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Busy Signals for Deep Space Experiments
lionchild writes "Just when you hated getting those 'Network Busy' signals on your Cell Phones..imagine what it's like to deal with communications in deep space after all these years of putting satellites and probes out there into the space lanes. Check the article out on space.com
" The saddest part is the poor state that the deep space network of dishes is in, with some of the 70 meter antennae approaching their fifth decade with no repair funds on the horizon.
Someone ought to tell those folks over at Space.com that the word antennae applies only to the sensory projections of an insect.
When you're talking about radio receivers, the plural of antenna is antennas.
It's in the dictionary if you don't believe me.
+1 informative?
The gravitational force is proportional to mass, but goes inversely squared with distance. So any local effect of a gravitational field on a light beam will diminish very quickly with distance. There is no 'light horizon' for the solar system. You could just as easily say that there's enough stuff out there to pull the light beam away from us.
Complete bunk.
I'm breaking up? ... Can you hear me now? ... Can you hear me now?
sig.
I know stuff breaks down, but these satellites are just up there. There's no wind or water to wear down the antennas. How much do these things actually break?
Yeah that seems to make sense... ummm but you forgot the fact that the gravitational effect of mass is proportional to distance so the farther away the light got the lesser the effect of gravity. If many physicists (and they have a degree instead of a nickname;) believe that the universe is expanding fast enough so that the effect of gravity is decrease fast enough so the universe will NEVER stop expanding I think your "Solar System light horizon" *snicker*, maybe we should just call it an anti-event horizon, is a figment of your little troll infested imagination.
I stole this Sig
How many can be suprised about this phenomenom? We live in a very self-centric society that is more concerned about our own interests, unless if those interfere with ours. This is a widespread attitude in this country, reaching from the common man concerned about the television programming that those satellites are beaming down and obscuring some of the DSN antennas to those at NASA and the NSA, who have also put a great many objects into orbit, including those that are taxing the system beyond its capacity.
Scientists could continue to exacerbate the problem, as many have personal ideas about what is more important, their future NASA rovers or an improved method of keeping in contact with other projects. Funds diverted to repair and upgrade generally means that funds are diverted away from their projects, and few would readily give up funding. One of the ways to gain support for expansion and repair would have to convince people that investing in this now will have definite benefits in their projects later.
You zap the moderators with a wand of humor! The moderators resist!
Just put Ham equipment on those things, and let us do the rest...
I'm sure we could get something to work.
-twb
Meant as a response to http://slashdot.org/comments.pl?sid=33380&cid=3606 402
re-posted there. Parent = -1 redundant
Ssssh! Don't tell these things! If NASA can't define the condition of the Deep Space Network as a 'problem', funds will never be allocated for a fix. "Oh, you have a workaround," Congress observes. "Then, the problem is already taken care of. Let's move on to the next item on the budget."
Shutting down free speech with violence isn't fighting fascism. It IS fascism!
The number of options for contacting a deep-space spacecraft (which includes anything beyond geo-synchronous orbit) are surprisingly limited - basically NASA's Deep Space Network, NASA's Tracking and Data Relay satellites, and then whatever time can be purchased on the various radio telescopes and ground stations around the world. For a spacecraft at Mars the signal is weakened by an inverse square factor of billions relative to near-Earth satellites, so you need highly directed large and sensitive receivers to hear anything. NASA has been upgrading the TDRS satellites but they aren't much use for really deep space missions because of their limited size. Except for commandeering Arecibo, the 70-meter DSN antennas are about all that's available right now...
Energy: time to change the picture.
"We're sorry, please try your call again later."
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... "3rd ring of Jupiter."
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"All circuts are busy, please try your call again later."
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"Hello, Verizon information. What City and State please?"
-- "Government is the great fiction through which everybody endeavors to live at the expense of everybody else."
How's ET supposed to phone home now?
"We call it the traffic jam," said Bill Blume, mission design manager
We call it the slashdot effect.
What an interesting way to say "Right now, they're 30 years old."
IF you get a fast busy, its the network saying it doesnt have any open voice channels, too congested. Only happens in areas where there's heavy usage.
Every tower only has so many channels available, or if it's CDMA, the ability to support only so many calls. If it runs out, it just tells your phone "No go", and your phone generates a fast busy.
The Deep Space Network (DSN) works well in a crisis mode, or when a spacecraft is doing something spectacular. It's not so good at the mundane day to day.
