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:

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. 😉



Gaia news flash #15

Thruster as used for the CPS of Gaia. (Source: Astrium)

Thruster as used for the CPS of Gaia. The diametre of the nozzle is 3.7 cm (Source: Astrium).

1.) Gaia has successfully finished the second insertion manoeuvre into the L2 orbit. This final insertion burn was executed this afternoon and could be followed based on tweets of @esaoperations, @ESAGaia and @danielscuka. The latter is a very active ESA employee working at the control centre ESOC in Darmstadt ;). For the manoeuvre the spinning of Gaia was stopped. Then the satellite was oriented for the manoeuvre in a way that during the manoeuvre the instrument will never see the sun. Observing the sun with an instrument build to observe stars of magnitude 20 or even fainter would yield heavy damage to the instruments and had to avoided at any time.

For the burn today 5 of the total 8 10N thrusters of the Chemical Propulsion System of Gaia were used. The burn took about 30 minutes and 25 kg of propellant were used. With this burn Gaia has reached its operational orbit around the L2 point. One orbit will take about 180 days. About every 45 days a small manoeuvre will be necessary to avoid that Gaia will drift away into interstellar space. Note, that orbits around L2 are not completely stable, from time to time small adjustment manoeuvres are necessary to keep the desired orbit.

Update 15/01/2014: ESA has published an article with more interesting facts about this manoeuvre at this location:

2.) ESA has published a very neat time-lapse video showing launch preparations for the Gaia mission in Kourou starting with the impressive test of the sunshield deployment and ending with several views from the launch. Very impressive. Enjoy the video here:

3.) A colleague of me working at ESAC near Madrid, Emmanuel Joliet, has a nice blog, and now he is also writing about Gaia. There is a very interesting article posted about his involvement in the mission during recent years and his impressions from the launch. A very nice read – and here it is:

Gaia: After the launch, on the way to L2

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.

The Lagrange points of the     Sun-Earth system with a satellite orbiting the L2 point as Gaia will do.

The Lagrange points of the Sun-Earth system with a satellite orbiting the L2 point as Gaia will do.

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

The control room of Gaia at ESOC, Darmstadt, Germany.

The control room of Gaia at ESOC, Darmstadt, Germany.

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).

The Phased Array Antenna (PAA) can be seen in the center of the service module of Gaia.

  • 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.
The Lagrange point L2 in the Sun-Earth system - also called SEL 2.

The Lagrange point L2 in the Sun-Earth system – also called SEL 2.

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: . 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.

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 #13


Soyuz VS06 is rolling through the mobile gantry on its way to the launch pad.

1.) The Soyuz launcher that will propel Gaia into space was moved to its launch pad at the spaceport in Kourou. The sixth Soyuz to be launched from this space center in South America was leaving the processing building (called MIK) on a special transport vehicle on rails for this trip to the launch pad in about 700 m distance. It passed through the mobile gantry before reaching its final destination (before being launched). At the launch pad the rocket was erected by a hydraulical system located on the mobile transporter. This is an “easy” stretch as the rocket weights only about 25 tons without fuel and without the upper composite consisting of Gaia and Fregat upperstage encapsuled in the fairing. All the access arms to the rocket were put in place before the mobile gantry was moved to enclose the Soyuz rocket. The mobile gantry protects the rocket from the subtropical climate at the spaceport. Please read this blog post for more details at and see the complete series of photos at


The upper composite with Gaia arrives at the launch pad.

2.) Gaia was transported to the launch pad, too. As part of the upper composite, which also is comprided of the fueled Fregat upperstage and the fairing, Gaia was moved by a special transporter from the S3 building to the launch pad in 23 km distance. A crane of the mobile gantry was used to lift the upper composite to the top level in 36m altitude for the connection with the Soyuz launcher inside the gantry. It was bolted with more than 100 bolts to the third of the Soyuz VS06. Gaia has reached its final destination – before leaving Earth! Please see the impressive report with many images at and even more images here

All reports and photo galleries reported about were provided by Isabelle D., the QA engineer of Gaia from EADS-Astrium. Many thanks for keeping us updated. Merci beaucoup!

In the days coming final checks of the launcher and its payload Gaia will be conducted at the launch pad – as usual. Assuming that no serious issues will be discovered everything looks very good for a launch on December 19. Let us keep the fingers crossed!

Update Dec. 16: ESA has bnow published a new blog post summarizing the processing steps during the recent week starting with the mating of Gaia with its Fregat upperstage and ending with installation of Gaia on the launcher. Enjoy the article here:

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.