Satellite Back From The Dead

Papa Legba writes "Just ran across this amazing story about an amateur satellite that has returned from the dead. AMSAT-OSCAR 7 was launched in 1974 for radio hobbyists to use. In 1981 the onboard batteries died and the satellite went silent. Then on June 21st 2002, 20 years later, a hobbyist testing some new equipment made an amazing discovery. AMSAT-OSCAR 7 is live once more, both broadcasting and accepting signals. The theory expounded is that the dead battery short that took the satellite offline has cleared and it is now only running on its solar cells. While this does restrict it to daytime use, it is amazing that it works at all. " This was in the science section before - but worth the front page.

More info:

[Otto]

http://www.amsat.org/amsat/news/ans.html

AMSAT Miracle
STOP PRESS - Announcement....

First heard by Pat Gowan G3IOR, Oscar 7 seems to have made a comeback! Pat copied and downloaded CW telemetry. This information was confirmed by several AMSAT members as coming from OSCAR-7. This satellite was launched on November 15 1974, giving it a life of 27 and one half years. The receive frequency was 145.9738.

Jan King W3GEY commented, "G3IOR's telemetry frame is interesting. Apparently he did hear the AO-7 mode B beacon tonight.

"I got out my December 1974 and looked up the telemetry equations for the Morse Code Telemetry Encoder and what I found is in the attached spreadsheet.

"I'm blown away. Most of this stuff makes pretty good sense. In particular, the temperatures make sense and I would have guessed that they would be the most solid IF the reference voltage held (which it did). Interpreting some of this for those who may not understand or don't remember, the telemetry says the spacecraft was in Mode B; all the other beacons and Mode A were off. It is possible that the thing had just turned on because the old 24 hour timer just reset it to Mode B. The damn thing may think it is still on an every other day cycle. The power output of the transponder is 1.16 watts which may mean it is transmitting white noise plus beacon power. That seems about right, but a little low as I recall. The instrumentation switching regulator is in the middle of its normal range and seems to be working fine. The internal temperatures are around 15 deg. C; the external temperatures are around 5 C and the transponder PA temp, which should be the warmest - IS - it's 35.1 deg. C. The array current value is bust. I think maybe it always was. Need to look for some old telemetry to confirm that. The array current calibrations looks off. The array currents are in the normal range but all four show current. This can't be. Only two at a time should show current. Without a battery on line, this is entirely possible. The big find is that the battery voltage telemetry shows a voltage of 13.9 volts. Normal is 13.6 to 15.1 volts. So that would suggest the battery was normal BUT, the 1/2 battery voltage is measuring only 5.8 volts. That can't be. This imbalance probably means that the 5.8 volts is the correct value for the lower half of the battery (which is a low value for that half, if the cells were normal - they are probably not) and there is a break somewhere in the upper 1/2 of the battery string. My guess is the indicated voltage is really what the BCR is putting out with only the spacecraft load as a real load and the battery string has an effective break (or a pretty high resistance) somewhere in the upper half.

"So, this old war horse of a spacecraft seems to have come back from the dead if only for a few moments. And it is telling us, that even in a 1460 km high orbit a cheap spacecraft built by a bunch of hams, without very many high rel parts and without designing for a radiation dose like this, can last for 27+ years in space as far as a majority of its electronics is concerned. Even the damn precision reference voltage regulator is still in calibration!"

Like many of us, stunned by the announcement of the return of an old friend, Past President and BOD Chairman Bill Tynan added "Wow! Shades of Harry Potter and Steven King. It makes one believe in ghosts."

[ANS thanks President Robin Haighton for this item]

Seems Slashdotted...

[ONU CS Geek]

Summary Name: AMSAT-OSCAR 7 (Phase-IIB)
Nasa Catalog Number: 7530
Launched: November 15, 1974
Launch vehicle: Delta 2310
Launched piggyback with: ITOS-G (NOAA 4) and the Spanish INTASAT
Launch location: Vandenberg Air Force Base, Lompoc, California
Weight: 28.6 kg
Orbit: 1444 x 1459 km
Inclination: Inclination 101.7 degrees
Period:
Size: Octahedral shaped 360 mm high and 424 mm in diameter
Modes: A, B, and C

Beacons:

• 29.502 MHz (200 mw) Used in conjunction with Mode A

• 145.972 MHz (200 mw) Used in conjunction with Mode B and C [low power Mode B]

• 435.100 MHz (intermittent problem -- switches between 400 mw and 10 mw)

• 2304.1 MHz (40 mw) Must be commanded on. Auto off after 15 minutes. Requires STA to operate.

