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KP4IG > SAT 01.02.04 01:33l 83 Lines 4276 Bytes #999 (0) @ AMSAT
BID : ANS-032.03
Read: DB0FHN GUEST
Subj: AO-40 in Critical Condition
Path: DB0FHN<DB0RGB<OK0PPL<DB0RES<ON0AR<WB0TAX<KP4IG
Sent: 040131/2327Z @:KP4IG.#JD.PR.USA.NA #:36603 WFBB7.00i $:ANS-032.03
From: KP4IG@KP4IG.#JD.PR.USA.NA
To : SAT@AMSAT
AMSAT News Service Bulletin 032.03 From AMSAT HQ
SILVER SPRING, MD. February 1, 2004
To All RADIO AMATEURS
BID: $ANS-032.03
Sunday, 25-Jan-04: On orbit 1486 AO-40's battery voltage dropped momentarily
to 24.5 volts at MA=132, triggering a "LOW" voltage flag and shutting off
the passbands. The torque command has been updated to decrease ALON
slightly and improve solar angle. At the beginning of the eclipse on orbit
1486 at MA =225, the battery voltage rapidly dropped just below the S2 Tx
cutoff voltage of 24.0 volts and the S2 Tx shut down to protect the battery
and IHU's.
Monday, 26-Jan-04: KU4OS published two charts from a recent K-Block of WOD
showing the Main Battery voltage starting at MA 154 on orbit 1485 and
showing the events of orbit 1486.
Serial Orbits: http://home.cfl.rr.com/lmclamb/ao40mb04jan.jpg
Orbits aligned by MA: http://home.cfl.rr.com/lmclamb/ao40battstack.jpg
Tuesday, 27-Jan-04: Last night (Orbit #1488, 2004-01-27, 00:57, UTC MA 42)
the battery voltage suddenly dropped from 26V to 14V. We currently believe
that in some kind of domino effect more battery cells died shortened.
Telemetry shows that about nine minutes later the Heat Pipes 4+X+Y
temperature suddenly rose from 27°C to 92°C. This is probably a sensor
anomaly. Command stations are trying to send blind commands to the
spacecraft in an attempt to switch over to the auxiliary battery. We have a
good "fix" on ALON/ALAT and we are spinning at 3.5 RPM, so we have quite a
few weeks before the squints become problematic due to the mystery effect.
Currently, the mystery effect is working for us to improve solar angle.
Attempts will also be made in the next few days to bring the K-Tx on line
and search for its signal.
Wednesday, 28-Jan-04: All signs point to a catastrophic failure of the main
battery pack. The auxiliary battery pack is on line in parallel with the
main pack. The main battery pack is NiCad while the auxiliary pack is NiMH.
A set of spare AO-40 NiMH batteries was found at the AMSAT lab in Orlando
FL. WA4NFY and W5DID began a series of tests that showed the auxiliary
battery pack should work well if they are otherwise undamaged and if the
main battery pack can be pulled off line.
Thursday, 29-Jan-04: Initial attempts to turn on the K-tx with short machine
code commands did not result in a detectable signal, but this will be
repeated. Several additional cycles with the S2 have been repeated as well
without result. These attempts always terminate with transmitter off
commands, and simple commands to try to switch the battery to the aux. mode.
Our hypothesis remains that we have a battery failure clamping the voltage
low. The BCR is putting significant current into the batteries trying to
get them back to nominal voltage. We only need for one of these cells to
lose enough electrolyte to "open" and we could be back in business. Time is
an unknown here and days or weeks without result do not mean ultimate
failure. The command team will continue to try to regain the S2 and K Tx's
and report any successes.
The AMSAT-NA Board of Directors conducted a teleconference to discuss the
details of the events of the past week. The Board expressed its full
support for the AO-40 command team and appreciation for the detailed timely
information they are providing to the Board and the membership. The Board
also reaffirmed its support for the Eagle and P3E projects that will provide
new high orbit satellite capabilities in the future.
A great deal of technical data on AO-40, including interior construction,
telemetry points and pictures can be found in AMSAT Journal, Volume 23, No.
AO-40, Special Phase 3D Launch Issue -- November 2000. This is available
from the AMSAT office on the AMSAT Journal Set 1995-2000. Call Martha at
(301)589-6062 to order your set.
The preceding data is a summary of detailed reports prepared by Stacy Mills
W4SM (AMSAT VP Operations) supplemented by messages from Peter Guelzow DB2OS
(President, AMSAT-DL), Stan Wood WA4NFY (AMSAT VP Engineering) and Lee
McLamb KU4OS (AMSAT News Service Senior Editor and first alternate on the
AMSAT Board of Directors).
Rick W2GPS
AMSAT Executive VP
[ANS thanks Rick Hambly, W2GPS, for the above information.]
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