11/2010: The Odin satellite observes water in comet 103P/Hartley 2
Comet Hartley 2 orbits the Sun with a period of 6.5 years. This year, it passed closest to the Sun on 28 October at distance of 1.059 AU (Astronomical Unit = Sun-Earth distance = 150 million km) and on 20 October, it was only 0.121 AU from Earth. An international team, with astronomers from the Paris Observatory, took this opportunity to observe the fundamental line of water at 557 GHz with the Odin satellite. The comet produces 180 to 300 kg of water per second, and this production varies in time, certainly in phase with the rotation of the comet's nucleus.
Read the full article
02/2005: 4th anniversary of ODIN satellite launch
You can see some of the scientific results obtained in aeronomy and in astronomy. You can also see publications about these two themes.
A press release marked this fourth anniversary of the satellite's launch.
ODIN First Scientific Results
03/2002: 38th Odin Science Team Meeting and Odin inter-agency Meeting
Beginning 2002: Scientific programme kick off
02/2001: First AOS spectrum in orbit.
Here's the first spectrum obtained with the AOS instrument which shows the H2O spectra in Earth's atmosphere.
This is not a "scientific" spectrum, however as the telescope was pointing roughly in the direction of Earth's atmosphere and the amplitude measurement ("(ON-OFF)/OFF" ratio) has no real significance. The frequency calibration is also incomplete, because orbital information is lacking.
Thus the spectrum shows that everything is working very well, with a very clean base-line. The AOS is operating in excellent environmental conditions and the temperature regulation is good. The internal calibrations (frequency comb) show that the optical alignment is nominal.
Note that the rest of the radiometer is also working as planned and that the satellite should provide very-high-quality aeronomy and astronomy measurements.
02/23-02/28/2001: Information from Olivier VandermarcqInstrument
- Autocorrelator (1 et 2): powered up 23/02
- Radiometer: powered up 26/02, 27/02
- 1st signals recorded using 2 configurations corresponding to a typical aeronomy case and a typical astronomy case (but without the cooler and without OSIRIS)
- AOS: powered up 27/02
- Cryostat: powered up 24/02 to get an evaluation of the perturbation level before it is unclamped.
- Chopper: tested
- The telescope was unclamped on 23/02 and the perturbation was measured by the gyros, allowing us to conclude that the pyros worked.
Attitude control system
- ACDC 1/2 (Attitude Control Determination Computer): checking of onboard orbit propagator quality
- Gyros (Regys 3S Sagem):
- Gyros 1, 2, 3 powered up 22/02
- Gyro 3 (backup gyro) turned off 25/02 after health checking
- Spinning top power (IVT): sampled for each visibility: steady as expected before flight
- Temperatures: steady
- Meca: GP1 ~60°C, GP2~55°C, GP3 ~50°C
- Elec: GP1,2,3 ~45°C - Drift: no figures really reliable for the moment, taking into account that the star trackers are not being used for the moment, there are no good alignments between sensors and there are angular speed variations.
- Checksum: measured on GP1: OK - Star Trackers (Sed12 Odin)
- ST2 powered up 25/02: OK
- calibration parameters uploaded
- power consumption OK
- Solar sensors acquisition (BASS Astrium)
- CS3 is pointing in the direction of the Sun: exit level OK taking into account seasonal effects.
- misalignment of about 0.15 degrees between the 2 sensors
- Magnetometers (SSC): OK
- Wheels (ITHACO)
- temperatures a little low (a few degrees above the acceptable level for wheel 3)
- equipment used: 3 wheels, solar sensors, 3-axis magnetometer
- observation of the exchange of kinetic momentum between X/Y wheels
- analysis over several days of wheel speed variations and behaviour of wheel speed desaturation function
- pointing / steadiness
- equipment configuration changes (mecanisms, Tx antenna, instrument) are visible on magnetometer measurements (explanation of differences up to a few degrees).
- Atlantic South Anomaly visible on magnetometer measurements
- angular speed steadiness of about 1 to 2 10-2 °/seconds on each axis
- Standby Magnetic
- this mode was activated for 3 minutes during a visibility window, then the satellite was switched back to Safe mode
- equipment used : 3 wheels, solar sensors, 3-axis magnetometer, 2 gyrometers + orbit models, magnetic field, Sun direction
- inertial pointing: the attitude variation was limited for Safe => Standby transition
- angular steadiness: evaluated to be 10 times better than in Safe mode (by Soda: CNES attitude restitution software)
However: a 0.01 deg/second bias around the Sun direction instead of the inertial pointing expected
- Transition Safe/Standby Anomaly
- On the return transition, the ACS switched to detumble mode before Safe mode; this unexpected anomaly is being analysed at SSC and Saab Ericsson Space.
