jun 23 2002
En ngot makals historia kan vi lsa om i senaste bulletinen frn ANS. Dr psts att den gamla satelliten Oscar 7 har gett ifrn sig livstecken i form av CW-telemetri. En titt i historiebckerna sger oss att Oscar 7 skts upp den 15 november 1974 och slutade fungera i mitten av 1981. Den innehller en mode-B transponder.
Ls sjlv nedan. Sant eller inte?
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 sold 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 it s 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 it s 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]
Klla: ANS 174