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.


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.

Short update about the Gaia commissioning

Image of cluster NGC 1818 taken by the Gaia satellite. (Source: ESA)

Image of cluster NGC1818 taken by the Gaia satellite. (Source: ESA)

ESA has published an update about the status of the commissioning phase for the Gaia satellite. The iterative process of the optimization of the spin rate, the alignment of the telescope mirrors and the focusing is ongoing. The calibration of the different instruments will also continue for a few more months. As part of the early calibration an (for Gaia) unusual operation mode was conducted by taking full images with the SM (Sky Mapper) CCDs. One of these images was published with the ESA article. It shows the star cluster NGC1818 in the Large Magellanic Cloud. Enjoy the article and the image at

A personal note: Sorry for not posting more often. This has two reasons: 1.) We are very busy with the commissioning work and its challenges, and 2.) We have to follow some rules for publishing info set by the Gaia Data Processing and Analysis Consortium (DPAC) and ESA.

Expect more news next week.

A recommendation: Follow @ESAGaia and @ESAScience on Twitter – there are almost daily updates available.

The launch of Gaia – as followed from ESOC


Our group from the GaiaUB team with the 1:4 Gaia model at the ESOC launch event in Darmstadt, Germany.

A group of four scientists from the Gaia team of the Universitat de Barcelona (short GaiaUB) followed the invitation of ESA to watch the launch of the Gaia spacecraft from the European Space Operations Centre (ESOC) in Darmstadt, Germany. It was a real pleasure to share this event with many other scientists, engineers and journalists from all over Europe. The event started about one our before the launch. The ex-astronaut Thomas Reiter, now ESA Director of Human Spaceflight and Operations, was the first speaker welcoming the audience and giving an overview of the Gaia mission as one important part of the general ESA stategy to support science and development of new technologies. Mark McCaughrean from ESA was giving an enthusiastic talk about the working principle of Gaia and the science that can be done with the data expected to begin to arrive in the next few weeks. The general director of ESA, Jean-Jacques Dordain, was giving a short statement from ESA headquarters in Paris via telecon. Finally, Jean Dauphin from EADS Astrium outlined that it was a pleasure and a challenge to build the Gaia spacecraft.


Moment of liftoff of the Soyuz-Fregat carrying Gaia into orbit as seen at the ESOC launch event

Then, the launch transmission from Kourou, produced by Arianespace, was beginning. Most likely you have seen the videos already. If not, here is the full transmission: or the short highlight version: We were following step by step of the launch sequence. You could real feel the tension of the entire audience in the air. What a beautiful launch – the most impressive one of a Soyuz from Kourou so far! After several days with rain in Kourou a large gap had opened in the clouds allowing the follow the liftoff even after booster separation!


Nic Walton of the IoA Cambridge during his enthusiastic performance at the ESOC stage. What a passion!

During the coast phase and the second long burn of the engine of the Fregat upperstage some scientists involved in the mission were expressing their excitement about the launch and the mission at the ESOC stage, among them Sergei Klioner from the Dresden university, Nic Walton from the IoA Cambridge and Uli Bastian from the ARI Heidelberg.

Finally, the successful separation of Gaia from the Fregat upperstage was confirmed from the control room in the building nearby as well as the first radio contact with the satellite after launch. An intensive applause started and you could feel the tension to go down. Gaia was on its way to L2, almost.


Successful deployment of the sunshield confirmed as seen on the monitors of ESOC

Some critical operations needed to be performed first including the deployment of the 11m diameter sunshield. We could watch on monitors the work going on in the control room. About 1.5 hours after liftoff it was announced that the sunshield was opened successfully – Mission ON! What a relief for everybody! Now the celebration was really beginning with champagne and a buffet.


Look into the mission control room of the Gaia spacecraft at ESOC a few hours after launch

Later on we had the luck to be able to have a look into the mission control room of the Gaia mission. This was another emotional moment knowing that Gaia will be operated from here during the years of operations to come. Many thanks to the person allowing this close look not completely in agreement with the rules set.

I have to express my thankfulness for being allowed to take part in this fantastic event! This is something I will always remember. Thanks to ESA, Arianespace, Astrium and CNES to make this dream come true after all these years of hard work. And many thanks to our Russian friends providing this fantastic Soyuz-Fregat launcher. We have to be thankful to all persons that were helping to make this launcher to work properly, from the last person how touched the Soyuz and back to the person who has constructed the basic version of this launcher in the 1950s – Sergei Korolev. Thank you, merci beaucoup, spasibo!

Update: A series of photos from this event is now available here: You will need to be logged in into Facebook to see it. Sorry for this issue!

Update 07/01/2014: The entire launch event at ESOC can now be watched on YouTube at:

Gaia news flash #12: Christmas present for astronomers is wrapped up!


Payload fairing that will be used for the launch Gaia.

1.) We just got the news by a tweet of @ESAGaia that both halfs of the fairing were put around the Gaia spacecraft and the Fregat upperstage. This package is ready to be launched on December 19 and to be unpacked in space as an early Christmas present for the astronomers. Only the delivery service in form of a Soyuz rocket has to be prepared now. The package with the present needs to be picked up and on December 19, 10:12:19 CET we can finally light the Soyuz candle lifting Gaia to the L2 heaven. Great times! 

