Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!linus!genrad!decvax!harpo!eagle!karn From: karn@eagle.UUCP Newsgroups: net.ham-radio Subject: Oscar-10 update Message-ID: <1019@eagle.UUCP> Date: Sat, 25-Jun-83 03:53:14 EDT Article-I.D.: eagle.1019 Posted: Sat Jun 25 03:53:14 1983 Date-Received: Sat, 25-Jun-83 21:59:07 EDT Lines: 40 As expected, the sun sensors on AMSAT-OSCAR-10 are now beginning to function. Yesterday, initial data from the sensors indicated that the spin is very low, less than the 2 RPM lower limit at which the spin rate determination system will function properly. This spin rate was consistent with observed regular fades due to the side lobes of the off-pointed hi-gain antennas. It was also determined that the spacecraft is apparently spinning slowly BACKWARDS from the direction it should have been spun by the Ariane. This now points to an explanation in which the Ariane either did not give us the correct spin rate or did not spin us up at all. In any case, software has been loaded to spin up the satellite (in the "backwards" direction so as to avoid going through a zero spin rate) and should execute on the upcoming perigee pass about an hour from now. Spacecraft systems continue to function quite well, and there is now plenty of power from the solar arrays due to the improved sun angle. Here is a CW telemetry frame just copied from the 145.810 mhz general beacon: AMSAT OSCAR 10 at 03:30:00 UTC Orbit 19 MA 216/256 TLM: UBAT 14.5 V TBAT 4.9C Iarray 0.4A SA 0.2 dg Spin 2 RPM Satellite status: First motor firing and orbit change delayed to orbit 50 because orientation change required transponder off until then listen to this bulletin on the hour for latest news AMSAT OSCAR 10 HI HI Comments: Solar array current has not risen because there is already enough current for the spacecraft systems and the battery is fully charged; therefore the battery charge regulator has cut back the operating point of the solar arrays, reducing the generated current. The battery voltage is lower than it was during the first few days of the mission because the NiCds have a negative temperature coefficient; a fully charged battery has a higher open circuit voltage at lower temperatures. "MA 216/256" (MA = "Mean Anomaly") means that the satellite has completed 216/256 of its orbital period; perigee is defined as MA = 0, and apogee is 128. The SA (sun angle) and Spin figures are still wrong because of the very slow spin rate. Phil Karn, KA9Q/2