… One-year anniversary of the launch of Gaia …

On December 19, 2013 the Gaia mission was successfully launched. For the first anniversary of the launch I had prepared a small tribute video. Finally I have found the time to post it here. You can guess what it is about … yes – it is about a scale model launch: The 1:50 Soyuz-Fregat was launched – this time with five motors instead of one:

Impressed? More about this kind of scale model rockets you can find here:

https://hvossgaia.wordpress.com/scale-model-rocketry/ .

Gaia commissioning was successfully finished – and routine observations have started

Yes, finally we can spread the news: The In-Orbit Commissioning Review (IOCR) for Gaia was successfully concluded on July 18. The ESA Gaia project team handed over the responsibility for the satellite to the Gaia mission team under the leadership of Wil O’Mullane, the new Gaia Mission Manager.

Handover of the Gaia flag to the Gaia mission manager

Handover of the Gaia flag to the Gaia mission manager

Now, 11 days later this news has been published by ESA. That was not very fast – we agree on that. But notice that ESA is very busy with the Rosetta mission going into the most interesting phase now, the final ATV will be launched soon and many things more. And we have an astronaut on-board the ISS. And do not forget that we have the holiday season already. To organize this publication was really complicated. 😉

Gaia has  started the normal operations already last Friday and will now observe the sky for 28 days in the so-called Ecliptic Pole Scanning Law (EPSL). This scanning law allows to observe a high number of stars near the Ecliptic poles very often to allow an initial photometric calibration of the instrument.

For more details please see this release of ESA:

http://www.esa.int/Our_Activities/Space_Science/Gaia/Gaia_Go_for_science .

Even more details are available here:

http://www.cosmos.esa.int/web/gaia/news_20140729 .


Personal note:

In the operational phase the news about the Gaia mission will be rare. Thus, please do not expect many publications here until the release of the first catalogue with Gaia data expected for the summer of 2016.

In the meantime ESA will publish all news about the progress of the mission via their Twitter accounts:

https://twitter.com/ESAGaia & https://twitter.com/esascience .

News will also be posted on Facebook at: https://www.facebook.com/ESAGaiaMission .

The team I am part of will also update you on Twitter as @GaiaUB and on Facebook: http://www.facebook.com/GaiaUB .

And not to forget there are such old school things like this website from ESA http://www.cosmos.esa.int/web/gaia  and from our GaiaUB team: http://gaia.am.ub.edu/ .  😉

In this blog I will continue to post more about my non-Gaia activities . You see the topics listed at the left side of this page. Feel free to open one or the other topic and you will be surprised. 😉





Gaia – before starting the normal scientific observations


Final preparations are underway to start the normal routine scientific observations of Gaia. Part of the final preparations to start the normal operations was a mild heating of some of the mirrors of Gaia to remove a very thin layer of ice particles on June 30. Now the mirrors have to cool down again until thermal equilibrium is reached. An update of the on-board software was successfully performed. The focus for both telescopes over the entire focal plane will be checked again. Some parameters for detection of sources on-board will be optimized, too. This includes parameters for activating shorter observations for the stars brighter than magnitude 13 to avoid that the corresponding images will saturate. We call this “observations with “activated gates”. How does this work?

There are different “gates” with different effective exposure times available ranging from 0.01 seconds to 4.3 seconds to cover a huge magnitude (brightness) range that can be observed. These “gates” will be activated depending on the magnitude of the stars determined on-board the satellite by the star mapper (SM) CCDs which will “see” the stars first. A few seconds after these observations with the SM CCDs the same detected source will be observed by 11 more CCDs in the same row of the SM CCD that has detected this source. If the star is detected as bright then the “gates” will be activated to avoid the saturation of the images. Saturation depends on many factors such as the colour of the star, the scan motion of the satellite, the point spread function (how the image of a stars looks like) and even how the image centre is located in intra-pixel space.

Parameters for the activation of the short gate 4 computed in a test for all AF CCDs.

Parameters for the activation of the short gate 4 computed in a test for all AF CCDs.

We have updated our knowledge about these characteristics of the observations based on data collected during the commissioning phase and in this moment new parameters for the activation of the gates are computed. Almost 1 billion of 2D images are simulated for this purpose at this moment to be able to find the perfect parameters. Parameters are computed for all 55 AF (astrometric white light) CCDs, all BP (blue photometer) CCDs and all RP (red photometer) CCDs. More than 7000 parameters are determined and need to be uploaded to the satellite before Gaia will start the normal scientific observatons. By the way, the corresponding LUT (Look Up Table) is  the biggest parameter table used on-board Gaia.

More details about this topic can be found in an earlier entry in the ESA Gaia blog following this link.

And now, after this very work intensive commissioning phase we are really looking forward to start the normal operational phase of our very interesting Gaia satellite mission to create the world biggest, multi-dimensional map of about one billion stars and other light sources in our galaxy and beyond.


Summary of Gaia news during recent days

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:

http://blogs.esa.int/gaia/2014/06/16/preliminary-analysis-of-stray-light-impact-and-strategies/ .


Gaia news flash #17: How stars are detected and some additional information about the commissioning status


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.  😉

Much more details about this topic can be found in the ESA blog entry:  http://blogs.esa.int/gaia/2014/04/03/detecting-sources/.

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. 😉


Is this Gaia?


The Gaia spacecraft as seen today as a mag 15 object – after changing again the Sun aspect angle of the satellite to 0 deg earlier today – during the first hour of observations with the TFRM telescope at the Observatori Astronòmic del Montsec (OAdM) in Catalonia. A second telescope, the Telescopi Joan Oró (TJO), is observing Gaia, too. Photometric time series are taken for several hours.

Gaia news flash #16

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:

http://www.cosmos.esa.int/web/gaia/iow_20140214 .


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:

http://www.sterne-und-weltraum.de/news/den-himmelsvermesser-gaia-plagen-kleine-pannen/1224160 .

  • 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.