I used to work there, and then I worked for its "competition" in the US government. The DSN does a lot of non-criticial stuff that could be done cheaper elsewhere, either by other parts of the US government, or abroad, or by private industry. It has always been unwilling to off-load any of these routine tasks, even if the charge would be a fraction of what it costs the DSN to do it.
So I am not entirely sympathetic, at least until the DSN restructures and reinvents itself.
"(a) Photons are massless, so you can't use newtonian gravity F=GmM/r^2 to compute gravitation effects on it.
:>
I trust that you are not saying that light is not affected by gravity? The mass of photons is debatable, but it is a well known, observed fact that light is indeed affected by gravity."
It is indeed observed. In fact, this was one of the first things that 'proved' the Theory of Relativity. An expedition to Africa was made to observe the sun during an eclipse. If photons were affected by gravity, then the light passing near the sun (which is normally drowned out by the sun's light, but isn't drowned out during an eclipse) would be distorted. Well, the distortion was observed.
"Never, never suspect the dreams within the dreams of dreaming children." ~The Amazon Quartet
>(a) I trust that you are not saying that light is not affected by gravity? The mass of photons is debatable, but it is a well known, observed fact that light is indeed affected by gravity.
:)
Light is bent by gravity. But not according to Newton's Law. Light follows null geodesics (a technical term : imagine space-time being curved and the shortest line between two points, called the null geodesics). To compute gravitational lensing effects, one has to use the full general relativistic equation of motions, where Newton's gravity is just an approximation.
>(b) Sure there is. Everything that has mass exerts a gravitational pull. It may be small and far away, but that don't mean it doesn't exist! As for the planets, well, they don't crash into 'us' do they? It ain't just centripital force keeping them out there...
Of course they exist, just not strong enough to have an effect on us. Now you ask : why don't everything crash into us. The answer is twofold : stuff in a galaxy (and in fact around the local galactic cluster) will eventually crash onto each other. That includes all the stars in our galaxy. However, the other stuff outside a certain distance scale (larger than a few 10s of Mega Parsecs : depending on the matter content of the universe), *might* not collapse if the universe keeps on expanding forever. The search for the exact scale is an area of ongoing research.
>(c)A light horizon exists in 3 dimensions and only because of the curvature of the earth (or other solar body). An event horizon exists in 4 dimensions. They are two different things. The same goes for a future light cone [caltech.edu]. It exists in the 4th dimension.
Everything you said is roughly correct (plus/minus semantics). Although it is completely unhelpful to think of light cones and horizons existing in 3/4 dimensions (eg : a light cone is defined by the zero norm of the metric, which has both time and spatial coordinates in them). So what's your point?
>The bunk debunker has been debunked..
Are you sure?
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The space shuttle is well armored. Yet when the thing was origionally designed, nobody knew how common high velocity (but tiny) rocks would be up there. It turned out that the shuttle had insufficient armor to deal with micrometeorites for very long. That is why you see clips of the shuttle 'flying backwards' while in orbit. There is more armor on that side...
"Never, never suspect the dreams within the dreams of dreaming children." ~The Amazon Quartet
To whom is the fee to be paid? Since there doesn't seem to be an organization with the available means/authority for decommissioning I suggest the fee be remitted to myself.
I think a more plausible less big-brotherly approach would be an international agreement where all parties would design their spacecraft to burn up/leave orbit/whatever. Part of it could be technology sharing where the more developed space programs share the how's and whatnots involved with ensuring a controlled re-entry that won't squish anyone.
Of course, you wouldn't put it past ham radio people to build their own 70-metre dish if they really put their minds to it :)
Any sufficiently advanced technology is indistinguishable from a rigged demo
--Andy Finkel (J. Klass?)
I once read an article about how much of this was going to be solved by the use of a real deep-space communications network. The idea was to have them launch some relay satellites at some stable orbital points in the solar system, and instead of having ground stations here dedicated to communicating over these great distances, you'd ideally have a relay near your probe relay its transmissions back to earth. Once you get into deep space, you can start using more efficient optical methods for communicating between relays, and communication from earth basically just relies on your ability to get the message to the nearest relay satellite and let it route your message appropriately.
:/
All of this has the added benefit of allowing all of the various probes and interplanetary craft to be in communication at the same time.
Unfortunately, aside from the original paper I read, I haven't heard of anything more about these ideas. It's possible they've been tabled as too expensive for now..