Update Dec. 13: First images of the Christmas package for the astronomers were published by ESA at: Here they are:

Gaia sitting atop of the Fregat upperstage

Gaia sitting atop of the Fregat upperstage with half of the fairing installed

Now the fairing is closed and the Gaia launch logo is glued to the fairing. What a nice package! To be openend on December 19.


During the process of mating Gaia to the Fregat upperstage.

2.) Reports about connecting Gaia to the Fregat upperstage are now available from Arianespace at: and in the blog of Isabelle D., the Gaia QA engineer of Astrium, at: Before both elements could be mated an adapter had to be installed on Gaia. This is described in the latest ESA Gaia blog post and includes many images. Author of this post is again Isabelle!

3.) ESA has published a new video describing how the Gaia observatory will work by comparing it with examples everybody knows from the real life. Very easy to understand! Here you can find this video:

4.) EADS-Astrium has published a nice infosheet about the Gaia mission on their twitter account @EADSgroup. Here it is:Image

Exciting times for all involved – also for us scientists and engineers. Do you want to get some insight how we are feeling in these days? Here you can find one answer:

Launch fever anyone? ;)


T-7 days and counting. At the Universitat de Barcelona  we have countdown clocks almost everywhere. And these are counting down, second by second, minute by minute, hour by hour. It is getting really serious now with the launch of Gaia. Every single progress statement from the European spaceport Kourou, official or unofficial, is awaited eagerly. The news are distributed with twitter, Facebook, emails, …. People are talking about it on the floors. You can feel the excitement rising day by day.

Many of us have spent several years already working for the Gaia satellite project. A few colleagues were already contributing to the very first studies for a successor of the Hipparcos satellite in the mid-90s. A few days ago I had my seventh anniversary working for the project. Now in a few days the Gaia will be launch and the real space mission will start. Exciting times.

Many of my colleagues are now interested in all aspects about the launch. Questions are f.e. how safe the launcher is or if it is not too early to drop the payload fairing a little bit more than three minutes after the lift off. I am a little bit of an “expert” for these kind of questions. As a kid I was growing up with the first missions of the Space Shuttle. I followed every mission even during the night by radio – AFN (American Forces Network) was distributing the information all over in Germany. Interesting stories were told – orbiting satellites or retrieving them, untethered spacewalks, the Spacelab science missions. It seemed to be very realistic as a mixture of many successes and small failures were reported. Then the big failure happened – the Challenger disaster. A few months later there was Chernobyl. During these months I lost my believe that technology alone can make really everything possible. Before these events I was undecided if I want to considering a career as engineer or as a scientist. The events helped me to decide to study physics. With the overdose of the classic Star Trek taken during my early childhood the main direction of my study was also clear – it had to be Astrophysics. Oops, it seems to be I am a bit off topic here – sorry for that.


After the launch of the final Space Shuttle mission STS-135 at the Kennedy Space Center.

I continued to follow all the Shuttle missions and other spaceflight events. I have watched several hundreds of space launches on TV, and one live – the final launch of the Space Shuttle on the STS-135 in July 2011 from the Kennedy Space Center. A dream was coming true.

As a “space geek” with “my launch experience” I am still calm at the moment. But I think that this will change in the coming days. It really should change! Working several years for a satellite project ties the connection with it a bit more than usual I think. Probably when the countdown clocks will show only a few hours left the launch fever will have infected me, too. 😉 Exciting times, indeed.

Final practice run before the important Gaia Soyuz-Fregat launch


As you know there will one important launch later this year – the launch of Gaia by a Soyuz-Fregat rocket from the European spaceport in Kourou, planned for December 19. For us there will be another important rocket launch a few days later – on December 23. Assuming that the weather cooperates a Soyuz-Fregat model will be launched just a few minutes before the premiere of the new planterium show “Journey to a billion suns”. This movie is dedicated to the Gaia mission and will take you through time and history, explain basic technologies of star mapping. It will take you on a fascinating journey along the numerous features of our Milky Way. The premiere of the show will be held at the planetarium of the Centre d’ Observació de l’ Univers (COU) near Ager in Catalonia with several guests from science and politics. Normally I would do this launch but unfortunately I will not be able to attend.

But we found a very good solution. As you may know we had a few launches with the Gaia Universitat de Barcelona (UB) including a live transmission of launches. Thus, some members of the team have already some experience with these kind of stuff. The most experienced one, Josep Manel, volunteered to perform this important model launch at the show premiere. We decided to practice a bit, and as the weather was perfect last weekend, Josep Manel did perform a real Soyuz-Fregat model launch:

Everything went very smoothly, no issues at all. It was a nice family event under a picture-perfect blue sky.

By the way, this was our first launch of a Soyuz-Fregat model showing the Gaia launch fairing. The design of the logo was just published one week ago by ESA. Lucky me that I did not had to perform the launch. Being a little bit superstitious I promised to myself not to perform a launch with model showing the Gaia logo before the real launch of Gaia. I kept my promise. 😉

More about these model rocket activities you can find in this section: