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The really cool thing to mention about OSCAR 7 is it died in 1981 due to a short in the batteries. On June 21, 2002, Pat G3IOR heard some telemetry of W3OHI, which was OSCAR-7 transmitting on the 2 meter band. A follow up by one of the designers decoded the telemetry and found it to be authentic.

21 years of being silent in space was long enough for the short to open and the satellite booted when light hit it's solar array. The controllers came back online and it started transmitting.

That's simply cool.

Without knowing about the specific design, a good guess would be one of two things (perhaps both). This satt is obviously a low power device with a 1 watt transmitter. So its battery requirements are not large. So they could have packed extra batteries that they could switch out every so often as one went bad. Another thing that they might could do is operate just when the sun is available, like what trustworthy Oscar 7 is doing now.

It looks like the FOX series of low-earth-orbit cubesats are using STM32 and GNU C. Here's a slide show. Because these don't traverse the van Allen belt, they don't have to be as rad-hard as higher-orbit satellites.

These are probably better than my explanation. A German space scientist, Karl Meinzer, designed this all in the 1970's and it's still being built into satellites.

• IPS AMSAT's own threaded interpretive language used in the integrated housekeeping unit (IHU) of the satellite
• Paper about Phase IIIB satellite, mentions how the IHU works with no RAM
• Experimental more modern controller

I broke the ARRL web site :-). Try the AMSAT site instead.

- K6BP

AMSAT on the bottom of this page specifies 3 programs as "Software for operating via the Packet BBS". But I see that at the moment it is open for live QSOs but not automated ones.

That's true, but the celestial spheres are an orderly place. The math to predict an orbit is fairly straightfroward. (Castor is a better link if you want more than a quick overview.) Watching it go around the body it's orbiting is like watching the hands on a clock. So I don't find it particularly strange that if there's a bunch of loose junk on an orbit that intersects us, that we'd run through it on a regular basis. I'd be more surprised if it was just random.

Let me save you some brainpower.

As an amateur radio operator, I track the ISS (and other satellites) using keplerian elements. AMSAT ones are accurate enough for the ISS:

http://www.amsat.org/amsat-new...

AO-13 was not in geosynchronous orbit, but a highly elliptical orbit with apogee near geosync distance (40,000 km), but perigee much lower (2500 km). You worked the satellite at apogee because it basically hung in the air there, and then briefly whisked around the planet to quickly to track around perigee. Transmitters tended to be 25 watts, which is more than most hand-held devices.

Folks tended to use yagi antennas with at least 15 dB gain to work AO-13 at apogee (typically 10 directing elements, here is an image).

On the other hand, I've talked to ISS astronauts with a 5W handheld transceiver and a rubber duck antenna. ISS is only 370 km away, plus it "sees" less of the planet so there is less interference from other RF sources.

Reading some threads about it yesterday, I found that some hams in Germany have priority access to a 20m dish. Woah.

The HAM are already on it, bless their souls:

http://ww2.amsat.org/amsat/arc...

If they can make it (meaning: at the very least being able to get the carrier), it will be a hack of historic proportions.

Write an article and submit to ARRL's QST and join and post to the AMSAT mailing lists as there are quite a few keys there as well. Talk to your local amateur radio club and get the word out and you might even talk to your area coordinator.

Morse code is very low bandwidth and will get through noisy conditions...like passing through the ionosphere.

You don't really need a satellite dish, just a directiona antenna(a yagi will do okay). Aiming it at the correct part of the sky is certainly important though. There are a lot of hams already doing communications via purpose built amateur radio sats, see: http://www.amsat.org/

It's hard to believe an article like this gets posted without somebody mentioning AMSAT. They've been building satellites since the 60's on a much larger scale. Help support the latest AMSAT model called the FOX-1.

It's hard to believe an article like this gets posted without somebody mentioning AMSAT. They've been building satellites since the 60's on a much larger scale. Help support the latest AMSAT model called the FOX-1.

"Antares PhoneSat Cubesat Launch Now Planned for April 21"
can be selected from the list on Right side column of this page:

+ http://ww2.amsat.org/

No solar panels => Satellites get short lives (a week or two?)

So, use 'em while their batteries last... as soon as they begin
to work. AMSAT site should have the uplink & downlink freq's
(& you should have an Amateur Radio license to transmit...)

Heavens-Above.com can tell you when to listen for the little,
battery-powered Ham satellites. (Cf Amsat.org for names.)

Let us know what you hear... & let AMSAT know, too, if you're
heard (& repeated) by one of the satellites.

Enjoy!!

>> I can't imagine that a group of amateurs would have the funds to build a satellite
You can't imagine it, but it happens since 1961
http://www.amsat.org/amsat-new/satellites/history.php

Wow. Virtually every statement in this post is incorrect.

OP, get off Slashdot and go to amsat.org

Now. Good bye.

Since this is an AC, I thought I'd repost it. AMSAT is exactly the organization you want. They are a group of amateur radio operators who have successfully built several communications satellites. Even if you choose to work with another group (or start your own), their experiences will be most helpful.

The longest operating spacecraft?
The radio amateur satellite AMSAT OSCAR 7 http://www.amsat.org/amsat-new/satellites/satInfo.php?satID=9
has been launced in November 1974 (3 years before voyager) and it still works.

Of course it has been silent for a couple of years so the entire operating period is shorter.

Yawn, phase one has been done (http://www.amsat.org/) and also takes care of the nasty problem of radio spectrum management for up and down links with the bird. LEO satellites are fine for store and forward emergency communications, but anything less than geosynchronous is going to make for some grumpy consumers. After all, first the non-synchronous satellite finally comes above the horizon far anough to be useful, then the guy serving the bountiful buffet of pr0n torrents has to shut down his server because Mom says it's time for bed. After finally hitting enough servers through enough birds (and on and on) you get the file, only to find out it's a password locked fake, It would be maddening enough to make a guy go back to stroke books.

Check out AMSAT...these guys have been building amateur communication satellites for years. http://www.amsat.org/amsat-new/index.php

I've dumped quite a bit of money on AMSAT. Most of it has gone up in smoke (literally) but it's a nice idea. I'd be much more active if I lived anywhere I could actually help build the things, so it's sort of a vicarious ? pleasure kind of thing.

OSCAR. http://www.amsat.org/amsat-new/index.php

Here's a list: http://www.amsat.org/amsat-new/satellites/status.php

If AMSAT is a valid example, volunteer work can make miracles happen on the cheap. Amateur radio folk have launched dozens of volunteer-built satellites as ballast on existing launches. They have recently started making birds large enough to be primary payloads. The money for the launches is donated.

If AMSAT is a valid example, volunteer work can make miracles happen on the cheap. Amateur radio folk have launched dozens of volunteer-built satellites as ballast on existing launches. They have recently started making birds large enough to be primary payloads. The money for the launches is donated.

send email using APRS to one of many available satellites, although you may only get a few good passes each day-
http://www.amsat.org/amsat-new/information/faqs/aprs.php

including the international space station-
http://www.ariss.net/

many APRS handheld radios are available-
yaesu vx-8r:
http://www.yaesu.com/indexVS.cfm?cmd=DisplayProducts&ProdCatID=111&encProdID=64C913CDBC183621AAA39980149EA8C6

kenwood th-d72:
http://www.universal-radio.com/catalog/ht/3072.html

I thought comm satellites were geostationary.

Not amateur radio satellites. It costs a lot of money to up a satellite in geosynchronous orbit, far more than even a bunch of hams could come up with. As a result, amateur radio satellites are usually piggybacked on commercial launches with a bit of spare capacity and end up in a much lower orbit.

You can go to the Amsat Web site for more details.

IANAHRO, but the topic is interesting. I was snooping around and I found this link which discusses equipment and antennas and has some relevant videos. This site has some info on the various ham bands that might be relevant. It mentions that the sun spot cycle is a problem right now for long distance communications that bounce of the ionosphere. From that site it looks to me like the 20 meter (14mhz) and 40 meter (7 mhz) bands are your best bet. I wouldn't want to have to rely on repeaters on mountain tops. I'd get myself a Yaesu FT-817 and plan to rely on the busy 20 meter band to bounce the call for help off the ionosphere. I'd also look into using an amateur radio satellite. Even though you only get one 15 minute window every 24 hours it's better than nothing. It seems most of those satelites work in the 2 meter band. So an FT-817 would also cover it. But it seems that a small dish antenna might be your best bet to transmit to the satellite. A yagi would probably be easier to pack though. You might also look into a helium balloon or kite aerial antenna. A very cool/geeky way to maybe get above the mountains. I wouldn't want to rely on having to summit a mountain when you have an emergency. I would assume we are talking about something like a broken leg or worse. Despite all these budget communication options if you really value your life and have some money I would go with renting a satphone.

The cubesat platform has provided a means for quite a few orbiting radio amateur experiments.

The cubesat platform has provided a means for quite a few orbiting radio amateur experiments.

