Sorry for not posting more about the Gaia mission during recent weeks. I just did not find the time for it as there was and is still is a lot of work to be done during the process of commissioning and performance verification for all persons involved. To give a more or less complete overview about things related to the Gaia mission here on this site I would like to summarize the latest news here and now. Here we go:
1.) A sky map/movie was released showing all the regions in the sky already scanned by Gaia during the recent five months. This movie was produced by the @GaiaUB team (with a small involvement from me ;)) and published jointly by ESA, DPAC and Airbus DS – as all publications made during the joint commissioning phase. If you have not seen it yet here it is:
2.) First spectroscopic observations of Gaia were published. The @GaiaUB team contributed also to this publication. You can find it here at the ESA Gaia blog:
3.) And finally, there is a new blog entry in the ESA Gaia blog giving an official, very up-to-date status update, discussing issue like stray light, contamination and variations of the basic angle (the angle between both telescopes of Gaia) and their influences on the scientific measurements. Please read the blog entry here:
ESA has published today some very interesting information how stars are actually detected by Gaia. This is done with the help of 14 Sky Mapper (SM) CCDs. A real SM CCD image (please see above) was published showing the image with and without detection markers. Feel free to find some undetected stars, but please do not mix them with hits by cosmic rays. 😉
There is also some additional information given about the current commissioning activities. We are still working on the issue of unexpected stray light levels. Several manoeuvres of Gaia with different orientations towards the Sun were performed to identify the source(s) of the stray light observed. Significantly progress was made in understanding the situation. The analysis of the data collected by Gaia and from the ground is still ongoing by the teams of ESA, Airbus DS and our DPAC.
Another issue mentioned is that there are indications of some contamination of the payload, presumably by water ice. The water may have entered the payload module during the final launch preparations in Kourou as it was raining at the spaceport at this time – despite the fact that Gaia was under air-condition almost all the time. Several parts of the payload were heated to get rid of the remaining water. Now the payload has to cool down again to operational temperatures. Nevertheless, data is already taken to start to analyse if still some water ice is present within the thermal tent enclosing the payload. The entire process will take a few more weeks to be finished.
Complex space missions are not easy – otherwise someone else would have done a mission like this already. We are doing our best and are working hard to bring Gaia in the best condition possible for the normal operations. We are on a good way I think. 😉
1.) New images taken by the Gaia SM (Sky Mapper) CCDs were just published by ESA. There are images of the cluster NGC 2516, the spiral galaxy Messier 94 and Cat’s Eye Nebula available. Enjoy the new images here:
The spiral galaxy M94 as seen by two SM CCDs. You can clearly recognize the gap between the two CCD chips. Most likely this is the last time that images of these kind of extended objects are downloaded, as Gaia will observe only point sources during nominal observations.
2.) There are some more news about the status of Gaia available now in an article by my colleague Stefan Jordan in the German journal ‘Sterne und Weltraum’. The commissioning is ongoing quite well and will continue until May at least.
Two issues are mentioned for the first time (I think) in this article:
There was a problem with one thruster of the MPS, the Micro Propulsion System. It was delivering much more thrust than desired. But the issue was solved very quickly by a recalibration of the nitrogen supply mechanism.
A contamination issue was detected for one of the mirrors reducing the throughput of the affected telescope by more than the half. The contaminant has still to be determined, but the contamination was already successfully cleaned by heating this particular mirror. Investigations are ongoing to identify the contaminant to make sure that a similar scenario cannot happen again. It is not ruled out that there is a correlation to the stray light issue (more information about this here https://hvossgaia.wordpress.com/2014/02/12/gaia-status-update-after-one-month-of-commissioning/). Parts of the thermal tent are most likely heated by the stray light and an increased outgassing of the paint used for the thermal tent could be an explanation for the contamination seen. But other scenarios are still under investigation. Most likely we will learn more about the issue after next Monday, when the sun aspect angle of Gaia is changed by three degrees to reduce the stray light effect. Let us keep the fingers crossed that this manoeuvre will yield the desired results. 😉
All these are small issues normal for the initial phase of a space mission. In Germany we call it ‘Kinderkrankheiten’ – these kind of not so serious illnesses that small children are suffering from. Solutions were found and in most cases already applied. Overall, the mission progress is quite impressive.