for switching packets. The antennsa slew at very slow rates and of course when it is pointing at one location it can't pont in others. This is not to say general purposes packet switches can not be built. Look at this www.losangeles.af.mil/SMC/MC/Tsat.htm TSAT will be a switch but it will conect users on the ground not in space. Maybe years from now someone will built a TSAT that looks upward? but I doubt they will add TSAT-like capability to everythingthat is launched.

Re:You Will Be Assimilated!

[Pseudonym]

Caesium is so 20th century. And besides, they actually use up the caesium.

It's fairly well-known that the new GPS satellites use hydrogen MASER clocks.

Re:You Will Be Assimilated!

[Pseudonym]

Whoops, my mistake. It's well known that the new GPS satellites will use hydrogen MASER clocks. I believe this one actually uses a rubidium clock, much like the "newer" old GPS satellites.

At any rate, caesium clocks are definitely history. They're bigger, they use more power, they don't last as long and they're less accurate than rubidium.

Re:You Will Be Assimilated!

[kd5ujz]

You are correct. Helical antennas are set up for circular polarization. they are usefull in ground-->sat-->ground communications, as most satellites are spinning, and a typical yagi/parabolic dish( single axis polorized, horizontal, or vertical) would create a gain doppler effect.

Re:You Will Be Assimilated!

[Detritus]

The last time I checked, cesium was still the overwhelming choice for primary frequency/time standards. Rubidium standards were smaller and cheaper, with poorer performance. Hydrogen masers had better short-term stability than cesium, but poorer long-term stability.

Re:You Will Be Assimilated!

[madaxe42]

Agreed - if they are using hydrogen masers, I presume they don't expect the satellites to have much of a lifetime.

Re:You Will Be Assimilated!

[Anonymous Coward]

It wouldn't be a cesium "fountain" anyway, since those work like this:

(1) laser-trap cool a cloud of 133Cesium atoms below doppler temperature
          (this works by holding only the stillest (that is, coldest) atoms in the light beams; the rest escape because they're too warm (that is, moving energetically)).

(2) drop the cloud of supercooled atoms through a microwave cavity
          (in practice, first you shoot the cesium atoms up, then they fall down)
          (this is done because interacting with microwaves at precisely the right frequency flip the spin of the outermost electron)

(3) measure the ratio of the two hyperfine states or the rate of hyperfine transition
          (you can watch the light as light, or take advantage of the different electrical or magnetic components to do a separation and count)

(4) result of (3) tells us whether our oscillator-driven microwave frequency is too high or too low, and lets us steer the feedback loop to compensate

(5) repeat

(6) ???

(7) Profit!

The difference between the cesium fountain and the cesium beam is in the heat of the cesium atoms and the duration of the interaction with the microwave energy. Colder and longer both reduce measurement error and uncertainty.

Microgravity obviously has several advantages.

Rubidium clocks are cheaper (even in military applications), smaller (good for spacework) and have better short term stability and most importantly, have a longer useful lifetime. There are lots of terrestrial cesium clocks to compare rubidium clocks with in forming a synthesized timescale, which in turn can be used to correct their longer term inaccuracies. H2 masers are becoming lighter and more durable, and don't have as short a lifetime as the other two standards.

Fountains are very experimental, and big -- one fills a large room in Teddington, UK. Trapped ion clocks are even more experimental, though more promising. The principal difficulty is that they need to use much higher radio frequencies than the "mere" 9 GHz microwave range.

Re:You Will Be Assimilated!

[saider]

Heh. They do report problems. The error message is "Lost Carrier".

Re:You Will Be Assimilated!

[Xaositecte]

*Sigh*

You seem to know a little about Satellite communications, but your conclusions are wrong. Power level and data rate only matter inasmuch as what's necessary to get a good Bit Error Rate. On a clear day, beaming up to a geosynchronous satellite, (22,300 Miles up) only about 2 Watts are necessary.

In space, where we don't have the atmosphere to plow through, or local weather conditions, etc. - Beaming to Mars with a smaller atmosphere and almost nonexistent weather, the output power isn't a problem. Yes, even to Mars.

the TSAT system is a large, multi-purpose switch, designed to be a switching station. All it does (or what any comm satellite does for that matter) - is accept information coming into it on one frequency, and broadcast it on another frequency. If it was built with the software to do it, it'd be fairly simple to Jury-rig a switch capable of receiving the signal you send, and repeating it towards the Mars lander (or wherever you wanted to go) on the frequency you want. It's not something you'd want to do on a regular basis on equipment not designed for it (Hence what TSAT and similar systems were created) - but it's possible.

Again, the only barrier to this being done is that little bit of forethought on NASA's part. The technology is there.

Re:You Will Be Assimilated!

[bjheu]

The original Block II and IIA satellites were manufactured by Boeing with multiple subcontractors making components such as the L-Band Transmitters (the circular antenna array). When Lockheed won the contract for IIR They built it around the same chassis that they used for DSCS communication satellites, with the same contractors making many of the subsystems. Ironically the circular antenna array was a design necessity. the IIR-M satellites were originally IIR vehicles that were pulled off the shelf to be modernised in anticipation of Block IIF and III. So no the design hasn't changed much in the last 50 years.

I am also on the launch crew that is putting the new IIR-M vehicle into orbit. :)

Compatibility

[slimey_limey]

Will this improved accuracy come at the cost of compatibility? I already have a GPS reciever, and I don't want to have to buy a new one to make my data more accurate. (Magellan hasn't released new firmware for the SporTrak Basic since 2002, and I'm not holding my breath.)

Re:Compatibility

[AKAImBatman]

The new civilian channel is in addition to the existing channel, so your existing equipment should work. As more of these sats go online, you can expect to see gear that provides access to the second civilian channel. (Source)

What I have to wonder, though, is what will they do with the two new military channels? It seems that all the field soldiers tend to use civilian gear because the military gear is too heavy, unfriendly, ugly, and is in short supply. I suppose it would make the missiles hit their targets better, but it would be nice to know that our entire military can use the equipment.

Re:Compatibility

[geoffspear]

When they turn off the civilian channel, you can bet the military is still going to be using their channels.

Re:Compatibility

[Wyatt Earp]

In each squad I think there is a military grade GPS reciever, since Afghanistan and more so, Iraq, more and more soldiers are carrying thier own GPS hand held which is good enough for field work.

The new military channels will be more for JDAM/Cruise Missiles and other targeting systems.

Re:Compatibility

[Anonymous Coward]

What I have to wonder, though, is what will they do with the two new military channels?

One for them, one for their "allies"?

Re:Compatibility

[Xaositecte]

They can't turn off the civilian channel.

Not without making all those Y2K nightmare fears come true.

Re:Compatibility

[geoffspear]

They "can't"? They have plans to do so in certain situations, whether you think it's a good idea or not.

Re:Compatibility

[Anonymous Coward]

Please elaborate how you came to this conclusion... unless all those Y2K nightmares involved having to go back to a map and compass to go geocaching or having your personal nav system in your car not able to tell you just how lost you really are, I'm not seeing any problems.

Re:Compatibility

[Myself]

Considering that WAAS was announced in 1994 and AOR-W went up in 1997, I don't see much reason for new firmware updates unless there are bugs in the old stuff. There simply hasn't been a lot of change lately.

That being said, WAAS was specifically designed to be usable by existing Navstar receivers, with only a firmware upgrade. Other improvements, like DGPS and LAAS, require specialized hardware and cooperation from a nearby reference station.

A new civilian frequency will require new receivers. The clocks on the new satellites might be a smidge more stable than the old ones, but in order to squeeze more accuracy out of the signal, you'll need a new receiver.

Re:Compatibility

[Firethorn]

Trust me, we can do far more than just shut those channels off.

We can also make them less accurate, spew wrong coordinates, wrong time, etc...

And we can do it by region. Accuracy unaffected in the US, Europe, totally fubar in Afganistan...

That's why Europe was/is looking at putting their own constellation up, because we wouldn't be able to turn it off on them. Only they got upset when we mentioned that we'd jam their signals if we felt it necessary. Then if you consider the expense of putting them up, it doesn't seem like quite as good a deal.

Re:Compatibility

[Xaositecte]

GPS isn't just coordination, it provides incredibly accurate, standard, timing to the world, practically for free.

the US banking system, for one, relies on it almost entirely. Similar to the programming faults that made Y2K such a big problem, removing that timing reference would make nearly every financial institution in the US crash immediately, and for a prolonged period of time.

And that's just the biggest vulnerability...

Re:Compatibility

[Xaositecte]

It'd do more than make boats and planes have a hard time.