I don't know about that. I've read quite a bit about "rocket enthusiasts" who are doing just that - launching rockets into space. Amateur radio enthusiasts come to mind. Something like, oh, this.

Actually, try getting a ham license and you will find plenty of equipment and help experimenting with microwaves. I regularly see TWTs, brick oscillators, http://home.swbell.net/k5oe/K-Band/K-Band.htm">K-band (24 GHz) and X-band (10 GHz) equipment in the under $100 price range. Even the old Gunn Diode Oscillators can provide some fun. Hams even launch their own satellites and send their own microwave and VHF/UHF signals to the moon and back.

Go ahead and do it. It's a great hobby, and there are plenty of different activities on bands not wiped out by BPL or this mess. You can even bounce signals off the moon and talk across the world over our own satellites!

It's not BS. Last I checked you could put 1 KG into LEO for $25K. http://www.cubesatkit.com/

Cubesats typically hitch a ride with larger projects for cost efficiency.

http://cubesat.ece.uiuc.edu/
http://mtech.dk/thomsen/space/cubesat.php
http://www.amsat.org/amsat-new/satellites/cubesats.php

Even if they all put 100,000 watt amplifiers on their wifi cards, on our end it's just jumbled garbage.

As a ham radio operator I have communicated with others on the opposite side of the planet (USA to Australia) with 100 watts. That's the same amount of power that a light bulb uses. Some hams make a hobby out of contacting as many different countries as possible with 5 watts or less. Google "DX QRP"

Hams also communicate with satellites using just a few watts.

At the frequencies where cell phones, and wifi operate, the chief distance limitation is the RF propagates "line of site." If you have a line of site path between two transceivers, it doesn't take much power.

I agree with that the revolution will likely be over before we can get the hardware to the Iranians. Also, there may be a fair amount of infrastructure that would have to be deployed to support the communications. IMHO, since wifi and cell phones are line of site and we can't just go and put up American cell towers and wifi access points in Iran, all the communication would likely have to be handled by satellite. I doubt we have enough satellite band width available to make this happen even if the Iranians magically had all the hardware they need.

Based on the description in the article, I'm guessing the sats in question use linear transponders similar to many of the AMSAT Oscar (AO) satellites.

http://www.amsat.org/amsat-new/information/faqs/langdon.php has info on some of the AMSAT satellites.

It sounds like the security of the "as designed" military system was implemented at the endpoint radios with no satellite involvement. For 1970s satellites this makes sense - keep the satellite (the REALLY expensive part) simple, unfortunately it does make the system susceptible to illicit use and jamming.

http://www.networkworld.com/news/2009/040209-obama-cybersecurity-bill.html

A federally enabled Internet kill switch will place an Internet Off Button in the White House which can be used to instantly deactivate the Internet in case of an emergency, such as the plebes getting riled up. This bill, introduced to the Senate on April Fools, is expected to pass.

The guy in the white house may soon be able to take out the Internet when those who inhabit it publish information that is embarrassing to him, but there are other methods of digital conversation, such as Packet Radio, Ham Radio satellites, and other Amateur Radio communications methods.

We will truly know that we are an occupied nation when the white house declares ham radio to be illegal. One of the first steps of any tyranny is the control of information

Would we be denying ourselves the use of certain orbits for hundreds of years?

Man! That would be annoying! No amateur radio contacts via the satellites put up there for that purpose :(

Helical antennas are quite common. They provide acceptable gain, but more importantly they are circularly polarized which is a great boon for receiving signals from tumbling spacecraft such as Amateur Radio Satellites. A strange instance of a helical antenna is the Quadrifilar Helical antenna. This egg-beater shaped beast is perfect for receiving circularly-polarized signals (from weather sats, for instance). I had one cut for 70cm on my roof for a long time.

Amateur radio satellites have a long and successful history of exactly that - being smart ballast for other launches. As long as our sat is the right size and weight and passes flight worthiness tests, we get to replace the chunks of concrete or whatever else they were going to use.

Our newest birds are large enough to require their own launch, so we've got to come up with $LOTS_OF_MONEY to launch the big birds.

From the numbers in the summary, a fully-charged one of these would supply enough energy to propel a 3300lbs (1500kg) car from 0 to 1100mph (500m/s)

Ahhh you must be from the Theoretical Physics Department, over here in Engineering we have wind resistance, friction and efficiency to worry about.

