[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[jamsat-bb:3727] SEDSAT-1: In trouble!
Hi Everyone,
It appears as if two of the primary "experiments" on board SEDSAT-1 are
not
performing to spec (solar panels and batteries), and sometime around orbit 22,
the
spacecraft power cycled. Due to the power cycle, the 89 deployment images were
lost, and due to the low power available, the spacecraft is in a reduced state
of operation.
This lack of telemetry was first noticed by John Melton from AMSAT-UK on
orbits
23-25 and I noticed it in Tucson on orbit 26 at 7:23 UTC 10/26. On orbit 27,
in
Tucson, we heard 5 telemetry bursts, spaced at 1 minute apart, and we captured
and
decoded 3 of them, indicating that the spacecraft had gone to zero power and
cycled. The satellite went quiet again about half way through the 16 minute
pass,
and was quiet on orbit 28, indicating that it had gone into its "power cycle"
mode, whereby it notices that it is in extremely low power conditions, and
waits
10 hours until attempting to transmit again.
It was evident from the orbit 13-16 telemetry that the spacecraft was in
a "power
negative" situation, but even under the worst power generation circumstances,
the
satellite should not have cycled as early as it did (nearly twice as fact as
expected), which indicates that the batteries are not storing their specified 8
A-h, and are likely somewhere around half that capacity.
The solar panels are producing about as much power expected, but are
slow to
react when exiting an eclipse period, so charging of the batteries doesn't
occur
until at least 10 minutes into a daytime cycle.
Anyway, I don't have too much time to explain more, but let me say that
we need
your help. We need to get as much as the little data that the spacecraft is
transmitting, in as many conditions as possible. The only decoded data we have
right now is for Tucson, and these are for periods that the spacecraft has just
left eclipse or is still in eclipse. We need more data for the periods around
when the spacecraft is nearing the end of its day cycle, and entering eclipse.
(I
believe there's a reader in New Zealand that can observe these conditions).
All
you need to be able to do is receive 437.91 Mhz 9600 baud FSK (adjusting for
doppler), and run our telemetry program which is now at the SEDSAT site at
http://www.seds.org/sedsat/tracking
The software is a simple program written by Chris Bond of UAH, which
decodes the
telemetry from the TNC, displays it to screen, and writes it to file with the
local time received. To use it you must put your TNC in KISS mode, and must
set
the appropriate COM port parameters. For those who do use it and hear and log
telemetry, please email the telemetry, the orbit #, your lat/lon, UTC offset,
and
a brief description of your hardware (for fun) to telemetry@seds.org. We're
sorry
that this software wasn't out earlier, but its urgency wasn't realized.
Since the spacecraft was being observed last time it power cycled, the
next time
it should be talking again will likely be after 19:00 UTC 10/26. If it
continues
to operate in a similar fashion, the satellite may reset every 10-11 hours, but
we
have yet to figure that out.
Current two-line elements are also available at the SEDSAT web site.
Its disappointing that the deployment images were lost, but its too early to
give
up on the rest of the satellite, so lets see if we can figure this out
together!
For those curious, but unable to receive, here are what the last three packets
from SEDSAT looked like:
The "Amps In Batteries" number is the critical one here. Peak capacity is
theoretically around 28 million, and it should usually be above 20 million, but
you can see here that we are way down at 1.2 million. Since the spacecraft
did
reset, however, the number quoted for this value should be accurate regardless
of
the actual capacity of the batteries.
10/26/1998 2:9:6 Main Voltage: 20185mV Main Current: 722mA Amps In
Batteries:
1233332mAS
Battery 1: 5 Battery 2 : 7 CDS DC/DC : 17 MODE-L DC/DC: 23 EMP: 6
MB DC/DC : 4 Deployer 1: -5 Deployer 2: 8 MODE-L PA : 7
+X: 0 +Y: 0 +Z: 0 -X: 0 -Y: 0
SEASIS BOOT: 3 CDS Boot: 1 Reset Count: 0 Images Available: 0
Mode-L: 1 Mode-A: 0 SEASIS: 0 Cameras: 0 Antennae Deployer: 0
Panel: 0
10/26/1998 2:10:6 Main Voltage: 20185mV Main Current: 728mA Amps In
Batteries
: 1211532mAS
Battery 1: 5 Battery 2 : 6 CDS DC/DC : 17 MODE-L DC/DC: 23 EMP: 3
MB DC/DC : 3 Deployer 1: -6 Deployer 2: 6 MODE-L PA : 5
+X: 0 +Y: 0 +Z: 0 -X: 0 -Y: 0
SEASIS BOOT: 3 CDS Boot: 1 Reset Count: 0 Images Available: 0
Mode-L: 1 Mode-A: 0 SEASIS: 0 Cameras: 0 Antennae Deployer: 0
Panel: 0
10/26/1998 2:11:6 Main Voltage: 20185mV Main Current: 726mA Amps In
Batteries
: 1189736mAS
Battery 1: 4 Battery 2 : 6 CDS DC/DC : 16 MODE-L DC/DC: 22 EMP: 4
MB DC/DC : 3 Deployer 1: -6 Deployer 2: 6 MODE-L PA : 5
+X: 0 +Y: 0 +Z: 0 -X: 0 -Y: 0
SEASIS BOOT: 3 CDS Boot: 1 Reset Count: 0 Images Available: 0
Mode-L: 1 Mode-A: 0 SEASIS: 0 Cameras: 0 Antennae Deployer: 0
Panel: 0
--
------------------------------------------------------------------------------
Christopher A. Lewicki KC7NYV 520.977.0758 Maintainer of SEDS.LPL.Arizona.EDU
Project Manager, University of Arizona Student Satellite Project
----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org