Remember all those Cesium clocks broadcasting timing down from the heavens? Wanna know what happens when all the master timing Banks and other institutions who don't see a cost-benefit for having back-up master clocks goes away?

Very bad things.

Re:Compatibility

[Xaositecte]

GPS doesn't even spew coordinates...

Learn how it works, then read the replies I gave the other nonbelievers

Re:Compatibility

[Colonel Blimp]

I have the same GPS, what I really wish is that the GPS signal was strong enough to go a few hundred feet underwater. As a scuba diver, being able to navigate can be difficult, a GPS would make life much easier and safer.

Of course, if the battery goes dead underwater, it would be hard to change them!

Re:Compatibility

[Firethorn]

I was oversimplifying.

A more correct response would be 'Make your receive give the wrong coordinates'.

Spaceballs

[q-the-impaler]

Jammed? Raspberry. There's only one man who would dare give me the raspberry. Lone Starr!

Combining articles

[Anonymous Coward]

Read a couple of days ago about a jamming satellite and now a jam-proof satellite is launched. Are we going to jam the Galileo system? Do the Europeans have to read road signs again?

Jamming, eh?

[gowen]

Because of the risk of Jamming, I forsee an Exodus from old GPS to new, throwing Caution to the wind, putting the alternatives in Crisis. As long as tech can Keep On Moving, I'm going to be in a Mellow Mood, and won't Mix Up, Mix Up these services. After just One Cup Of Coffee (add One Drop of milk, Stir It Up...), I can feel the Positive Vibration this has given me, and Time Will Tell that that Slave Driver of a boss will be Waiting In Vain for my report. Work, Why Should I with So Much Trouble In The World?

Thank You Lord. The score is now One-Love to the DoD.

Re:Jamming, eh?

[SillyNickName4me]

Its all a Rat Race anyway..

Re:Jamming, eh?

[iamlucky13]

I don't get it. My first instinct was to try to find a secret code in the capitalized letters, but that didn't work out. Are you attempting to appeal to the slashdot moderators that appear to be scripts by tossing in keywords? If so you're going about it all wrong. You should start with, "I'm gonna get modded down for this," and include the words space elevator, soviet russia, nucular, linux, and intelligent design. Adding in AJAX, ubuntu, and evolved expanded launch vehicle will bump you up from funny or interesting to insightful.

Re:Jamming, eh?

[blincoln]

My first instinct was to try to find a secret code in the capitalized letters, but that didn't work out.

Jam session.

But yes, that was my first instinct too.

Re:Jamming, eh?

[AScare]

Hint: Marley, Bob ...

  - or is it just a Natural Mystic blowing through the air..?

Jamming by whom?

[moz25]

As I understand, one of the jamming related problems with GPS is not by criminals/terrorists, but by the government when they see the need. It seems more of a political than a technical nature. That's one of the potential benefits of the Galileo system: to have more than one "supplier" of such information.

Re:Jamming by whom?

[LiquidCoooled]

I prefered it when Bob Marley was the only one Jamming.

Re:Jamming by whom?

[Gaima]

http://science.slashdot.org/article.pl?sid=05/08/0 8/1350218&tid=160&tid=103

Re:Jamming by whom?

[AKAImBatman]

As I understand, one of the jamming related problems with GPS is not by criminals/terrorists, but by the government when they see the need.

No, it's more complex than that. Yes, the government can fine tune the results to cause problems for enemies, and even turn off the unencrypted civilian bands if they so choose. However, real methods exist for sending confusing signals that will effectively jam a GPS signal. This jamming can force so called "smart bombs" to rely on internal guidance instead of GPS. The result (hopefully) is that the less precise guidance would cause the bomb or missile to miss the target.

In practical terms, it seems a bit harder than that to prevent US munitions from reaching their targets. Our guidance computers were well developed prior to the general use of GPS coordinates, and we have the capability to manually deliver ordinance wherever it may be needed. So in the end, this is about keeping the efficiency of our weapons in good order so that we have to risk fewer lives in missed targets and strafing runs.

Re:Jamming by whom?

[Dun Malg]

However, real methods exist for sending confusing signals that will effectively jam a GPS signal. This jamming can force so called "smart bombs" to rely on internal guidance instead of GPS. The result (hopefully) is that the less precise guidance would cause the bomb or missile to miss the target.

Problem with active GPS jamming is that it's a "damned if you do, damned if you don't" situation. Any sort of active jamming on the battle field is a huge beacon on the battlefield screaming BLOW ME UP! It then becomes a question of whether or not to turn on the jammer at all, as at most it'll be good for slightly de-accurizing (if that's not a word, it ought to be) one bombing run before being obliterated. If they were cheap enough, maybe, but even still...

Re:Jamming by whom?

[w42w42]

I remember watching a press conference with a military general at the opening of the last gulf war. The press was all lathered up about reports that Iraq was jamming GPS signals - it was assumed the Russians had given them the equipment - and the general commented that whoever was running that equipment had the worst job with the shortest life expectancy in the world at that time. Like you alluded to, any military equipment that relies on an outgoing radio signal instantly becomes a big bright target.

Re:Jamming by whom?

[mcd7756]

They become suicide bombees instead of suicide bombers.

Re:Jamming by whom?

[soft_guy]

Can they not use multiple stations to make it appear the signal is coming from a place where it is not?

Re:Jamming by whom?

[spankus]

Actually, because of the incredibly low power GPS transmits at...it is possible to design a GPS jammer that broadcasts BELOW the ambient noise floor that will still impact GPS receivers.

Sparkus

Re:Jamming by whom?

[turbotalon]

Smart bombs themselves do not directly rely on GPS. The aircraft they are released from gets a solid fix before dropping the bomb, then the bomb relys on intertial guidance. I would think it would be pretty obvious to the pilot/bomber that his GPS was being jammed and his position was freaking out. Also, once the bomb is dropped, it will be accurate even if the whole GPS system went down.

Re:Jamming by whom?

[bluGill]

True, but there is little point in battle field jamming of GPS. Anyone with a set of eyes (last I checked military refuse the blind) can navigate to any ground target with just a map, which cannot be jammed. (A compass helps, as do stars and the sun, all of which are hard to jam. Still dead reckoning just by knowing your original direction is often to get there) Targets are visible from miles away. A city doesn't move, and can often be seen 30 miles away or more. Targets that do move need those eyes anyway because the GPS can at best take you to where it was.

The purpose of jamming GPS is for missiles. If the Soviet Union launched a ICBM at a US city, using GPS, jamming the signal is enough to make the missile most likely to hit farmland outside the city. Bad for the farmer, but much less deaths than hitting the city (or whatever the target is). Of course the Soviet Union is long gone, and nobody else has ICBMs, so there is no point in jamming GPS anymore - at least not for anyone with the ability to pull it off. In fact the US wants the bad guys to think GPS is not jammable (and it is hard to do), in hopes that they will cheat and use GPS for misstel guidance - then after the launch they turn on selective ability, and the misstel lands in a relatively harmless area.

Re:Jamming by whom?

[nsayer]

any military equipment that relies on an outgoing radio signal instantly becomes a big bright target.

Yup.

And I rather suspect that HARMs are not limited to air defense radar systems...

Re:Jamming by whom?

[Anonymous Coward]

Yeah, I was looking for someone else saying that. As soon as you broadcast that signal, Sam Fisher is gonna show up, grab you from behind, and hold a knife to your throat until you tell him the four-digit password to the computer controlling the transmissions.

Hey, that should be a mission in the next Splinter Cell. Instead of shutting it down, readjust it so it actually augments the real GPS signal.

...Pardon, been playing a bit too much Chaos Theory lately. :P

Re:Jamming by whom?

[NatasRevol]

Unless that target is another satellite. Say a second generation of GPS that is, strangely, heavier than the first generation.

There aren't many countries in the world that can quickly and accurately take out a satellie that is beaming a jamming signal.

Re:Jamming by whom?

[__aaijsn7246]

Phrack magazine awhile ago had an article about building a Low Cost and Portable GPS Jammer.

Re:Jamming by whom?

[Dun Malg]

Can they not use multiple stations to make it appear the signal is coming from a place where it is not?

No, all that would do is present multiple individual targets. Modern direction finding equipment uses such advanced digital processing that it can separately identify two transmitters right next to each other based on subtle differences between them caused by things like inherent manufacturing variations in the transmitters' modulation circuitry.

Re:Jamming by whom?

[Anonymous Coward]

True, but there is little point in battle field jamming of GPS

Not so.. GPS is used to give coordinates for smart bombs. These GPS coordinates can be provided by ground based troops based on a suitably enhanced binoculars that will determine absolute position of an object in sight - thereby allowing troops on the ground to call in a smart bomb targetted to anything they can see.

Re:Jamming by whom?

[Mr. Underbridge]

Well, I'm guessing that the guy who sets them up doesn't hang out to watch them work. I'm also guessing they get activated remotely, because I wouldn't want to be the guy driving away from a jammer after it goes live, either.

Re:Jamming by whom?

[Anonymous Coward]

Why would the US military need to jam their own GPS signal? They're more then capable of shutting out everyone else out from reading the information through some sort of encryption if I recall correctly.

Re:Jamming by whom?

[Firethorn]

A few other countries have ICBMs. China, England, Iran's on the edge.

They just down have enough to effectivly carpet bomb the USA like the USSR did.

Re:Jamming by whom?

[Anonymous Coward]

I hate to nit-pick, but thought you might be interested:
nobody else has ICBMs

http://en.wikipedia.org/wiki/Icbm

Re:Jamming by whom?

[Dun Malg]

Actually, because of the incredibly low power GPS transmits at...it is possible to design a GPS jammer that broadcasts BELOW the ambient noise floor that will still impact GPS receivers.

True, but when you jam GPS you usually have to overcome the unavoidable fact that your signal is coming from the ground. The GPS antenna on the guidance tailkit on these bombs is at the very rear, which places the entire body of the bomb between it and any jammer located near the target. This increases the power requirement significantly. Besides, the fact that the selective availability signal is encrypted means that the best they can hope to do is disrupt the signal, as spoofing in any meaningful way requires valid encryption keys. As soon as the guidance system finds itself being jammed it switches over to inertial guidance and, unless you got some sort of gravity generator, there's no jamming that.

Re:Jamming by whom?

[Dun Malg]

True, but there is little point in battle field jamming of GPS

Not so.. GPS is used to give coordinates for smart bombs. These GPS coordinates can be provided by ground based troops based on a suitably enhanced binoculars that will determine absolute position of an object in sight - thereby allowing troops on the ground to call in a smart bomb targetted to anything they can see.

Yep. But of course that's why they still teach map n' compass navigation. We were trained to call in artillery strikes in the pre-GPS days with easily sub-20m accuracy. A decent map and a laser rangefinder, I could call out sub-10m target positions, no problem.

Re:Jamming by whom?

[Shakrai]

And I rather suspect that HARMs are not limited to air defense radar systems...

I suggest you remember that the next time you are trying to mooch off my open Access Point ;)

Re:Jamming by whom?

[DevoPhl]

As I understand, one of the jamming related problems with GPS is not by criminals/terrorists, but by the government when they see the need. It seems more of a political than a technical nature. That's one of the potential benefits of the Galileo system: to have more than one "supplier" of such information.

This was the reason the Europeans put up their own GPS in the first place. The US always contended the current GPS system was for military use only but provided the signals, in degraded form, for private use. The bottom line was that at any time, the US could cut off all private use of the GPS signal if it felt there was a security threat to the US.

The Clinton administration removed the degraded restriction in the late 90s but the military cutoff still remained. As everything from marine and aviation navigation to commercial uses such as truck and train locating became dependent on GPS in the 90s it was clear that ending use of GPS was going to wreak havoc on many systems.

After 9/11, the Europeans realized that depending on a US system was too risky and decided to circumvent US GPS systems and put up their own. The US threatened to jam the European GPS signal. I haven't heard whether this has been resolved or not.

But what I've heard recently is that the European system has much greater accuracy than the now antiquated US system. This probably forced the military to upgrade their network, hence the 2R-M series. We'll see how this battle pans out.

Re:Jamming by whom?

[Anonymous Coward]

Make a few dozen cheap, battery-powered jammer boxes, launch them via ballon.

Re:Jamming by whom?

[Beatlebum]

So you thesis that jamming GPS can cause smart bombs to be less precise, but since "guidance computers" are "well developed" it really wouldn't make much difference.

Hmmm, ok.

Jamming GPS would hurt assets on the ground more than it would prevent smart bombs from reaching their targets. The reason is without GPS troops have to rely on several methods to calculate position, each of them has a relatively large error, not to mention human factors. For example ded (deduced) reckoning relies on identification of known features and comparison with a map; obviously this ain't much use in the desert.

Smart bombs such as the Boeing JDAM tailkit, which attaches to a 500/1000/2000lb dumb bomb, rely on GPS and inertial guidance. The aircraft dropping the bomb communicates its position to the bomb at time of drop, without GPS the bomb then uses its inertial guidance system to calculate relative position to the drop point and therefore its absolute position. Inertial guidance works by using gyroscopes to fix the position of a plane so that an orthogonal line intersects some known point in space, the gyroscopes keep the plane stable no matter how it is accelerated in space, the distance the plane moves to stay in position is measured by the guidance computer to calulate relative position. Modern initertial guidance systems are extremely accurate, accurate enough to position Ohio Class Ballastic Missile Subs that would have to surface to use GPS.

Re:Jamming by whom?

[Detritus]

JDAMs have GPS receivers.

Re:Jamming by whom?

[techno-vampire]

Over thirty years ago I was working on a missile system that would automatically home on any jammer if it lost its signal. I'm sure our smart bombs today are built to do exactly the same thing, and if they're not, they easily could be. As you say, trying to jam GPS is a good way to get your position bombed.

Home Made Cruise Missiles !!!

[Anonymous Coward]

The downisde, of course, is that "Crimson Jihad" or whoever can now make cheap cruise missiles to shoot at us.

Re:Home Made Cruise Missiles !!!

[ghukov]

like this one? The public channels are off to a certain degree so they wouldn't be able to accurately target what they want to hit. But I imagine if the payload is large enough, the "splash damage" could wreak some havoc

Signal jamming==profit

[jurt1235]

Step plan to GPS signal jamming profit:
1. Launch GPS satellites and sell lots of GPS devices
2. Launch jamming satellite (last week news)
3. Launch new GPS satellite system which is less prone to jamming
4. Sell new receivers => profit!

Re:Signal jamming==profit

[cashman73]

In Soviet Russia, GPS owns you!

Or, in occupied Iraq, GPS owns you! :-)

Re:Signal jamming==profit

[Anonymous Coward]

correction:

1. Launch GPS satellites and sell lots of GPS devices
2. Launch jamming satellite (last week news)
3. Launch new GPS satellite system which is less prone to jamming
4. Sell new receivers
5. repeat 2-4 => profit!

Look everyone! Somone who didn't RTFA!

[tgd]

;-)

Seriously, they talk about that in the article. Its a little bit of modernized hardware in essentially the identical satellite.

Re:Look everyone! Somone who didn't RTFA!

[AKAImBatman]

Yeah, I did read it. The part that stuck out to me was that the new sats were about 60 pounds heavier than the old ones. Now I understand that they couldn't have gotten all the new features in for only 60 pounds without modern technology. Still, I can't help but think that it could have been a lot smaller than that.

Then again, I'd like to see a day when we can create useful PongSats, for this stuff but I supposed that won't be happening anytime soon. (Especially not when you need a large tranceiver!)

Re:Look everyone! Somone who didn't RTFA!

[cerberus4696]

You have to remember that they're overengineering these things by terrestrial standards, because the satellites have to withstand some fairly harsh conditions while in orbit (such as radiation, EM storms from solar flares, etc). I imagine they're also hardened to some degree against human-generated interference, given all the worrying the Air Force has been doing lately about space warfare. Given all that, I'm not surprised that they seem excessivly bulky by the standards of present technology.

Re:Look everyone! Somone who didn't RTFA!

[GileadGreene]

The thing is making a satellite slightly lighter doesn't buy you much. You need a substantial drop in mass in order to get down to a cheaper launch vehicle. So given that you're already constrained to launch on a particular LV, why not pack in as much capability as possible? The Air Force in particular has a habot of keeping upgraded satellite designs at the same (or similar) mass as their predecessors, but adding lots of extra functionality.

The other thing to keep in mind is that there are many things that contribute to the total spacecraft mass in addition to the electronics. Not all of them have undergone the same kind of Moore's law reductions in mass (or improvements in capability) that electronics have.

Re:Look everyone! Somone who didn't RTFA!

[Anonymous Coward]

How to build a satellite:
1. Figure out how much you want it to weigh.
2. Use the smallest, lightest and most expensive components available to keep volume and mass down.
3. Use the remaining weight on rocket fuel to keep the satellite in orbit.
4. ???
5. Profit

Re:Look everyone! Somone who didn't RTFA!

[Anonymous Coward]

Silly habot, trix are for kids!

Its about time

[dj245]

The sattelites up there are fairly old. Some of the newer ones were launched only a couple years ago, but some have been up there since the early 90's or before. We've had the math equations and the computing technology to be able to put up satelites with around 1m accuracy and better signal strength for a couple years now. Forget about the better jamproofing; with the newer eqipment you can sum the error of your integrals with newer algorithms and faster and determine position that much better less error-prone initial conditions.

Re:Its about time

[Anonymous Coward]

Holy crap does that last sentence hurt the baby Jesus.

Re:Its about time

[spankus]

Do you upgrade your computer every time a new processor comes out????

Same reasoning (sorta) applies to GPS. Why throw away a $100,000,000 satellite when it hasn't died yet?

The newer satellites do have some expanded capabilities, but don't plan on seeing those operationally for 5 to 8 years. (It's a long story of governmental mismanagment and strife)

Re:Its about time

[Doctor Memory]

Actually, the satellites themselves have no "accuracy" to speak of. It's entirely up to the receiver. With a good carrier-phase differential receiver, you can get accuracies of ~1cm from the existing GPS satellites.

Re:Its about time

[gunnk]

Do you upgrade your computer every time a new processor comes out????

Bad analogy, there, you're posting on Slashdot after all...

Re:Its about time

[dj245]

They do, to a point. Keeping accurate time is critical to knowing exactly where your sattelite is. The sattelite must keep the time, not the receiver. Ground stations upload time updates to the sattelites periodically, but more accurate clocks onboard sattelites will help keep them up to date over time.

In addition, the more frequencies a sattelite broadcasts on, the more accurate the doppler shift can be calculated and corrected for. If it only broadcasts on two, only a crude correction can be applied. Three can calculate a better doppler correction, etc.

Re:Its about time

[Doctor Memory]

The comment I was replying to inferred the satellites had some sort of spatial accuracy, so that's the point I was addressing. But yes, they have extreme temporal accuracy.

How do you compete with vaporware (Galileo)?

[Anonymous Coward]

" The government is now competing with Europe's Galileo system "

Lets see :
        Galileo has not launched yet.
        Galileo will not be free.
        The 2R-M was planning before Galileo was anounced.
        Galileo operational capibility is not planned until 2008.

I'm failing to see the link to the vaporware...

Re:How do you compete with vaporware (Galileo)?

[Anonymous Coward]

this is once again the proof that we need competition.

if GPS doesn't want to be out of business, they need to update NOW.

Re:How do you compete with vaporware (Galileo)?

[torpor]

where does it say none of those things will happen? its possible to compete, and yet your competitor isn't in the race. YET.

Re:How do you compete with vaporware (Galileo)?

[Anonymous Coward]

Having worked on the Galileo internal operating software, i can say operation in 2008 is somewhat optimistic.

Re:How do you compete with vaporware (Galileo)?

[Anonymous Coward]

Hey, it's a European co-operation; we'll be lucky if we see it before 3008. It'll take 50 years just to translate the manual into all 15 languages.

Re:How do you compete with vaporware (Galileo)?

[aperezbios]

Wrong. Do your homework before you make idiotic claims such as "Galileo will not be fre"

From the Galileo Wikipedia Article: (http://en.wikipedia.org/wiki/GALILEO_positioning_ system)

"An encrypted higher bandwidth Commercial Service with improved accuracy will be available at an extra cost, while the base Open Service will be freely available to anyone with Galileo compatible receiver."

Re:How do you compete with vaporware (Galileo)?

[offlerthecrocgod]

Actually it's meant to begin user deployment in 2008. It won't be available to anyone before then. They are not payload testing for fun.

which #

[allelopath]

Is there a way to know which # (1..24) this one is replacing?
Just curious...it would be fun to know when i turn on my GPS receiver.

Re:which #

[Ossifer]

From TFA:

GPS 2R-M1 will assume the Plane C, Slot 4 position, taking over for the GPS 2A-20 craft launched in May 1993.

Re:which #

[Feyr]

from the article:

GPS 2R-M1 will assume the Plane C, Slot 4 position, taking over for the GPS 2A-20 craft launched in May 1993.

Re:which #

[Toaste]

From the article: "GPS 2R-M1 will assume the Plane C, Slot 4 position, taking over for the GPS 2A-20 craft launched in May 1993."

From the designation of the old satellite, I presume that this position is number 20 on GPS receiving equipment. Just a guess.

By the way, does anybody know how they plan to move the old one out of the way? According to info found here the origional was a 3-axis stabilized NAVSTAR, but I doubt it will be able to move significantly with only its thrusters.

Another interesting point: the page lists the design life of this series at 7.5 years. Which means this satellite was replaced a mere 4 years, 10 months, and 13 days beyond its expected service life.

Re:which #

[allelopath]

>> I presume that this position is number 20 on GPS receiving equipment. Just a guess. i didn't know for certain, either, which is why i asked

Re:which #

[Hrdina]

Actually, it will appear as PRN (pseudo-random noise) #17 on receiving equipment. That PRN is currently unused. The current vehicle in slot C4 is PRN07, and it will keep that PRN assignment until it is decommissioned by the USAF.

Too Little Too Late

[qwp]

I would have been able to post first post,
had i known about this great achievement. The problem is
I was suck in my car cause I took a wrong turn due to my
dam'ed gps navigator. Maybe they haven't turned it on yet..

Re:Too Little Too Late

[Anonymous Coward]

It takes more than good GPS to get first post. The first thing you should do is quit your job, because employment will seriously hamper your ability to get first post. Then, of course, you will probably have to live in your mother's basement, since you don't have any money, but no one ever said being a first post whore was easy...

--
__________

|rip/\/\aster /\/\onkey

Specs?

[adminispheroid]

Anybody know what's on the new civilian channel? e.g. is it the same kinda stuff as the two existing channels, on a new carrier? Or is it a new code?

Re:Specs?

[Anonymous Coward]

The new civilian code is probably a longer signal that repeats less often. This gives better accuracy but takes longer to determine position when first switched on. Using the lower accuracy signal would allow for a rapid first estimate of postion while the GPS would become more accurate once the position using the new signal was calculated. The military GPS systems use the civilian signal to estimate their position more quickly.

Re:Specs?

[OnlineAlias]

I know the new one has Howard Stern...oh wait..

Re:Specs?

[Forbman]

Anybody know what's on the new civilian channel?

New episodes of "Lost".

Re:Specs?

[stienman]

Anybody know what's on the new civilian channel? e.g. is it the same kinda stuff as the two existing channels, on a new carrier? Or is it a new code?

According to one of the press conference questions:

"We are not going to confirm the content of the new channel at this time. We can state, however, that due to recent FCC regulations affecting our public broadcast, we will not be including Howard Stern for the initial lineup."

I hope this helps.

-Adam

First Modernized?

[Anonymous Coward]

I know it's nitpicking but.. redundant a little? Isn't this a true statement any time we release a new version of anything that isn't an exact copy of what the previous version was?

Besides... the U.S. has their jammer satellite

[Animaether]

U.S. Deploys Orbital Communications Jammer

so even if Galileo were up, etc. who cares ? the U.S. can just jam them all ;)

or, heck, if need be - shoot them with a rocket. Be a bit debris-rich in result, though, which isn't very desirable

Re:Besides... the U.S. has their jammer satellite

[Sanity]

Come on, almost any industrialised nation, including many if not all countries in the EU, Japan, and others, could shoot the GPS system out of the sky within the first few hours of any war. These navigation systems only ever exist with the consent of other powerful nations.

Re:Besides... the U.S. has their jammer satellite

[ckaminski]

Actually, I'd wager that Russia and perhaps one or two of the other ex-Soviet Republics have the technology to hit a target at 10,000km. Whether or not they'd have 20-30 missiles capable of doing it is something entirely different, when you'd probably want to be lobbing nuclear weapons at your enemy instead.

Re:Besides... the U.S. has their jammer satellite

[mforbes]

Sure, but why bother trying to hit the satellites at all when simply lobbing a few nukes into the ionosphere does the job just as well? (Granted, you destroy your own communications abilities at the same time, but hey, it's not like they'll outlast an all-out nuclear war anyway...)

Re:Besides... the U.S. has their jammer satellite

[Anonymous Coward]

I'd not be surprised if the Russians couldn't fry the electronics in a GPS satellite (or any other) with a land-based particle beam weapon. No need for missiles.

Re:Besides... the U.S. has their jammer satellite

[Anonymous Coward]

Well an F15 has killed two stats in that range so far (out of two attempts). We don't know about others.

Re:Besides... the U.S. has their jammer satellite

[Anonymous Coward]

Do you have a link to these missles that you speak of? I know the US has anti-sat missiles, as I'm sure Russia has, but I don't think anyone else has the capability to shoot 30+ satellites.

Re:Besides... the U.S. has their jammer satellite

[dougmc]

could shoot the GPS system out of the sky within the first few hours of any war

I suspect that we could fry satellites from ground if we really wanted to. Take a large dish, point it directly at the satellite, and pump a gigawatt of microwave RF noise into it. And it would be very precise ...

Satellites are indeed hardened against radiation of all sorts, and can even reboot themselves if some radiation penetrates the CPU and causes something unexpected, but at some point enough power is going to cause damage.

And of course, with less power you could overload it's receivers, especially if you can transmit on exactly the frequency they're listening to. And it would be hard to track -- it wasn't that long ago that somebody was jamming a specific satellite for quite some time. I think it was determined that the signal was coming from Cuba, but they never did narrow it down further ...

Re:Besides... the U.S. has their jammer satellite

[Anonymous Coward]

Yes we do know, the program was cancelled in 1988...

http://www.astronautix.com/lvs/asat.htm

Unless the new ABM system we are deploying in alaska has a yet untested asat capability we lack the capability. Note it is not designed to lob the interceptor to the navstar altitude.

Link to the abandoned soviet system (from the 70's)
http://www.astronautix.com/lvs/asat.htm

A better link on the history.
http://www.astronautix.com/craftfam/starwars.htm

Note the us ASAT system had a max theorized altitude of 620 miles, navstars (gps) orbit at 12,000 miles. It comes up a little short. Navstar is not a low orbit satelite, and hitting 28 of them at once will require 28 large launches over the course of a day that will raise many eyebrows (dam celestral mechanics). If you have that many large missiles just lob the damm nukes.

Re:Besides... the U.S. has their jammer satellite

[Anonymous Coward]

Huh what? Link please?

Re: It's a retrofit!

[belchingjester]

From TFA, the 2R series were already built, but the opportunity was taken to retrofit the last 8 with upgraded capabilities. The last place I would retrofit would be the chassis...

New GIS+RS website! slashgisrs.org

[Lord Satri]

Humm, I'll start stealing slashdot's content for our new slashsite! :-)

Want to discuss GPS stuff or anything related to geospatial like GIS and Remote Sensing, visit the brand-new http://slashgisrs.org/ website. Ad-free and non-for-profit.

It has just launched (last friday afternoon), so plenty of low uid still available ;-)

competing?

[MooseTick]

"The government is now competing with Europe's Galileo system"

It is also competing with the gps system I am building in my garage and will launch from my backyard in 2015.

The European system hasn't left the ground yet. Let's not call it competing until it is functioning. Also, how are they competing? Does the US system make money?

Re:competing?

[pasword ***]

Does the US system make money?
Aren't the largest suppliers of gps products American companies? They pay taxes...

Re:competing?

[MooseTick]

I'm sure the US is getting a great return on investment! That's probably why they build roads. That helps sell cars that they can tax. NASA probably invented velcro so Nike could use it for kids shoes that could be taxed.

btw slashgisrs.org is SlashCSS-based

[Lord Satri]

Oh, forgot to mention, http://slashgisrs.org/ is based on SlashCSS, probably the first brand new slashsite using SlashCSS :-)

SlashCSS/slashdot announcement:
http://slashdot.org/article.pl?sid=05/09/22/132420 7

I see jamming in action regularly

[RebornData]

I use a laptop-integrated GPS in my car, and I drive by the Pentagon regularly for work. The GPS goes nuts on certain roads that pass near the building... the "position" of the vehicle jumps all over the place. Same thing happens near the capitol building. No suprise of course...

-R

Re:I see jamming in action regularly

[SlayerofGods]

How effective would that jamming really be.... since anyone smart enough to build a cruise missile that could use GPS for guidance would be equally intelligent enough to build a cruise missile to simply home in on the jamming single it's self. Or even with out that could simply free fly the last little distance around the jammer and still hit extremely close to the target.
And if your talking about a suicide attacker in a plane; how exactly is losing your GPS location when your within visual range of your target going to stop you.....
What exactly are they trying to protect against?

Re:I see jamming in action regularly

[Kjella]

How effective would that jamming really be.... since anyone smart enough to build a cruise missile that could use GPS for guidance would be equally intelligent enough to build a cruise missile to simply home in on the jamming single it's self. Or even with out that could simply free fly the last little distance around the jammer and still hit extremely close to the target.

1) He might not know it is there
2) The jamming dish (or array of jammers) is presumably far away from any critical installation. If the military managed to radio mark their own targets, I'd classify that as gross incompetence. (also, that'd be "the jamming signal itself")
3) "Simply"? Yes, you could make a system that would try to determine a "last known good position/direction", calculate direction and distance to target and fly it in blind, but it'd be a rather major modification. A much more likely scenarion is that someone gets their hands on a GPS-guided missile (american, russian, whatever), program it up with coordinates and launch it only to fail miserably.
4) Who's to say the system can't actually deflect missiles? Instead of going wild (that's just the default state), an incoming missile detected on radar can be "redirected" to a designated detonation area, simply by making it believe it is hitting the target.

Kjella

Re:I see jamming in action regularly

[Rich0]

I wonder if GPS signals are authenitcated in any way? If not, the Iraquis could do the same thing (redirecting bombs). Of course, US bombs would use the encrypted military channel, so that would prevent Iraqi spoofing (although the US could spoof those bombs if they desired).

Re:I see jamming in action regularly

[Anonymous Coward]

If you're driving by the Pentagon or the Capitol building, do you really need GPS? You should be able to figure out where you are by just looking out the window.

Re:I see jamming in action regularly

[afidel]

In the case of the Pentagon I assume it is to keep someone from hitting the nuclear generator with a tunneling warhead. Of course no one with the technology to make a tunneling warhead is going to use it without also carpet bombing with MIRV nuclear warheads so protecting the generator is a little moot.

Re:I see jamming in action regularly

[SlayerofGods]

It would be pretty hard to fool the missile into flying into a designated area given the way GPS works (IE it's not telling the missile where it is, rather the missile is figuring out where it is from microsecond timing which would be hard to fake in an area as small as a few blocks around a building)

But anyway, it wouldn't be a major modification at all. Just turn off the guidance for the last few seconds and assume your still on course. Now as long as there's not something freakish like 100MPH winds in the area the missile should still fall directly on it's target give or take a few feet.

Re:I see jamming in action regularly

[Anonymous Coward]

The nav in my toyota keeps me solid on the road, never jumps, when I drive by the pentagon and whenever I'm in DC.

You have "lock to road" mode on. That's a sucky mode for wimps that tries to overcome a poor receiver and a poor antenna.

Since I'm off-road a lot, that mode is stupid for me.

Re:I see jamming in action regularly

[Dun Malg]

How effective would that jamming really be.... since anyone smart enough to build a cruise missile that could use GPS for guidance would be equally intelligent enough to build a cruise missile to simply home in on the jamming single it's self.

THis sounds like a completely different situation than jamming. Jamming would just make the GPS unit lose signal lock. If the GPS is showing the location jumping all over the place, US government buildings are protected by some sort of actual false signal. The false signal isn't necessarily coming from the ground either, as the GPS system is controlled by the US government. It's very likely that the non-encrypted channels have heavy errors introduced around government buildings.

Re:I see jamming in action regularly

[Anonymous Coward]

The false signal isn't necessarily coming from the ground either, as the GPS system is controlled by the US government. It's very likely that the non-encrypted channels have heavy errors introduced around government buildings.

The satellites don't know where you are. And even if they did, they broadcast the same information (I think it's basically time signals and orbital parameter updates) to everyone receiving that channel.

If this effect is really happening, it is more likely due to the receiver or else the mapping software.

Re:I see jamming in action regularly

[Dun Malg]

The satellites don't know where you are.

True. But they know where the US Capitol and the Pentagon are.

And even if they did, they broadcast the same information

Not necessarily. It's already well known that they can selectively turn off the signal in arbitrary geographic areas. It's hardly a leap at all to selectively introduce errors around particular spots.

If this effect is really happening, it is more likely due to the receiver or else the mapping software.

Indeed, that's the most likely cause. I'm just saying that if it is being spoofed, it's more likely being done at the source rather than the more unreliable method of putting an antenna on the roof.

Re:I see jamming in action regularly

[mykdavies]

I'm just saying that if it is being spoofed, it's more likely being done at the source rather than the more unreliable method of putting an antenna on the roof.

I don't think you understand how GPS works. Essentially every satellite broadcasts a highly accurate time signal. As these satellites are all at different distances from an observer, these signals arrive at the observer at slightly different times. The receiver has an internal table of positions of the satellites, and uses this table and the time-delays to triangulate its own position.

So, as the grandparent said, the system doesn't 'know' where you are, and so it can't send you different information depending on where you are.

Re:I see jamming in action regularly

[Dun Malg]

I don't think you understand how GPS works. Essentially every satellite broadcasts a highly accurate time signal. As these satellites are all at different distances from an observer, these signals arrive at the observer at slightly different times. The receiver has an internal table of positions of the satellites, and uses this table and the time-delays to triangulate its own position.

I know precisely how the system works. You're failing to understand the point I'm making. So, as the grandparent said, the system doesn't 'know' where you are, and so it can't send you different information depending on where you are.

GPS satellites do not use omnidirectional antennas, simply broadcasting their signal. They have the capability of "turning off" the unencrypted civil frequencies for arbitrarily designated geographic areas, i.e. they could instruct the satellites to render all civilian GPS units useless in Afghanistan during an invasion. This is not speculation, this is part of the design of the GPS system. I said it before, and I repeat it here again:

Given that they can "black out" arbitrarily defined geographic areas, preventing civilian GPS units from functioning within those areas (this point is not debateable-- it's a fact of the GPS system design), it's not too great a leap to say that they might also be able to transmit badly error-mangled signals to arbitrarily defined geographic areas, even areas as small as the near vicinity of the US Capitol and the Pentagon. This doesn't require the GPS satellites to "know where you are", and I never said it did. It only requires the GPS satellites to know where the Capitol and Pentagon are.

Re:I see jamming in action regularly

[Zelea]

It's of no use that the GPS satellites know where the Capitol and Pentagon are. These satellites are just beacons and the only way you can adjust their accuracy is based on their own position. It's true you can alter precision over Afganistan but you can't select small areas. It all has to do with the satellite visibility from the ground. It takes hundreds of miles on the ground to lose visibility.

The jumping around sensitive areas is done by ground jamming; it has nothing to do with the GPS satellites. The jammers on the ground have only enough power to overcome the satellite signal in the area of interest. All what these jammers do is sync with an incoming GPS satellite transmision and insert advanced/delayed position pulses.

Re:I see jamming in action regularly

[Dun Malg]

It's of no use that the GPS satellites know where the Capitol and Pentagon are. These satellites are just beacons and the only way you can adjust their accuracy is based on their own position. It's true you can alter precision over Afganistan but you can't select small areas. It all has to do with the satellite visibility from the ground. It takes hundreds of miles on the ground to lose visibility.

Appparently it is you who does not completely understand how the GPS system works. Turning off GPS availability for a specific area involves more than just "switching off" the satellite when it's "overhead". It's simple orbital mechanics. Their orbital period is about 11hrs 58mins, and they remain visible from any given terrestrial point for 6-7 hours. Therefore, unless you're shutting off GPS service for an area comprising approximately half the earth's surface centered on the spot you want to black out (and that is clearly not the case), obviously there is some degree of directional selectivity from individual satellites. They're not "just beacons" in the sense that any receiver with line of sight gets the same signal. They can and do use multiple antennas and interferometry tricks to affect availability. The only questions that then remain are how small an area can they black out, and can they perhaps choose to instead introduce a much worse version of the old Selective Availability random error factor to that area.

The jumping around sensitive areas is done by ground jamming; it has nothing to do with the GPS satellites. The jammers on the ground have only enough power to overcome the satellite signal in the area of interest. All what these jammers do is sync with an incoming GPS satellite transmision and insert advanced/delayed position pulses.

More than likely this is the case. I was merely wondering aloud whether this is necessarily the case.

Re:I see jamming in action regularly

[Zelea]

Turning off GPS availability for a specific area involves more than just "switching off" the satellite when it's "overhead". It's simple orbital mechanics. Their orbital period is about 11hrs 58mins, and they remain visible from any given terrestrial point for 6-7 hours. Therefore, unless you're shutting off GPS service for an area comprising approximately half the earth's surface centered on the spot you want to black out (and that is clearly not the case), obviously there is some degree of directional selectivity from individual satellites.

There isn't much directivity from the satellites (only to radiate the energy towards the earth). That is exactly how they are achieving blackout ares by turning the L1 frequency off. That won't affect "half the world" as you say because there are several satellites above your head at any given time so in the blackout areas you'll only be able to receive from one or two of them.

They're not "just beacons" in the sense that any receiver with line of sight gets the same signal. They can and do use multiple antennas and interferometry tricks to affect availability. The only questions that then remain are how small an area can they black out, and can they perhaps choose to instead introduce a much worse version of the old Selective Availability random error factor to that area.

Interferometry at the size of a satellite ? At 1.57Ghz you need to control the signal phase with sub picoseconds accuracy. You can't do interferometry with multiple satellites either because you need to control distance between them with precision better than lamba/4. Actually phased arrays antennas are used only in shortwaves or with fixed telescope arrays. The only way to improve directionality in space is by using a higher gain antenna.

Let's say you have a very directional antenna with a 3deg solid angle (no such thing exists though). The satellites are cruising at 12600 miles from the surface. At that distance 3 degrees is a spot of 660 miles on the earth surface (which I think is a little more than the Pentagon surface).

Russians using GPS

[Thagg]

I was fairly astonished to see in the recent issue of Aviation Week that Russia is now building GPS-guided bombs. Presumably this is just using the civilian signal, which could be disabled or degraded in a conflict theater -- but still, it was an fairly amazing development. I suppose that it's conceivable that AvWeek got the facts wrong, and that it was a GLONASS-guided bomb, but they're usually pretty good about that sort of thing.

Thad Beier

Re:Russians using GPS

[Kjella]

I was fairly astonished to see in the recent issue of Aviation Week that Russia is now building GPS-guided bombs. Presumably this is just using the civilian signal, which could be disabled or degraded in a conflict theater -- but still, it was an fairly amazing development.

I would be very very very surprised if the Russians haven't been able to get their hands on a military GPS locator and picked it apart. Sure, the US can still turn it off but then it's lights out for everyone. Isn't the civilian signal rather useless at high velocity? I remember reading something about the military GPS sending on several frequencies, that greatly improved accuracy for missiles and the like.

Re:Russians using GPS

[everphilski]

The Russians have their own GPS satellite network, GLOSNASS.

-everphilski-

Re:Russians using GPS

[ran-o-matic]

GLONASS is a GPS (global positioning system), so Aviation Week is right. One of the first examples of Russian GPS-guided bombs is the KAB-500S-E with a 1500 lb device also available.

Re:Russians using GPS

[rufty_tufty]

Yeah I'd heard about that, I assumed it was a temporary measure until the Glonass system was fixed:
http://en.wikipedia.org/wiki/Glonass

Anyone know the current state of repair for the system since the only info I can find now is the wikipedia article...

Hey by 2010 we may have 3 competing fully functional systems - but where is the money in this? Is it really all military incentive, there can't be that much money in building GPS receivers?

Re:Russians using GPS

[Dun Malg]

I would be very very very surprised if the Russians haven't been able to get their hands on a military GPS locator and picked it apart. Sure, the US can still turn it off but then it's lights out for everyone

There's no advantage to having a military GPS receiver. They're not all that different from civilian receivers. It was assumed when they designed the system that "the enemy" would procure an example of the device at some point. This is why the military channels are protected by encryption. The guidance package off a JDAM (for example) is worth diddly squat once its encryption keys expire, and in a war zone, I guarantee those keys expire very quickly.

accuracy improvement?

[spectrokid]

I read that the improved accuracy from Gallileo will be because, apart from the low-orbit sats, there will also be geostationary ones helping the low-orbit ones to determine their own position. If this is correct, just a technology upgrade should not improve accuracy that much. Anybody any numbers?

Before I RTFA

[Philip K Dickhead]

I swear it said " GPL " satelite!

Sideeffects of faults in "other" system

[FerretFrottage]

The GPS system that is really jammed in the cases you see (by the various government buildings) is the other GPS: Government Political System. That system, whether is be the Demo or Repub version always seems to have problems.

We need more GPS satellites

[Animats]

We've recently been struggling with a Novatel GPS that receives Omnistar High Precision corrections, and supposedly provides 15cm accuracy. The problem is that it needs to see at least five GPS satellites for Omnistar HP to work. Regular GPS requires only four, but the ionospheric corrections for Omnistar require some redundancy. Five sats are the minimum; six are better.

Unless you're in a very flat area, in the air, or on an ocean, you won't see five or six sats 100% of the time. 70-80% is more like it. If one of the sats is down (which happens; PRN #5, plane B, slot 4, wss down for 8 days recently), the outages are longer.

