karn@mouton.UUCP (05/16/84)
Posted: Tue May 15, 1984 8:28 PM GMT Msg: OGIE-1792-3618 From: MSWEETING To: AMSAT Subj: Oscar-11 status Oscar-11 continues to transmit telemetry on 145.825 MHz while we examine the telemetry received and investigate the reasons for the last 11 weeks of silence. The telemetry looks very good - in other words, as when the craft 'died', we have no indication of a failure mode. The only major difference is that the overall temperature has fallen from around 15c at launch to around 0c or -5 (which is close to that expected). The telecommand reliability is currently very poor on 438MHz, indeed following the one 438 command which switched the 145MHz beacon, only 4 more commands were accepted during the following 4 passes on Monday. Today (still trying 438MHz for completeness over passes under all orbital conditions) we only succeeded in successfully entering 2 more sets of 2 commands. All commands so far have purely toggled a status bit in the telemetry (the LSB in channel 61) and not had any switching effect. Efforts later this evening and tomorrow will centre on sending short bursts of commands on 144MHz. Bearing in mind that the command station 145MHz receivers will be flattenned by the transmissions, we will have to stop to see whether the commands have had any effect. [Remember that G3YJO is on holiday and that our remote receiving station is in his spare room!] Assuming no major discoveries, we will switch the 145MHz beacon to audio and digital "bent pipe" modes in the next couple of days to check the command receivers and decoders. This may tell us how to modify our transmissions to improve the command uplink performance. Note that these diagnostics will generate peculiar noises and/or digital data on the 145MHz downlink - this is expected and unavoidable if we are to sort the problems out in finite time. We will try and restore telemetry before the weekend, and leave Oscar-11 in this mode over the weekend. Please note that, due to the current state of the command uplink, bootstrapping the 1802 computer will be time consuming (at == 6-10 commands / day!) and we do not intend to do this until after the weekend. Then we will start expanding the output repertoire. Roger G8NEF