Not much wind resistance in space. This might be useful for satellite power. Certainly the lifespan of small earth orbiting satellites seems limited by nicad battery life. Capacitors would have no age limit, other than maybe leaking electrolyte all over. (Geosynch satellites eventually run out of station keeping fuel, this wouldn't help them much)

I could list quite a few amsats with burned out batteries, heres the most famous, that came back to life a couple decades after the shorted nicads failed open.
http://www.amsat.org/amsat/sats/n7hpr/ao7.html

Here's an interesting site and quote about satellite batteries.

http://www.qarc.on.ca/minoct02.htm

There are 5 battery systems that are fed through a Battery Current Regulator (BCR) at 28v. To-date they have used NICADs. AMSAT is looking at other newer types, like Metal Hydride and Lithium Ion to get more capacity at lower rate, plus the number of times a battery can be charged. They still favor the NICADs because they can be charged more often then the newer ones before they have to be replaced. Robin used slides to show the details of the satellite inside and out.

Eventually they'll deorbit and burn up, but probably not for a while. The tools were in a stable orbit when they were dropped and they weren't thrown very hard (just enough so they were out of reach by the time it was noticed). It takes quite a bit more delta-v than that to deorbit.

Air resistance will get it in a couple weeks at most.

Something the size and density of a space suit takes about six weeks to deorbit due to air resistance at the ISS altitude.

It's an interesting thing to consider, will the much smaller tool bag with its vastly inferior surface area to volume ratio compensate for the (probably) higher density of the tool bag? It is smaller, so it should deorbit much faster because it has much more surface are per volume thus more air drag. On the other hand, the metal tools in the bag are probably somewhat denser than an old space suit.

The ISS has about a pound of force from air resistance, roughly. The toolbag has probably a thousandth the surface area, but probably only a millionth the weight. So it'll probably deorbit about a thousand times faster than the ISS. I am guessing this guess is only accurate to maybe two orders of magnitude.

I'm heard that a hot air balloon (just the fabric canopy) would deorbit in about a revolution due to air resistance, whereas a steel I-beam, pointy end forward (good luck due to gravity gradient stabilization) would not deorbit for decades. That claim that I heard is probably off by even more orders of magnitude.

See link below about the suitsat launched from the station, pictures, how long it lasted, etc.

http://www.amsat.org/amsat-new/articles/SuitSat/

That's because the url in the article is wrong. AMSAT is http://www.amsat.org/

But a cellphone cam might just work.

A cell phone CCD will be about 20 grams. But you also need the decoder, the DSP, and the transmitter, and the battery. If you still manage to do all that, then what's the use of a low-res image from 400 km? I understand that it might be cool once or twice, but that's what amateur satellites are for (this includes ham and non-ham ones.) These satellites don't weigh 20 grams - they are larger, but they actually work.

Usually amateur satellites hitch a ride on some other commercial launch, for a fraction of cost. There is no need to invent yer own rocket for $2,000 - use already developed hardware that works for real. Besides, rocketry is not a safe hobby when you deal with enough propellant to lift something to an LEO. When you try to do it on the cheap things only get scarier.

On subject of RC planes: a half a gram RC plane only needs to receive, so its power budget is not as tough as a satellite that has to have a large antenna and/or a powerful transmitter to send its status and data back to Earth. But half a gram RC plane is still an achievement, and it is useful because you can fly it and enjoy its flight. People are free to make a 20g satellite also, but it will be far less useful than a tiny RC plane.

You could also:

• Communicate over satellites. There are many Amateur Radio satellites in orbit, and a BUD is great for talking to them: http://www.amsat.org/amsat-new/index.php
• Communicate via the earth-moon-earth path (EME, AKA moonbounce). http://en.wikipedia.org/wiki/EME_(communications)
• Downlink NOAA weather satellites.
• Do radio astronomy: http://www.signalone.com/radioastronomy/telescope/
• Cover it in foil and have the worlds biggest solar hot dog cooker.

For sure. AO-51 weighs 11kg. That's about 24lbs for you Americans. Have to buy a beam, and then I can work it

The Amateur Radio satellites went to an Ethernet backbone some time ago - over a decade IIRC.

From the detailed description, "AMSAT-OSCAR 7 contains two basic experimental repeater packages, redundant command systems, two experimental telemetry systems, and a store-and-forward message storage unit. The spacecraft in solar powered, weighs 65 pounds, and has a three-year anticipated lifetime.... AO-7 became non-operational in mid 1981 due to battery failure . In 2002 one of the shorted batteries became an open and now the spacecraft is able to run off solar panels. For this reason it is not usuable in eclipse...." and elsewhere, "Redundant command decoders of a design similar to the unit proven highly successful in OSCAR 6 will be flown. The decoder has provisions for 35 separate functions...."

The telemetry system is operational; the command system is partially operational.