GPS uses six rings of four satellites each, with all rings in polar orbit. The four satellites in each ring are 90 degrees apart. So, when a satellite in a ring is near the zenith, it's usually the only one visible in that ring. The original design called for more satellites per ring; with six per ring, you'd always have at least two satellites visible per ring, as long as you could see to within 30 degrees of the horizon. But there was a budget cut in the early days of GPS.

Re:We need more GPS satellites

[smannell]

Where is your antennae located? Several years ago when I was a grad student in engineering I was working with multiple GPS receivers to calculate attitude information about an aircraft. My test apparatus was a PVC "airplane" on the roof of the engineering building, and most of the time I could see 10 or 11 sattelites at once, and occasionally could see 12, which I understood to be the maximum that could be in view at any one time from the surface of the earth. Also, IIRC the sattelites were numbered 1 thru 30; so at that time there were more than 24 sattelites, although I can't be certain how many were active at any one time. I don't ever recall having less than eight sattelites in view; of course there are no mountains in Kansas to block the horizon. I don't know what your application is, but if you can elevate your antennae above the ground clutter; six sattelites 100% of the time should be easy.

Re:We need more GPS satellites

[afidel]

Why didn't you get the system which supports GLONASS. If you are paying the kind of money for that level of accuracy it's generally not that expensive to add support for multisystem inputs.

How soon?

[Ced_Ex]

How soon do we realize the benefit of this new satellite? Should we be able to see results right away just from one satellite? Or will we have to wait for 2 more satellites and hope that our GPS connects to the 3 newest ones in order to get the better resolution?

Oddities On Top?

[Anonymous Coward]

What is that stuff on top? (http://www.lockheedmartin.com/data/assets/9160.jp g)

c'mon now... they gotta admit that it's done for the scifi effect.

Re:Oddities On Top?

[paradizelost]

Big Candycanes.

maybe

[CiXeL]

they figure they wont turn it off in time before they strike.

Re:maybe

[everphilski]

er... GLONASS.

-everphilski-

Re:Normal people hate linux

[Anonymous Coward]

>1% marketshare is what they were shooting for. idiot.

Fire in the Sky?

[elm3r]

I wondered what that bright, shiney orb in the Eastern sky was last night. Was a great view from here in Tampa.

Television as GPS

[tocs]

Why do you need newer and fancier GPS satellites when you can just use satellite television signals.

"modern GPS"

[Anonymous Coward]

A new modern GPS satellite, as opposed to what? A turn of the century 1900's era based satellite...

Meh

[t_allardyce]

As with everything we're moving towards a kind of distributed mesh of systems. I think soon there will be devices that not only pickup GPS, GLONASS (whats left of it) and when it comes, Galileo, but will also have other fall-backs such as databases of cell-phone networks, TV and radio transmitters and other satellites such as TV, net and phone. Hell it could even go as far as using a camera to read the stars, and with a built-in detailed map of the entire earth you'll most likely be able to rely on terrain matching too, and accelerometers for dead reckoning, all this stuff can be used already but a single hand-held device doesn't seem far off. The US is really bitching over nothing with Galileo.

Dammit!

[Anonymous Coward]

I was hired to work at Kennedy Space Center just before Discovery went up. Since then, we've put up 3 spacecraft and I haven't seen a damn one of them. I didn't have security clearance for the shuttle and I didn't even know about the one today! Oh well, Nov 3 we try again for that GOES satellite. And March 4 for STS 121... right? guys?

GPS Sat antenna

[Jafa]

Some of those antennas also serve to detect nuclear explosions around the globe. For monitoring other countries' tests and as a warning system. Here's a pretty informative overview on the history of GPS (in pdf).

Man, I dig gps. Used LORAN quite a bit growing up fishing. Useful, but not nearly as easy or informative. Cool.
J

Carmack beat the russians...

[malakai]

... to a guided missle.

He's built a few generations of self-propelled ballistic miss...^R^R^R^ errr.. spacecraft.

The fact that for 50k dollars, most anyone with enough garage space and basic eletronics/metal working can build a small rock with GPS guidance, makes me glad places like the Pentagon and the Capital Building randomly fuck with civilan GPS channels.

Question is, if the Russians were not in a war with us, and using smart-munitions which used our GPS system, by not disabling it are we in fact aiding them and there for allied with them in the eyes of thier foe?

Why not deploy a couple GPS sats for mars?

[RagingChipmunk]

GPS satelites work essentially the same was as celestial navigation (sailing). You note the time and angle to a star. That produces a very large circle of possible locations where that star could be seen, at that time. Then you do the same with another star, which will also give a large area of location solutions - but there will be a narrow overlap where someone could see both stars, at the given angles, at the given time. Now, you do the same with a third star. You've narrowed your position on the earth to square miles.

With further degrees in accuracy of angular measurement, and time you can further reduce it to square yards... feet... inches. More stars make for faster solutions. All you need is local time & clear skies!

The same works with GPS satelites. Instead of visually seeing them, you detect them with a radio signal. Since they're geo positional, once you have "heard" from a satelites its the same as sighting a star. With three satelites "heard" you have a narrow overlap of solutions. The "magic" of GPS is that you dont need the variable of local time - its encoded into the radio signal. So now you have a completely self contained solution. The "millitary" aspect of GPS is simply adding variable length encryption to the time signal - such that the time stamp's accuracy affects the solution set of positions (less accurate the timestamp, less accurate the location).

To deploy GPS on mars, you'd need at least 3 satelites above the horizon at any given time. An ideal solution is to deploy 1 satelite every 15 degrees along the equator, and every 15 degrees around the pole - making a mesh. In practice thats way too expensive, so you make assumptions about working area (north/south hemisphere), approx range of latitude/longitude, and set up the "Lookup Table" to coorespond to lapses in date/time of coverage. Six to eight satelites would give "working coverage" to one hemisphere. ...thought you'd like to know.

Re:Why not deploy a couple GPS sats for mars?

[pe1chl]

This is not really how it works.
With GPS you don't measure any angles. The satellites send the current time, and information about their location (in the form of ephemerides).
The position is determined by examining the time differences between the received signals. That is why you need 4 satellites: there are 4 unknowns (your position in 3 dimensions, and time) and to solve the set of equations you need 4 equations.
With 3 visible satellites you need to make 1 assumption (e.g. constant elevation) to determine your position. When you could measure angles, of course it would be extra information.

Re:Why not deploy a couple GPS sats for mars?

[stevelinton]

Since they're geopositional, once you have "heard" from a satelites its the same as sighting a star.

Um. Not really. GPS uses the time of flight of the radio signal from the satellite to the receiver, rather than the direction of the satellite.

Re:Why not deploy a couple GPS sats for mars?

[FroBugg]

Like others have said, GPS works on time (distance), not position. In the end that's not what matters. The real reason we don't have a system like this on Mars is that there's just no call for it yet.

We've only got two active surface rovers over there. Most of our stuff is in orbit, and in various ways these are already helping us to keep track of the rovers.

At some point we may have dozens of little semi-autonomous rovers exploring Mars or maybe even preparing equipment and material for human visitors. With any luck, there will one day be humans there. At that point we might want to put a GPS-like system in place. But until then there's just no reason to justify the cost. Getting things into orbit around another planet is incredibly more difficult than getting them into orbit around our own.

Re:Why not deploy a couple GPS sats for mars?

[RagingChipmunk]

I did not say that you directly 'measure the angles' to the satelite. I stated that sucessfully receiving the transmission of a satelite ("heard from" in posting) produces a circle of possibilities where the receiver would have to be in order to rcv that signal. That is directly an angular measurement - ie to rcv the signal you must me within 15 degrees of its antenna.

Receiving multiple satelite signals creates overlaps in arcs. The central point of the overlapping arcs is your position.

"The position is determined by examining the time differences between the received signals" and another poster claimed that "time of flight" is used to establish your position. That is not entirely accurate. Phase relationships between two satelite timing signals, and a progressive error-reduction scheme in receiving of the time stamps is used to determine position in the centimeter/millimeter range.

Even some of the electronics have not shrunk much.

[LWATCDR]

Things like the transmitters can only get so small because of the power they have to handle.

Experiment Successful

[iamlucky13]

Please note the insightful mod. I wasn't actually sure which keywords to use to get the upgrade, but AJAX, ubuntu and evolved expanded launch vehicle seem to have worked. Now the question is do I get an "insightful" in this post for using those keywords, or do I first have to earn a "funny" or "interesting" rating with the first set of keywords.

