As you know the Gaia satellite was launched already on December 19, and now is still on the way to its final destination: an orbit around the Lagrange point L2.
So what has happened after the launch? After the separation from the Fregat upperstage an automated sequence started to activate the primary systems of the satellite:
- Switch on of the transponders to enable communication with the ground stations.
- Switching on the gyroscopes for the stabilization of the satellite.
- Releasing the bipod ramps that were supporting the glass-fibre reinforced polymer bipods during the dynamic launch event. The latter will allow a thermal insulation of the payload module from the service module, but were not strong enough to withstand the loads during the launch.
- Pressurizing the Chemical Propulsion System (CPS).
- Activating the thermal control system of the spacecraft to avoid damage to the electronic components.
- Orienting the spacecraft in relation to the Sun to allow the solar panels to be directed towards the Sun.
- Start of the deployment sequence of the sunshield of Gaia by activating the explosive charges in the 12 bolts that were connecting the sunshield elements to the thermal tent (main satellite bus). The successful deployment was confirmed by 14 micro switches.
Everything went smoothly as we could follow at the control center of the Gaia satellite at ESOC, Darmstadt (more information about the launch event at ESOC you can find at https://hvossgaia.wordpress.com/2013/12/21/the-launch-of-gaia-as-followed-from-esoc/).
The commissioning phase for Gaia had begun. Teams from Astrium, ESA and DPAC will prepare the satellite for its nominal mission. This commissioning phase will take more than four months. The following steps were already successfully taken:
- Decontamination of the payload by activating heaters on the optical elements four hours after launch for about 7 days. This should release all gas molecules sticking on the mirrors.
- Activation of the star trackers to allow a more precise pointing of the spacecraft.
- “Day 2” manoeuvre with the CPS to give Gaia a final push towards the targeted L2 orbit.
- Inclining the vertical axis of the satellite 45 degrees away from the Sun. This is the orientation of the satellite that will be used during its observations. This manoeuvre happened on December 20.
- Switch on of the atomic clock and the main memory (PDHU) of the spacecraft (Dec 21).
- Test of the engines of the propulsion system (Dec 21).
- Gaia passes the orbit of the Moon in 388400 km distance from the Earth (Dec 21).
- Testing the Phased Array Antenna (PAA) of Gaia. Note, that this is an antenna that can direct its transmission without using any moving parts. Any movement would disturb the observations of Gaia (Dec 22).
- Test of the Micro Propulsion System (Dec. 22).
- End of the contamination heating. Now the satellite starts to cool down to its operational temperature (Dec. 26).
- On December 30 Gaia has reached a distance of 730000 km from Earth – about half of its way to the L2 orbit. A calibration burn of the thrusters of the CPS is conducted in preparation of the first big insertion manoeuvre into the L2 orbit planned for January 7.
All operations went very smoothly this year. Let us hope it will continue this way next year! All the best for 2014!
Note: The original version of this article you can find in the blog of Isabelle D., the QA engineer of the Gaia spacecraft of EADS Astrium, at: http://reves-d-espace.com/2013/12/31/gaia-apres-le-lancement-en-route-vers-l2/ . Many thanks for allowing me to reblog this in English. Merci beaucoup!
Please follow also @ESAGaia and @esascience on twitter for the latest information about the mission.