AO-16 Down and Recovered

The AO-16 Command Team investigated reports this week that the satellite had gone silent. The team is aware of the anomaly and there is no cause for alarm. Control Operator, Mark, N8MH said, "Over the last month AO-16 has gone from full illumination (0 minutes of eclipse) to over 250 minutes of eclipse. Since the bird has no fancy housekeeping code running, a reasonable explanation is that the battery voltage dropped low enough to put the bird into a protected (and silent) mode."

Mark was able to command AO-16 ON during a pass over the USA. The satellite resumed operating in its 1200 BPSK digital MBL telemetry mode on the 437.026 MHz transmitter. After further testing, Mark reported, "A quick look at the telemetry suggests that AO-16 is doing fine. The current transmitter output power is about 1.5 Watts. AO-16 is again configured for voice mode and is open for normal operation."

AO-16 has occasionally turned off on subsequent long eclipse periods. Mark explained, "At about 2043 utc on 2 May 2008 I commanded AO-16 back ON again. Apparently the increasing eclipse periods require another reduction in the transmitter output power. AO-16 is now back and operational in voice repeater mode, with a slightly reduced output. It is reporting around 1.2 watts output, so it was still quite loud."

The increasing eclipse periods are too long to sustain operations at the previous transmitter output setting. The sustainable power budget is being managed empirically by Mark, with "best guess" settings using the satellite's telemetry for feedback on its performance.

When AO-16 is silent the batteries continue to charge with minimal current being drawn to sustain the vital functions of the satellite (CPU). Thus, it is in a safe resting state at the moment, and the batteries continue to charge when in sunlight. Thanks to a brilliance in design, construction, and coding, the bird is hardy and excellent at self-preservation.

AO-16 Uplink: 145.920 MHz FM
AO-16 Downlink: 437.0260 MHz DSB (LSB and USB).

After recovery of AO-16 on May 3, the current plans are to leave the satellite in the digital MBL mode for a few days so as to collect telemetry for review. You can hear the satellite "humming" in its 1200 BPSK mode.

Interested listeners of AO-16 can help by copying any telemetry captured via the Warbler sound card demodulator. This software is from the same folks that brought you the RASCAL software for Delfi-C3. A file called "warbler.kss" is produced when packets are decoded. These "warbler.kss" files can be sent to N8MH for analysis. Please include your QTH (gridsquare) and the time the telemetry was captured.

Telemetry from AO-16 in the MBL mode is random and infrequent. It's possible to hear no telemetry during an entire pass. Please do not transmit to AO-16 until further notice.

Users of AO-16 are encouraged to report any aberrant operations by either posting to the AMSAT-BB or by emailing the command team at n8mh AT amsat.org "Aberrant operations" might include the following: complete loss of signal from the spacecraft or significant change in the transmitter frequency.

[ANS thanks Mark, N8MH for the above information]

Additional information