Military Satellite Goes Civilian

Space may be the final frontier, but that doesn’t mean we all get to explore it. Except, perhaps by radio, as the US Air Force has just demobbed a satellite and handed it over to the public to use. FalconSAT-3 was built and used by students at the US Air Force Academy (USAFA) as part of their training, then launched into orbit in 2007. It’s still going 10 years later, but the USAFA is building and launching more satellites, so they don’t need FalconSAT-3. Rather than trash it, they have turned off the military bits and and are allowing radio amateurs to use it.

FalconSAT-3 is a 120-pound satellite that is in a 469 km high orbit. It was one of the first to use a gravity gradient boom, where a weight on the end of a pole uses the gravity of earth to keep the antennas pointing towards earth. Although all of the really interesting military stuff is now turned off, it is now working as an ARS digipeter with a 145.840 Mhz uplink and a 435.103 MHz downlink. The receiver is, by all accounts, quite sensitive, and the transmitter has a 1.25 W continuous power rating, so it should not be too difficult to hear and talk to. Several amateurs have already reported successful communications, so it looks like it is open for business.  Amsat also has a good guide to the basics of getting in touch with this satellite. 

33 thoughts on “Military Satellite Goes Civilian

    1. Is that what this is?

      The article says “ARS digipeter”. Is that a typo?
      The article talks about it like it is a packet radio based bbs. But, it does say “The broadcast callsign is PFS3-11, and the BBS callsign is PFS3-12, Unproto APRS via PFS3-1.” What is an “Unproto”? Is this a packet bbs, more like the old AMPRNet but using some part of APRS called an Unproto? Or is it just APRS? I am very confused.The recommended software from the FalconSat page is not any of the usual APRS clients that I am familiar with. I cannot download them though, their ftp site does not seem to be responding. Googling WiSP brought me to a page about a program from 1993 that was specific to some sort of packet over satellite. I’ll check out the Linux programs at home later.

      Maybe I just need to set up a receiver and see what this thing is!

      1. It’s an APRS digipeater and a store and forward packet BBS. 9600 bps, so using a scanner and line in on a computer will be difficult (if possible at all). Kenwood’s line of APRS ready HT’s and mobile radios will all handle FalconSat-3 APRS messaging right out of the box, but there is a learning curve associated with it. The sat works full duplex (cross band) which complicates things (compared to PSAT and ISS digipeaters), and you must perform doppler adjustments on the downlink (70cm) band.

        1. I had to think about that a minute to see why it is difficult. Yup.. 9600 is fast for that. My understanding is that unless it has a special port that is meant for such data you have to open the radio up and tap it somewhere before the discriminator circuit otherwise there isn’t enough bandwidth. I was thinking of 2400 bps which would be much easier. That’s not really a deal breaker though. Details of exactly where to solder your wire are available for many receivers.

          I’m not sure you would HAVE to adjust for Doppler shift. Rather… if you just tuned for center frequency… you would only get a signal for a shorter portion of the pass as the frequency would be too high and low at the start and end of the pass respectively.

          Being full duplex and cross band are not important details for a receive only setup. You only listen on the downlink frequency. OTOH if you want to transmit.. two radios and two antennas are a good idea.

    2. So…..>FalconSAT-3 is a 120-pound satellite that is in a 469 km high orbit. It was one of the first to use a gravity gradient boom.

      Oh really? Uosat1 used a gravirty-gradient boom (1981!) as did UoSAT2 and several other UK satellites. The Uosats were not the first birds to use gravity gradient booms either. As best I can tell, it was first used in 1967!
      >The technique was first successfully used in a near-geosynchronous orbit on the Department of Defense Gravity Experiment (DODGE) satellite in July 1967

    1. Can you get your hands on an old police scanner? Plug that into your computer’s line in jack. I haven’t checked yet if the recommended software supports using the soundcard that way or if you have to buy a TNC (think modem but for radio instead of phoneline). If their software doesn’t support using a soundcard that’s ok, plenty of other software does.

      Anyway.. with this setup you can observer all you want but not really participate w/o a transmitter. So.. there you go.

    1. I suspect they built in some kind of killswitch to keep someone from pulling this. After all, some of the boldest hackers in the world are state sponsored. That or it’s a honeypot. :o

      Sidenote: am I the only one whose brain automatically filled in “…but it’s made in a Hollywood basement” after the first comma?

  1. HAT, AMSAT will not turn on radios that operate outside of Amateur frequencies, and they’re in control of the embedded computer on the satellite. The other features of the satellite were scientific experiments, and I believe the research regarding them has been published. There was a gravity gradient sensor, spectrometry of the plasmasphere, measurement of electronic noise in the plasmasphere, and microthrusters.

  2. Not to curb anyone’s enthusiasm. This was never a military satellite, just an amateur satellite constructed by students at an educational institution, that why it has 2M and 70 cm amateur radio equipment on board. As the AMSAT page pointed out the mission is now entering it’s third and final mission stage. In exchange for being allowed to use amateur radio allocations during other mission phases the satellite is be turned over for use by the amateur radio community, this is SOP I believe. Appears this is not going to be the old school 1200 baud AFSK simplex packet radio bird. Personally I don’t have a clue as to how difficult it will be to assemble a ground station.

  3. Doug, there were radios for NTIA-licensed frequencies built into FalconSat 3. Those frequencies are only available to government. So, it was something more than simply an Amateur satellite. Perhaps not much more, in that its missions were scientific and educational rather than military.

  4. Sodtware Defined Radio. ie mine which has been hacked to include high precision oscillator and some other unique features like a chip antenna. Its a basic RTL2832U otherwise
    Incidentally has anyone tried using a surplus piezoceramic transformer as an FM/HF antenna?

      1. It just looks like a slipped-finger typo to me. The d and f are next to each other on a QWERTY keyboard. Mistakes do happen and I’m pretty sure most of us do not put job-application levels of care into posting comments on the internet. Still.. had he actually demonstrated that he doesn’t know how to spell I would suggest that maybe English isn’t ASIANhornet’s first language. I don’t know, I just can’t put my finger on it but something gives me the idea that this may be the case. But hey… I’m sure old pros like “nigchipper” have perfect spelling in their second and even third languages right?

  5. What a bunch of know-nothing weenie hackers. I bet none of you will even try to listen to the thing, much less transmit. You look at something with bits as just another thing to try to vandalize, instead of appreciating the work that has been put into it, and enjoy the miracle of radio and satellite communications. Douchebag kiddie lulz.

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