Linear Transponders:

• Transponder I: Mode A

  • Type: linear, non-inverting

  • Uplink: 145.850 - 145.950 MHz

  • Downlink: 29.400 - 29.500 MHz

  • Translation Equation:
    Downlink (MHz) = Uplink (MHz) - 116.450 MHz +/- Doppler

  • Output Power: 1.3 watts PEP (start of life)
    

• Transponder II: Mode B and Mode C (low power)

  • Type: linear, inverting

  • Uplink: 432.125 - 432.175 MHz *See Note

  • Downlink: 145.975 - 145.925 MHz

  • Translation Equation:
    Downlink (MHz) = 578.100 - uplink (MHz) +/- Doppler

  • Output Power: 8 watts PEP Mode B (start of life), 2.5 watts PEP Mode C

*Note: Due to changes in Amateur Service and Amateur Satellite Service there are questions as to legality of Amateurs transmitting to AO-7. The uplink frequency predates the WARC '79 allocation of 435-438 MHz by the ITU for the Amateur Satellite Service and places the uplink in 70cm weak signal segment.

Potential users should realize that when they are uplinking to a satellite, they are no longer operating in the Amateur Service but instead operating in the Amateur Satellite Service. Thus they are subject to Amateur Satellite Service rules. Therefore uplinking to AO-7 is possibly illegal since the Amateur Satellite Service is not permitted at 432.1 MHz. Also, since the IARU bandplan has the 432.1 MHz range earmarked as "weak signal" in all three Regions, it would appear that all users trying to access the uplink are also outside the Amateur Satellite Service rules and regulations.

Firsts:

• Satellite-to-satellite relay communication via AO-6.
• Early demonstrations of low-budget medical data relay and Doppler location of ground transmitters for search-and-rescue operations were done using this satellite.
• The Mode-B transponder was the first using "HELAPS" (High Efficient Linear Amplification by Parametric Synthesis) technology was developed by Dr. Karl Meinzer as part of his Ph.D.
• First to fly a Battery Charge Regulator (BCR).

Status: Semi-Operational

• The latest information is available from:
  • AMSAT News Service [amsat.org] (ANS) Weekly Satellite Report [amsat.org] (WSR)
• Jan King, W3GEY reports AO-7 is almost certainly running only off the solar panels. It is very likely to be on only when in the sun and off in eclipse. Therefore, AO-7 will reset each orbit and may not turn on each time.

Telemetry:

• AMSAT-OSCAR 7 Telemetry [slashdot.org] web page
• Thanks to Jim White, WD0E, and Jan King, W3GEY, a spreadsheet for interpreting telemetry from AO-7 has been made available in the AMSAT-NA software collection [amsat.org]:
  • http://www.amsat.org/amsat/ftp/software/spreadshee t/AO7tlmSS.zip [amsat.org]
  • ftp://ftp.amsat.org/amsat/software/spreadsheet [amsat.org]
• Please forward AO-7 Telemetry to Jim White, WD0E [mailto].

Description AMSAT-OSCAR 7 was launched November 15, 1974 by a Delta 2310 launcher from Vandenberg Air Force Base, Lompoc, California. AO-7 was launched piggyback with ITOS-G (NOAA 4) and the Spanish INTASAT. The second phase 2 satellite (Phase II-B). Weight 28.6 kg. Orbit 1444 x 1459 km. Inclination 101.7 degrees. Octahedrally shaped 360 mm high and 424 mm in diameter. Circularly polarized canted turnstile VHF/UHF antenna system and HF dipole.

Similar to AO-6. Built by a multi-national (German, Canadian, United States, and Australian) team of radio amateurs under the direction of AMSAT-NA. It carried Mode A (145.850-950 MHz uplink and 29.400-500 MHz downlink) and Mode B (432.180-120 MHz uplink and 145.920-980 MHz downlink (inverted)) linear transponders and 29.500 and 145.700 MHz beacons. The 2304.1 MHz was never turned on because of international treaty constraints.

Four radio masts mounted at 90 degree intervals on the base and two experimental repeater systems provided store-and-forward for morse and teletype messages (Codestore) as it orbited around the world. The Mode-B transponder was designed and build by Karl Meinzer, DJ4ZC and Werner Haas, DJ5KQ. The Mode-B transponder was the first using "HELAPS" (High Efficient Linear Amplification by Parametric Synthesis) technology was developed by Dr. Karl Meinzer as part of his Ph.D.

Additional information about AO-7 was printed in the September 1974 AMSAT Newsletter [slashdot.org].