Miscellaneous platform items
- Mass memory
- 1 bit error occurred several times.
- GPS memory (Rockwell)
- Acquisition works but switches off frequently
- Communications: OK
- Alimentation: OK
- Batteries, Solar arrays: OK
- Odin System Unit: OK
- Thermal control: OK
Control Centre (Kiruna)
Tuning of ground/onboard (TM/TC) procedures.
N.B.: A software tool provides attitude sensor telemetry to an attitude control system simulation (flight software). This enables analysis (off-line) of the attitude control software's behaviour (visibility upon the internal parameters) when all the telemetry is available (especially for each visibility window but also on specific recordings by the mass memory).
CNES' attitude restitution software (Soda) was adapted to perform restitutions from the star tracker, magnetometers and gyro telemetry.
TM/TC Ground Station
CNES 2-GHz ground station was tested to provide a redundancy.
Two weeks for outgassing before cryostat unclamping and switch-on, cooling for several days before reaching working temperature, then pointing out in the direction of Jupiter for a first calibration.
After analysis (and anomaly correction) of the Stanby/Safe transition:
- Switch to Standby Magnetic mode
- Star Tracker tests
- Switch to Standby Celestial mode
- Rough Star Tracker calibration
- Switch to Aeronomy/Astronomy modes
02/20/2001: 1st day in orbit, news from Olivier Vandermarcq
1st pass (the 20/02/2001 at 9h04)
The first pass within view of the Esrange station didn't allow communication to be established with the satellite, even if a signal was received indicating that some commands were been executed and that the separation took place.
The satellite was for this first pass exactly in the direction expected.
No surprises for this first pass because the configuration wasn't favourable (Solar arrays folded up, satellite very low above the horizon). The synchronization word allowing the satellite telemetry to be decoded couldn't be retrieved (signal too low). There was no received signal that could have allowed part of the telemetry to be retrieved off-line.
2nd pass (the 20/02/2001 at 10h36)
During the second pass, the satellite telemetry was immediately decoded showing that:
- the satellite was in "safe - PID control" mode
- the solar sensors were showing a pointing at a few tenths of degree from the Sun
- the four solar array panels were unfolded
- the satellite (electrical power supply, temperatures, communications) was functioning nominally
There was a huge sense of relief at the Kiruna Control Centre.
The telemetry showed reaction wheel speed increasing quicker than expected.
The decision was taken to trigger the wheel desaturation function during the next pass. This could be achieved by sending a command to the ACDC (Attitude Control Determination Computer) to decrease the wheel angular speed threshold that triggers the desaturation mode.
This command was tested on an ACDC simulator then telecommand procedures were defined.
After a general status and attitude check, the threshold change telecommand was uploaded to the satellite and the wheels' absolute speed decrease could be checked in real time. New commands were then uploaded to restore the wheel speed threshold to nominal values.
The following pass enabled the testing of:
- the GPS receivers (one out of two working)
- the CNES TM/TC ground station (for back-up operation)
- the mass memory and platform housekeeping data recording working through out orbits
- the ACDC 2 (the satellite attitude staying under ACDC 1 control)
- and the supply of reaction wheel number 4 (back-up)
All is nominal until now, even though perhaps some temperatures are a little higher than expected (this is better for the reaction wheels). The satellite is in Safe mode for the moment.
The orbit data were retrieved on the evening of the 20th and access to them was given to PDC Centre users. Orbit data retrieval processing is working well.
The satellite was placed into its operating orbit, with a very good accuracy.
Before the end of the week, the gyrometers will be started up and tested.
02/20/2001, 8h48: Successful ODIN satellite launch.
The ODIN satellite was successfully launched from Svobodny by a START-1 launcher on 20 February 2001 at 8:48.
About 16 minutes into flight, the satellite was put into orbit and the Esrange station received the first messages from the on board transmitter.
The second pass over the Esrange station took place between 10:35 and 10:45 UT and a contact with the satellite was set up from the AOS. The solar panels were unfolded, the satellite was pointed in the Sun direction and the batteries were OK. The ground/on board link and attitude control system are working well.