Air Force Gives 10-Year-Old Orbiting Satellite To Ham Radio Operators (arrl.org) 74
Longtime Slashdot reader Bruce Perens writes: The U.S. Air Force has transferred control of a 10-year-old orbiting satellite to AMSAT, a ham radio organization, which has enabled it for any licensed ham to use on the air, as the satellite's Air Force missions have ended. Falconsat 3's first mission was science: measuring gravity gradient, spectrometry of the plasmasphere, electronic noise in the plasmasphere, and testing three-axis attitude control using microthrusters. Secondarily it was used to train Air Force Institute of Technology students in space operations, with close to 700 cadets obtaining ham licenses in order to operate a number of Air Force satellites using ham frequencies.
Now in its third mission, control of the satellite has been transferred to AMSAT, the Radio Amateur Satellite Corporation, and all government frequencies have been disabled with only ham ones remaining. The satellite will relay APRS (position and status reporting) signals, it will operate a BBS in the sky, and will broadcast telemetry.
Now in its third mission, control of the satellite has been transferred to AMSAT, the Radio Amateur Satellite Corporation, and all government frequencies have been disabled with only ham ones remaining. The satellite will relay APRS (position and status reporting) signals, it will operate a BBS in the sky, and will broadcast telemetry.
FYI - not related to SpaceX (Score:4, Informative)
The "FalconSAT" name certainly suggests a link to SpaceX's Falcon 9 rocket, but it is actually unrelated, predating SpaceX's founding. The satellite series has used a number of different lift vehicles - FalconSAT-3 used an Atlas V 401 rocket, as part of a multi-satellite launch.
The closest the two Falcons came was the launch of FalconSAT-2, which got bumped from the Space Shuttle's manifest after Columbia. It got re-used as the payload on SpaceX's first-ever launch, the first Falcon 1 flight. Which failed catastrophically a half-minute in. The satellite apparently survived with "minor" damage, falling back onto the island, but it was never re-launched to my knowledge.
The Air Force probably doesn't need FalconSAT-3 anymore because they have FalconSAT-5, which presumably can fill a similar purpose.
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The Air Force Academy sports teams are the Falcons.
http://www.goairforcefalcons.c... [goairforcefalcons.com]
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"The "FalconSAT" name certainly suggests a link to SpaceX's Falcon 9 rocket,"
No it doesn't. The US Air Force Academy's athletic mascot and team name is the 'Falcons'.
Does your history begin in 2002?
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My history does not begin in 2002, but sports are not something I have any real knowledge of, particularly not collegiate-level sports. Even for the military academies. It's just never been my thing.
The name similarity, combined with my vague recollection of a FalconSAT on one of the Falcon rocket launches, was enough that I went to check whether there was an actual link between them. I found that there was not, and learned a couple other fun facts, and thought that it would be nice of me to share that info
USAFA, not AFIT (Score:1)
Falconsat 3 was built at the air force academy, not the AF institue of technology. '06 grad here. just google it -
https://www.google.com/search?rlz=1C1GGRV_enUS750US750&{google:acceptedSuggestion}oq=falconsat+3&{google:instantFieldTrialGroupParameter}sourceid=chrome&ie=UTF-8&q=falconsat+3&pws=0
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Why two separate bands? (Score:2)
Can anyone explain why the uplink is in the 2m band while the downlink is in the 70 cm band? Having separate frequencies makes sense, but what purpose is there to having them this far apart?
Re:Why two separate bands? (Score:5, Informative)
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Thanks for making it simple without being condescending. I don't stand a snowball's chance in hell of hitting this repeater, but I may at least attempt to listen for it.
Re:Why two separate bands? (Score:5, Interesting)
You might be surprised. It only requires the Technician class license, which is no big deal to pass. A hand-held crossed 440/146 beam antenna will make it and costs less than $100, you don't really need an azimuth-elevation rotator. You learn how to point this by hand and wave it around until you hear the satellite. The required radio power would work with a walkie-talkie but a mobile/base radio is more likely to have the input and output that works with 9600 Baud modems. I am not clear whether a 9600 TNC [wikipedia.org] works or whether you just use sound cards and a software modem.
The voice birds require that handheld antenna and a dual-band walkie-talkie, and that's all.
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I'm guessing this is 9600 baud packet, which would require a PK-232 or similar TNC.
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"I'm guessing this is 9600 baud packet, which would require a PK-232 or similar TNC."
Hardware TNCs are old technology and are now far out performed by modern sound card based modems. I have a stack of them that will probably never see power again.
Take a Raspberry Pi, a cheap USB sound card and run direwolf software and you have the basis of support for multiple low speed data modes.
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HI Bruce
Hardware TNCs, or software modems taking the signal from a soundcard from the radio's discriminator (NOT from the speaker) or software modems getting a signal from software defined radio (a $15 RTLSDR USB dongle for example) -- any will work for the satellite's 9600 baud signal.
