[amsat-bb] Listen for LightSail - transmissions stopped
k9jkm at comcast.net
Tue May 26 22:00:53 UTC 2015
Just read on-line at http://planet.ly/0gVop (Planetary Society) that the
LightSail satellite stopped transmitting. The team is attempting a reboot.
The telemetry data is sent on a downlink of 437.435 MHz, AX.25, 9600 bps
Excerpt from their page ...
As of late Friday afternoon, LightSail was continuing to operate normally.
The spacecraft's ground stations at Cal Poly San Luis Obispo and Georgia
Tech were receiving data on each pass. Power and temperature readings were
trending stably, and the spacecraft was in good health.
But inside the spacecraft's Linux-based flight software, a problem was
brewing. Every 15 seconds, LightSail transmits a telemetry beacon packet.
The software controlling the main system board writes corresponding
information to a file called beacon.csv. If you're not familiar with CSV
files, you can think of them as simplified spreadsheets-in fact, most can be
opened with Microsoft Excel.
As more beacons are transmitted, the file grows in size. When it reaches 32
megabytes-roughly the size of ten compressed music files-it can crash the
flight system. The manufacturer of the avionics board corrected this glitch
in later software revisions. But alas, LightSail's software version doesn't
include the update.
Late Friday, the LightSail team received a heads-up warning them of the
vulnerability. A fix was quickly devised to prevent the spacecraft from
crashing, and it was scheduled to be uploaded during the next ground station
pass. But before that happened, LightSail's automated chirps fell silent.
The last data packet received from the spacecraft was May 22 at 21:31 UTC
(5:31 p.m. EDT).
A LightSail map tracking application is at:
73 de JoAnne K9JKM
k9jkm at amsat.org
AMSAT VP User Services
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