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: .

Even more details are available here: .


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: & .

News will also be posted on Facebook at: .

The team I am part of will also update you on Twitter as @GaiaUB and on Facebook: .

And not to forget there are such old school things like this website from ESA  and from our GaiaUB team: .  😉

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.