The satellite transmits what amateurs consider a "standard" 9600 baud packet radio signal -- G3RUH modulation, 9600 bits per second, bit scrambled, NRZI, HDLC with zero bit stuffing, AX.25 packets.
Dequeue
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How hard would this be for a SDR/RaspPi combo? Seems doable, but I would need a month to study up for Tech license. At least no code, I couldn't copy 2 wpm today without a recorder... Naw, I would rather go QRP with all the cool new tech and old school technique. Or not.
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The original RaspPi probably has just enough CPU horsepower to demodulate the signal and compose the appropriate replies in order to use the onboard BBS in real time. The RaspPi3 has a better chance of working. I haven't tried it yet, but it's on the bottom of the "to do" list.
The original RaspPi certainly has enough horsepower to record the signal during the pass (say, to an attached USB thumb drive), and then after the pass it can demodulate the 9600 baud data stream out of the recording. This is fine if
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Satellites aren't that far up.
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Well they're either That Far Up (geostationary), or they're moving. I'd actually prefer That Far Up, at least I'd always know where to aim.
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I have seen people do this by hand, it really doesn't look so bad. The satellite is always going to start at the horizon at a predicted time, and then cross over you. So, you can always start at the lowest elevation that is clear, and just do azimuth with a compass (remember declination).
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As I recall, the other primary reason why AMSAT typically uses this configuration is due to doppler. The frequency shift at VHF is only something like +/- 15kHz, which is usually within the capture window of a VHF receiver, whereas at UHF it's +/- 45 kHz, which is beyond your typical receiver. Since we can retune our earth based receivers on the fly, the whole thing works.
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The equipment that is required to allow receive and transmit to happen in the same band is extremely heavy. For example see this install for a repeater [wa7x.com]. I would imagine the satellite designers didn't want to include a hundred extra pounds of cans when they could just use two different bands and not worry about it.
Re:Why two separate bands? (Score:4, Informative)
Having separate frequencies makes sense, but what purpose is there to having them this far apart?
This is standard for satellite operations.
There is one overriding technical goal in creating a working repeater. The receiver must not be swamped by the transmitter, which has a much stronger signal than anything it will hear from Earth. Earth-based repeaters (which this basically is) have physical isolation that is based on the wavelengths of the signals. A VHF duplexer [jet.com], as it is called, is about 3 feet tall and 6 to 8 inches in diameter, and there are usually four or six used. The physical cavity allows for very sharp notches and passbands that are applied to both transmit and receive. The receive duplexers selectively pass the receive signal and notch the transmit. The transmit duplexers selectively pass the transmit signal and notch the receive. The antenna end of the duplexer chain (e.g. three in series from the transmitter, three in series to the receiver) is simply tee'd together. This setup works when the signals are 600kHz apart.
You can build smaller duplexers [radiotwoway.com], such as those used for ancient mobile telephone systems, or for some current repeater systems, but these require a minimum of 5MHz separation between transmit and receive, and support lower power transmitters. There is only 4 MHz in the entire amateur 2M band (2MHz in some countries), so this separation is not possible within that band.
It is VERY easy to build an LC (coil/capacitor) duplexer [gigaparts.com] for considerable amounts of power when the frequencies are 300 MHz apart. Like VHF (146MHz) and UHF (440MHZ). This can fit in a package smaller than a pack of cigarettes. And it is much lighter (pun intended).
That's why amateur satellite operations use widely-split duplex. If it is UHF uplink and VHF down it is referred to as U/V mode, opposite is V/U mode (or vice versa. I don't do satellite ops.)
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AMSAT does handle orbit control for its own satellites, but in general no ham radio satellite is designed to de-orbit or to require periodic orbit maintenance. Rather, they are designed to operate with indefinite lifetimes in slowly-decaying orbits, and AO-7 has operated, with interruptions, for 43 years. Most Amateur satellites are passively stabilized, and magnetic stabilization systems have been used often.
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Since the AF disabled the S band and other transponders, one of which was probably for command and control, the capability of controlling it, if there was any way at all, is gone. After 10 years, I doubt that there is much in the way of orbital maneuvering that can be done, in any case. For small sats like this, they may have had a small amount of gas initially in order to place the thing into the proper orbit after launch but that probably ran out years ago. I'd suspect that the bird is fixed in its orbit
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The real requirement was that the satellite not transmit on those frequencies. There isn't any problem with receiving. A satellite with this size and cost is often built without ROM, simply because of the cost of space-qualified ROM which must be rad-hard for decades of operation. It loads its computer program into RAM using a completely hardware implementation driven by ground control with the CPU reset line asserted for the whole time. Once the program is loaded, the CPU is allowed to start. The CPU may b
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It loads its computer program into RAM using a completely hardware implementation driven by ground control with the CPU reset line asserted for the whole time. Once the program is loaded, the CPU is allowed to start.
