The internal temperature
is around 32 deg celsius, decreasing now. Last monday, it was around -20 deg
celsius after having been in total obscurity for more than 24 hours not even
seeing the earth reflection as indicated by the telemetry. The third stage
slowly revolves around itself and spins too. Both effect combine to affect
illumination. In fact, we expected even worse conditions and the temperature
range is within the limits.
The batteries are in good health.
Starting from wednesday-thursday night, the telemetry channels of CU1 are all zero while the processor still keeps on transmitting frames and timing the payload. There are three possible causes in the order of highest to lowest probability :
- thermal crackdown in
the pcb affecting the ADC SPI bus or power supply.
- thermal crackdown in
the ADC chip
- chip destruction by
high energy particule.
- uP port destruction.
When the payload cools down and the pcb shrinks, we'll have a chance to recover the telemetry if the first hypothesis is the right one.
As for the translation of the terms:
OPTRO :each payload is fitted with two light sensors which are basically a BPW21 photodiode behind a 2mm thick PTFE windows giving a cosine response of incident light flux. The photodiode is wired as a photocell loaded by a 5k resistor. Under full sun at AM0, the max voltage is around 150 mV depending on temperature. One the two light sensor is fitted with a LM335Z temperature sensor to allow for correction (TEMP OPTRO channel).
On the pictures, the light sensors are the two brass bolt like extrusions ontop the payload housing (Z+ side). One is besides the X+ side (coax connectors), the other at X- side (arming plug connector). The description of the light sensors is given at http://www.amsat-france.org/satedu/
TEMP BOITIER : case temperature taken at the bottom of the X+ side of the payload. LM335Z sensor.
T ISD : a temp sensor glued on the ISD25120 voice recorder chip. One of the voice message is a 1800 Hz tone recorded at 20 deg celsius. As the internal free running clock of the ISD is temperature dependent, the measure of the received tone frequency gives a very rough estimate of the internal temperature of the payload. < 1800 Hz => < 20 deg, > 1800 Hz => >20 deg .
MOY ORBITE : on
CU2, three channels are monitored for mean, max and min values.
OPTRO1
OPTRO2
TEMP OPTRO
There are two mean values
: a 10 minutes one, which integrates the values of the last ten minutes and
an 90 minutes one. The last one is reset every 90 minutes while the first
one is a sliding mean. That was devised to get some tlm values around the
orbit as it was impossible to have amateur stations continuously monitoring
the sat.
In the decoded tlm channels, you read :
OPTRO1 mean value, 10 and 90 minutes (orbit)
OPTRO1 min value since mean reset and time stamp
OPTRO1 max value since mean reset and time stamp and the same applies to OPTRO2
and OPTRO TEMP.
So we need at least a full super frame ( 5 frames, each with subframes) every 90 minutes.
The instantaneous light sensor value (E subframe on CU2, A and B subframe on CU1) is transmitted during each frame i.e. every 12 seconds on CU1 and every 22 seconds on CU2 to adequately sample the spin rotation.
The place of the other temp sensors is visible in the pictures on the web site.
The voltage of the Li Thyonile batteries is measured after the schottky coupling diodes (400 mV drop).
On CU1, it is measured
during standby, on CU2, it is measured during transmit.
On CU2, the RF power indication is taken from a diode rectifier located near
the PA output coil and the spacing has been adjusted to get roughly 600 mV
at 1.25W ouptut. The indication is temperature dependent and the TX temp sensor
is located just besides the PA which is a BLT50.
...
Hope it gives you some insight of IDEFIX and answers your questions.
Best 73.
Ghislain F1HDD/ON1RG