AO-7 was operational for 6.5 years until a battery failure ceased operation in mid 1981. Then on June 21, 2002, Pat Gowen, G3IOR, posted this email message on AMSAT-BB:

From: "pat gowen" <[e-mail]>
To: <[e-mail]>
Subject: [amsat-bb] Re: Lazarus?
Date: Fri, 21 Jun 2002 22:30:54 +0100

I have just come across something most remarkable this Friday 21st June evening. Checking out interlopers in our 145.800 - 146.000 MHz space band with a new vertical now atop my 60' tower and working like magic, at 1728 UTC I came across a beacon at S.7 sending slow 8 -10 wpm CW on 145.973.8 MHz. It slowly Dopplered down to 145.970 MHz before going out at 1739 UTC. A full run of TLM went: -

Hi Hi
100 176 164 178
280 262 200 254
375 358 331 354
453 454 461 459
541 501 552 529
600 600 601 651
Hi Hi

It sounded VERY familiar, but, I'm dammned if I can recall which one it was. Obviously an OSCAR, but which had the callsign W3OHI? Oscar-6, 7 or 8? I think it was OSCAR-6. If so, we have a new longevity record, even beating RS-1!

The beacon peaked S9 and there were S7 burbles some 10 - 20 KHz below the beacon, FSK'ing slightly as the beacon keyed. At times the beacon took on a rough quality, wobbling in frequency, then coming back strong and quite stable again. Going by the QSB rate it had about a 1 minute spin.

Could any veteran keen observers (who might look for it) please tell me what it was, as I feel sure that any old time AMSAT OSCAR devotee may have a far better memory than I!

73, Pat, G3IOR

Jan King, W3GEY, the AMSAT-OSCAR-7 Project Manager commented:

[AO-7] has a good set of arrays and the first BCR (battery charge regulator) we ever flew. It's the first spacecraft we ever had that was capable of overcharging the battery. When the battery failed the cells began to fail short. One cell after another failed and the voltage measured on telemetry began to drop. So, the cells were clearly failing SHORT. Now, after all these years, what happens if any one of the cells loses the short and becomes open? Then, the entire power bus becomes unclamped from ground and the spacecraft loads begin to again be powered but, this time only from the arrays. Now you have a daytime only satellite but, each time the sun rises at the spacecraft you have a random generator that either turns on Mode A or Mode B or whatever it wants. So, occasionally that 70cm/2m transponder transmitter and beacon must least work. From what you have told me (and without going back and decoding the old telemetry equations) I can tell you that the following things work in that spacecraft: The arrays, the BCR, the ISR (instrumentation switching regulator), the Mode B transmitter and beacon injection circuitry, the Morse Code telemetry encoder, and the voltage reference circuitry. The latter I know is working because the last telemetry value is 651. The "6" is just the row number of the telemetry value but the 51 means that the 1/2 volt reference is measuring 0.51 volts. I know that telemetry equation by heart since it was used as the calibration value for the rest of the telemetry system. So the telemetry has a fair chance of being decoded and making some sense!!! .

The full text of W3GEY's comments are here [slashdot.org].

Initial reports on the health of AO-7 are:

• Telemetry received may be good or bad. You can determine if the telemetry is good by the 6D value. It is the reference voltage for the analog TLM system and it should be around 50. If not, then the remainder of the telemetry will be incorrect.
• Jan King, W3GEY notes that AO-7 had (has?) a very sensitive receiver and a good uplink antenna. 5 watts EIRP should provide a good downlink. Amplifiers are not required for the uplink.
• Excessive uplink power may be cause FMing of the transponder and may be causing the input voltage to the regulator that provides 6D to fluctuate causing all telemetry to be bad.
• AO-7 is almost certainly running only off the solar panels. It is very likely to be on only when in the sun and off in eclipse. Since it is resetting each orbit it may not come on every time. Reports of hearing the beacon just as it comes out of eclipse would be particularly interesting.

References

• Joe Kasser G3ZCZ/W3 and Jan King W3GEY, "OSCAR 7 and Its Capabilities," QST, Feb 1974, p. 56-60.
• "OSCAR News: OSCAR 7", QST, Nov 1974, p. 81.
• David Sumner, K1ZND, "OSCAR News: OSCAR 7 - It Works!," QST, Jan 1975, p. 49.
• "OSCAR News: Reading the OSCAR 7 Telemetry", QST, Feb 1975, p. 63.
• Perry Klein and Ray Soifer, W2RS, "Intersatellite Communication Using the AMSAT-OSCAR 6 and AMSAT-OSCAR 7 Radio Amateur Satellites," Proceedings of the IEEE Letters, Oct 1975, pp 1526-1527.
• D. Brandel, P. Schmidt, and B. Trudell, "Improvements in Search and Rescue Distress Alerting and Location Using Satellites," IEEE WESCON, Sep 1976.
• J. Kleinman, "OSCAR Medical Data," QST, Oct 1976, pp 42-43.
• D. Nelson, "Medical Relay by Satellite," Ham Radio, Apr 1977, pp 67-73.
• Martin Davidoff, "Predicting Close Encounters: OSCAR 7 and OSCAR 8," Ham Radio, Vol. 12, No. 7, Jul 1979, pp 62-67.
• "Technical Correspondence: A Look at OSCAR-7 Telemetry", QST, Jul 1980, p. 38.