I'm not sure what you mean here, but it sounds really cool. Could you clarify? Plz? :)
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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.
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The 1802 was pretty popular CPU for military use in the 70s-80s. Not just for space use. God, I remember that, wow.
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A satellite with this size and cost is often built without ROM, simply because of the cost of space-qualified ROM which must be rad-hard for decades of operation.
I thought it was the other way around? A PROM, and especially a mask ROM is an incredibly simple device, effectively just a single diode between a given row and column on the die. Not counting the address decoder (which you would have in both RAM and ROM), a ROM chip only has a single PN junction per bit. An SRAM cell has 6 transistors per bit, and DRAM is a capacitor plus a transistor (not to mention the required refreshing).
I'd love to be shown the error of my ways, but I would have thought the KISS princ
Slashdotted (Score:3)
I broke the ARRL web site :-). Try the AMSAT [amsat.org] site instead.
- K6BP
Strange use of hyphens... (Score:1)
Not sure whether to be more concerned at the fact that there is a 10-year-old locked in orbit around a satellite, or that control of said youngster is being transferred to a ham radio organization.
Strange...
Related to Hurricane Maria? (Score:2)
I wonder if this was accelerated because of the need for HAM operators in Puerto Rico following Maria.
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I don't think so. Red Cross asked for people who had experience with digital modems over HF radio, and VHF digital for shorter range. The satellite is usable, and we are indeed building a satellite that is geosynchronous (not geostationary) and designed for emergency communications, but satellite is probably not a major part of that operation.
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"useful easily once ever 1-3 days from a given location."
Which is still very useful for noncritical communications following a disaster.
Great (Score:2)
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" lot of those cadets go on to train for volunteer emergency communications later on."
A lot of those cadets, when deployed, will be engaging in emergency communications daily as part of their mission. They are almost over trained for volunteer emergency communications. Almost.
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If you would like to be a ham, go to this page [arrl.org] and fill out the form. The folks at ARRL will send you information on becoming a ham. Also, read this part on getting licensed [arrl.org].
There is a lot more to it than CB, and a lot of the stuff you hear on CB shouldn't ever be done on ham radio. And ham radio is not a gift. Expect to do some work to become a ham.
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3840 kHz will sure get him a mix of ham and CB.
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There's no such device, at least not in the US. Under FCC rules a radio for use on CB (11-meter band,) has to be type certified and channelized. Ham radios operate all across the amateur spectrum, (160-meters through 10-meters on HF, 6-meters through 2-meters on VHF, etc.) and require no type certification. Since a legal CB radio must only operate on CB channels, and a ham radio lacks type certification, the two services are mutually exclusive, as far as equipment is concerned. The one exception is that eve
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>the two services are mutually exclusive, as far as equipment is concerned.
And usually Hams wouldn't touch a CB rig with a 1000000000000000000 foot pole.
"If you ask me that ain't no rose, roll up your windows and hold your nose." Leyton Wainwright III
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New amateur receivers are type-certified for avoidance of the old 800 MHz analog cellular frequencies, as required by the Electronic Communications and Privacy Act in 1986. So, you will see a notice about radios not being offered for sale until they are type-certified.
I would like someone to help work on repealing that provision of ECPA. Obviously everyone uses encryption now.
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There is still no requirement that amateur transceivers must be type certified for use in the Amateur Service. An Amateur radio operator can build their own radio and use it all they want, provided they adhere to emissions standards. But, they do not have to obtain type certification to use their radio.
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However in order to be sold in the USA, they must comply with the law that forbids reception on the old AMPS bands. Of course, this is usually just a pinkyswear on the part of the manufacturers, and can be unlocked either through accessing a calibration mode, or by snipping a diode/resistor on the main circuit board.
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You can build one, but you can't sell a VHF/UHF transceiver that is not type approved, because all receivers in VHF/UHF bands are considered to be scanners, and thus must be type approved. It's not in Part 97 but elsewhere in FCC regulations.
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Ham Radio? (Score:2)
Is that something William Shatner is involved in?
How is that 10 year old still alive? (Score:2)
Which satellite are they orbiting?
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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. [amsat.org]
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Nickel-hydrogen batteries in satellites can last 40,000 cycles.
How has my Prius lasted for 10 years on the same battery pack? Because the software never discharges the battery below 20% or charges it above 80%.
Good charge management software is one thing. Also, the satellite can be designed to work in sunlight with an open or shorted battery, which is how AO-7 is still working after 43 years. AMSAT's experience in space has taught them a lot about battery failure.
In order to quailify as a BBS... (Score:1)
In order to qualify as a legit BBS, it has to have TW2002...
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Hey thanks (Score:1)
Thanks for posting this up Bruce, it's a wonderful story.
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