It's a shame because I think this project would be really fascinating and could probably save a ton of money in the long run.
Hate to state the obvious, but always beating our chests with the "there is no money for science" theme is not bound to generate sympathy, especially when the poor and old DSN has just received the money to build a new 34m dish at the Madrid station.
:-(
Why not reading the article before spitting out the old song about money and science? Have you considered what state is the Russian deep space network now ? tracking is available only above Russia (which is probably 14 timezones, but is still barely 1/2 of what the DSN can do) and the mighty fleet of tracking ships has been sold for scrap metal. Heck, Russia can't even track objects in Earth orbit for the full span of the orbit! So think before posting!
-Muad'Dib
PS: If instead you told me that some of the 400bln tossed by Bush IInd in the Pentagon's budget could be spent better than just in funding the "military/industrial combine" Eisenhower was scared of, I totally agree. There is no match militarily for the US, but they *have* to spend 400bln in things that do not increase homeland security - why ? well, simply because the weapons/defense industry is filling the pockets of a congressman near you....
--- "I didn't think anyone would understand it" -Prof. Bob Muller
CF is ok, and I'm experimenting with MySQL, which seems to be fairly nice. I need to do some side-by-side comparisons to be sure, but it looks as though on most things, it's much faster than M$ SQL. Anyway, there are plenty of jobs available for those who know SQL, so if you don't know it now, learn it. Have fun, folks :)
-- "Government is the great fiction through which everybody endeavors to live at the expense of everybody else."
RA and dec are also mounted on what is commonly called an equatorial platform, meaning that the platform is offset so it can turn in synch with the rotation of the earth via a single drive while pointing at the same object. I'm not sure, but I think it's the declination axis that does this. Altitude (elevation) and azimuth must both alter at varying rates to track a celestial object. That being said, equatorial mounts are much larger and more expensive than alt/az ones, so many big scopes nowadays use the simpler mount with computer control to do the tracking.
In short, both alt/az and equatorial (RA/dec) are pointing strategies, but RA/dec is a coordinate system.
"Laser light buckets could allow faster data rates than the biggest radio antennae on Earth, Miller said, but it does have its drawbacks.
"The concept looks very promising from a cost standpoint...but it can't get through clouds at all," he said, adding that to be effective, a number of ground sites would be needed to account for bad weather. "And it would all have to be developed from scratch, but it's possible that sometime in the next decade we could be using optical instead of radio frequencies."
"
"but it can't get through clouds at all"
Why can't we just use satellites to receive the 'optical' data and retransmit via radio or whatever the last 'mile' kinda like a DSL for deep space transmissions...
A fool throws a stone into a well and a thousand sages can not remove it.
For those to young to remember, the ALOHA protocol was the inspiration for the Ethernet protocol.
The bitter lessons of a veteran coder: http://bitterprogrammer.blogspot.com
If you're really interested...
The Lunar Embassy is the place you're looking for. If you want to actually be involved in getting there, you might consider joining the Moon Society
Energy: time to change the picture.
A light horizon of an event A is the spatial distance travelled by photons (or any massless particle) sent at opposite directions, from event A at time t_0 to some time later t_1. The horizon traces out the light cone in a spacetime diagram.
There are other horizons (this is semantics though). Send a couple of particles from event A, but if these have mass, they will travel at a slower velocity than light, they will trace out a smaller horizon.
Essentially, the light horizon defines the causal "reach" of event A. So you might hear people call it the "causal" horizon of some event.
The curvature of the earth, of which I take what you mean is the curvature of spacetime caused by an object of one earth mass, does not define any horizon, except for the fact the earth is there. So its existence traces out a future light cone. For example, if the earth blows up at event A, then people within the future light cone of A will eventually realizes the earth is gone. This is not as obvious as it sounds, since spacetime itself is not static (as in special relativity), but itself has dynamics (for example the expansion of the universe). There will be regions in spacetime where the light cone from event A will never reached. The line which separates the region "reachable" by event A and those that is "not-reachable", for eternity or at least to the end of time if the universe is a close universe, is called the "event horizon of A".
A more common "event horizon" is the event horizon of a black hole (i.e. some event that occured within the event horizon will never reach the "outside"). But we don't need black holes to have event horizons.
All this discussion, of course, have nothing to do with the my original post on the completely wrong statement of the debunker.
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