ICBMs, not bombs

[bluGill]

ICBMs are not nuclear bombs. An ICBM is a bomb (normally nuclear) attached to a rocket so it can hit a target half way around the world. Many countries work working on nuclear bombs, which is worrying. Less countries are working on delivery rockets.

China might have an ICBM now, I haven't seen any announcement that they have built one (but such things are often kept secret). Their rocket technology is up to the task of building them if they want. (And some would suggest the primary purpose of their space program is it is a way to test the ICBM delivery without getting everyone worried about the test)

Iran is on the edge of nuclear bombs, but they have no space program. Therefore it is unlikely they have an ICBM to deliver them. Or if they do it is not a visible program that everyone knows about.

I'm not sure about England. They have the ability to create them, and I know they have nukes. Generally they ride on the tails of the US though - they are too far north, and have too little land to make launches easy. (Too easy for a first strike to take out the retaliation ability)

Re:ICBMs, not bombs

[Detritus]

An ICBM is a missile, not a bomb. The warhead may be conventional, nuclear, chemical or biological.

France, China, Russia and the UK have ICBMs with nuclear warheads in operational service. Israel probably has IRBMs with nuclear warheads.

Re:ICBMs, not bombs

[Firethorn]

I knew there was another country. I was forgetting about France.

ICBM in this case generally means 'able to reach the USA from a different continent'. And IRBM's basically a ICBM's younger brother. Europe to India, etc... Iran and India mostly concentrate on SRBM's. But they are working on increasing range.

And yes, Iran has a missile program, though they're trying get the range to reach Israel more than the USA.

I think China has, known, 3-7 ICBM's capable of hitting the USA.

While a BM can carry payloads other than nuclear, the accepted payload is generally nuclear because everything else just isn't powerful enough given the cost of the missile.

Re:ICBMs, not bombs

[Detritus]

The Soviet Union was reported as having developed and deployed ICBM warheads for the dispersal of weaponized smallpox virus and other biological agents over American cities.

Re:ICBMs, not bombs

[Firethorn]

And this was after they had literally hundreds to thousands of nuclear ICBMs.

Once you have hundreds of nuclear ones, then you can start with alternates.

Ionospheric Corrections

[Detritus]

I thought that the new features on the upgraded satellites included additional carriers (L2-C/A and L5) for civil use, which would allow for measurements of frequency-dependent ionospheric delay.

See GPS Modernization.

Re:Ionospheric Corrections

[Animats]

I thought that the new features on the upgraded satellites included additional carriers (L2-C/A and L5) for civil use, which would allow for measurements of frequency-dependent ionospheric delay.

Around 2010-2013 that should become possible, as enough new sats are launched.

GPS v2.0

[Anonymous Coward]

GPS v2.0 - Now with military grade missles!

No crappiness here

[RebornData]

It's a Garmin unit + the nRoute software, and it works quite well. One of my favorite gadgets, in fact... cost $115 and blows away all the in-dash units I've seen feature-wise. Locks very quickly, and works in areas I've had trouble with when I used to rent Hertz cards with the Magellan system.

One of the features is an infinite "track" memory, and out of curiosity I just turned on the mode where I can see all of the tracks I've ever made. Near the Pentagon, it does jump from road to road, since I do have the road-lock mode on (very helpful in areas with poor reception, like downtown).

What's fascinating is that all of the tracks I have near the pentagon driving on that one particular road show almost the exact same pattern of deflections...I think there are four tracks, but it's hard to tell because they are on almost top of each other, even when they seemingly show my car teleporting back and forth 300 feet between roads. So it's not an entirely random displacement, which makes more convinced that it's purposeful.

And BTW- it doesn't happen on I-395, which is what you're likely driving on if you're in DC from out of town... it's a local road 110 that runs between the Pentagon and the Potomac. Not sure why that would be... 395 actually passes closer to the building. But... there is more equipment / mysterious installations on the 110 side.

-R

Re:No crappiness here

[Anonymous Coward]

RebornData: You don't have a gyro or any other form of secondary nav input on that POS. 110 is a concrete canyon compared to 395. Your GPS signal is going to be slightly less than accurate in these circumstances. I used to use a laptop and a GPS, back in the days of Selective Availability, and then after. The removal of SA did make my setup more accurate, but I'd still get weird jumps every once in a while. You will as well. It's the nature of the beast. Deal with it, don't blame the Feds for your shortcomings.

Not quite

[Anonymous Coward]

No, time servers wouldn't crash immediately if GPS were switched off. One of the side effects of running an NTP server is you get a drift file, which lets an NTP server correct the local clock oscillator's output. So if you lose an stratum 1 server, the stratum 2 servers can idle on on their own for quite a while.

Confusion about GLONASS vs. GPS

[w9ofa]

You are confused.

GLONASS is a GPS system, but it is a seperate and not directly
compatible with the American GPS system.

The grandparent was expressing wonder at the fact that the Russian military would use an American GPS system for its guided bombs. GLONASS has been having problems with achieving full satellite coverage, and thus is less reliable than American GPS for Russian battlefield targets. It is also possible that the new Russian bombs have both systems for redundancy.

There is a certain measure of irony in this, if it is true.

There's always a non-technical solution.

[modecx]

That's no problem, naturally. So what if they can find the transmitters? Put the jammers in churches/mosques, in heavily populated civilian areas, orphanages, POW camps, etc. Sure, you can blow all of those things up from a thousand miles like it were nothing, or you can try to send troops in to capture it--and in a time when you need your GPS to bomb stuff, you're all too likely to get your boys massacared. It would be very easy to use our own politics against a country like ours, in a war like the one we're in. Too fairly, if we blew all sorts of elementry schools because of GPS jammers, well, whoever was ultimately responsible for the command should be hung...But not before being raped with a 12" spiked dildo.

Re:There's always a non-technical solution.

[topham]

Drop 20 GPS guided bombs over the target, if GPS is jammed they will do what, go up?

You strap a GPS unit onto a bomb and let it control the fins to guide it to it's target, but it will still hit the ground and explode. You won't be as effective as you had hoped, but I wouldn't want to be in the area.

As others have said, the bombs guided by GPS have the receivers in the rear (facing up as the bomb falls) and can therefor be shielded easily from most types of jamming.

As for blanketing a city block and thinking your safe, well, that won't do much good either. A Satelite image which is geo-referenced is accurate enough in a pinch. As others have mentioned, a laser-rangefinder will get you co-ordinates from a good distance away if you need it as well. Likely outside of jamming distances of the military signal.

We were able to wage war without GPS technology, its only more effective when it works. There are very few realistic scenarios that GPS technology could make worse. (Intentionally skewing the signal such that a specific target were hit instead of the intended target is an order of magnitude more difficult than simple jamming, and without the encryption codes only effective against the civilian frequencies.)

yes, but

[RMH101]

now jammers are so cheap, you can simply dispense a lot of them around an area, or airdrop them. sure, they'll be targetted and destroyed, but if they're cheap and plentiful enough, you still manage to jam GPS...

No Confusion

[ran-o-matic]

I fully understand that GLONASS is not compatible with the American GPS. I was just pointing out that GLONASS is A (as opposed to THE) global positioning system. Since GLONASS is not complete right now, the testing on the bomb was done with the American (Civilian) GPS, but the final product will be GLONASS guided.

Yes, this is true..

[modecx]

No doubt, I wouldn't want to be any where close to a bombload of 500lb JDAMS, because hell is going to be let loose. Nobody sane would want to be there. And therein lies the problem, we love to send in embedded reporters. If all those bombs don't hit the target, and instead hit heavy civilian populations, there's gonna be a circus. Some of our armament aren't just bombs. There's missles that pretty well require GPS, and lord knows how our forces love to use those.

Inertial guidance is great, especially as a supplement to GPS, but it's not quite to the level where it can accurately guide a "flying" bomb the several miles they're capable of, let alone a cruise missile over several hundred miles. It will hit close, if GPS was jammed for the whole flight, again close than I'd like to be, but it could be off by a hundred yards--which is no good if you're gunning for SAM sites or tanks, or other hardned targets. Probably dosen't matter too much if your targets are people or buildings.

Re:Yes, this is true..

[Dun Malg]

Inertial guidance is great, especially as a supplement to GPS, but it's not quite to the level where it can accurately guide a "flying" bomb the several miles they're capable of, let alone a cruise missile over several hundred miles. It will hit close, if GPS was jammed for the whole flight, again close than I'd like to be, but it could be off by a hundred yards--which is no good if you're gunning for SAM sites or tanks, or other hardned targets.

FWIW, cruise missiles and glide bombs (e.g. Tomahawk, JSOW) only use inertial/GPS nav to get near the target. Terminal homing is generally done via imaging infrared.