The latest information is available from:

• AMSAT News Service [amsat.org] (ANS) Weekly Satellite Report [amsat.org] (WSR)

[slashdot.org] Return to Satellite Summary [slashdot.org]

Credits: Thanks G3IOR, WD0E, W3GEY, DB2OS, W3IWI.

Last update June 23, 2002 - N7HPR [mailto]

If you want to track Oscar 7...

[robslimo]

Here are the NASA 2-line Keplerian elements for AO-7:

AO-07
1 07530U 74089B 02167.52996888 -.00000029 00000-0 10000-3 0 935
2 07530 101.7955 212.2077 0012102 193.4285 166.6467 12.53558681262239

Also, you may see it's orbit here [heavens-above.com]

Um, NO!

[Andy Dodd]

The satellite is NOT in geosynchronous orbit.

NO amateur satellites are there - The cost of launch is simply too prohibitive, and it raises groundstation equipment requirements too much.

The highest-flying amateur satellites (AO-10 and AO-40) are in highly elliptical orbits. Almost all others are in various low-earth orbits, circling the Earth every 80-100 minutes.

Do a freshmeat search for "predict" - It's an excellent satellite position prediction package for Linux.

Not quite.

[Andy Dodd]

As to use of 432.1 - It's iffy.

Illegal or not, most amateurs will not transmit there as it's reserved for weak-signal work, and who knows, they might want to run moonbounce themselves sometime in the future. :)

If 432.1 were in repeater or FM simplex territory, no one would care.

Either way - The satellite has two uplinks and this only affects one of them.

Oh, and BTW.

[Andy Dodd]

To illustrate the difference in equipment requirements depending on orbit:

AO-10 and AO-40 require relatively high-gain antennas (Yagis or dishes) and tracking systems to use them.

Some of the LEO satallites, especially the FM repeater satellite UO-14 (AO-27 is the same type/orbit but runs lower downlink power and isn't on 24/7) are acessible using a $200-300 dual-band handheld with a good whip antenna. Spend $60-70 for an Arrow antenna and you can get EXCELLENT results.

2000+ mile range with 5 watts and an entirely handheld setup - Talk about cool. :)

From Ithaca, NY, I have heard a station in Mexico and one in Edmonton, AB on a regular basis via UO-14. I've even heard California.

Andy, N2YPH

I need to replace my antenna... The old one sucked and broke. Only $10 though. :)

Re:equipment ?

[LinuxKnight]

This is an Amateur Radio satellite, so you need an Amateur Radio license to work it.

See www.arrl.org/hamradio.html [arrl.org]

for a general overview of Ham radio.

Then you can set up your radios and antennas.

A page was referenced, but posted by an AC so its only at 0. Here's the link again: www.qsl.net/vk3jed/1st_sat.html [qsl.net]

As for books, look around the ARRL site, they have a vast collection of good books.

-----------
73 de K6LNX

Re:Illegal to contact dead satellites

[Nate B.]

Certainly the uplink frequency is still within US (and most other countries) Amateur Radio allocation, however within the Amateur Radio Service exists a clearly defined sub-service, the Amateur Radio Satellite Service (USA). In Part 97 the Amateur Radio Satellite Service is allocated a set of frequencies it can use. After WARC-79 those internationally agreed to allocations were changed and now the receiver of AO-7 operates outside of that segment.

While I doubt enforcement efforts would be made against the curious, it is in AMSAT's best interest not to encourage use of this bird. AMSAT is generally highly respected by the various administrations around the globe and won't jeopardrise their reputation by encouraging something that may be considered illegal by some.

I suggest you put the interests of Amateur Radio ahead of your own. If it can be shown that amateurs won't even obey the rules within their service then our chances for many significant gains at WRC 2003 and beyond will diminish greatly.

Re:daytime use?

[H1r0Pr0tag0n1st]

A good site for tracking sattilites is J-TRACK on NASA.gov [nasa.gov] A free little java app that updates satilite positions in real time and also has the ability to let you find out when a a selected sat is passing over you by entering your ZIP code. you can also access this link by going to the DR SKY website [drsky.com]. Pretty cool.