Author Archives: Guest Blogger

Installation on the launch adapter

Following the filling of the tanks, the Gaia satellite enters the Combined Operations Phase: the “COP”. This involves all the different stages by which the satellite is put on to the launcher, the launcher is put on the launch pad, and the launch itself. All of the activities on the satellite are carried out at this time according to a schedule established by Arianespace, who also manage all of the active participants of this combined phase: Astrium as the prime contractors of the satellite, Roscosmos for the Russian launcher, RUAG for the payload adapter and the clamp band, Arianespace or its subcontractors for the electrical testing of the launcher, and CNES for...

Gaia ready for fuelling

Towards the end of November, the first part of the Gaia launch preparation was complete: the satellite was 90% ready, with its tanks pressurised. The second part begins with filling the tanks with the appropriate propellants. This phase is particularly dangerous because the propellants are toxic, and there is also a risk of explosion, so it is carried out in a dedicated building. That’s why Gaia had to move from building S1B in the payload preparation complex (EPCU), where it has been since the start of the campaign, to the S5 building to be fuelled. How do you move Gaia from one building to another? Gaia, complete with its sunshield, could not...

Enter GBOT

We should all know by now that Gaia is destined to study the motions and locations of 1 billion stars, but did you know that in order to achieve this goal, the precise location of the spacecraft itself is needed to an extremely high precision? In addition to the expert tracking methods utilised by ESA’s mission operations team at ESOC, ground- based observatories also provide important data. Enter GBOT, the Ground Based Orbit Tracking campaign that utilises a network of small-to-medium telescopes aiming at doing just that. In fact, GBOT is committed to deliver one set of data per day, which allows the determination of Gaia’s position good to 20 milli arcseconds. GBOT’s...

Stories of the stars

Gaia, the billion star surveyor. This is the mission slogan. A billion stars. One thousand million stars… That is a lot. Really a lot of stars. If the final catalogue with just the summary of all data accumulated by Gaia were printed and all volumes were nicely aligned in my bookshelf, the row of 53,542 volumes would extend 1.3 km (and this would only be the summary data of all non-special stars). So, I hope you appreciate the point that a billion stars is really a lot. This is also what one of the space enthusiasts that visited the open day of the European Space Research and Technology Centre (ESTEC) a few...

Gaia lift-off time

Launching a satellite seems fairly simple: put it onto a rocket and launch it into space. Of course it’s a bit more complicated than this and some missions are more complex than others. In the case of Gaia we have to launch at a very specific time each day. This lift-off time is determined by the Libration Point Mission Analysis Group of ESOC. In this blog entry I’ll explain why this launch time is so constrained and how we determine the exact lift-off time. There are three major factors that contribute to this launch: – The destination of Gaia, the Sun-Earth libration point, or Lagrange point 2 – The programming of the...

On the edge of the possible

It is probably hard to overestimate the effort required to coordinate the Gaia hardware and software development. While the industrial consortium EADS-Astrium developed the actual satellite and onboard software, the Data Processing and Analysis Consortium (DPAC) is responsible for the scientific data processing. As explained in an earlier blog entry, DPAC consists of several hundred people in dozens of scientific institutes spread all over Europe. Because the scientific requirements of the Gaia measurements are on the edge of what seems physically possible, every aspect of the hardware must be understood and calibrated to an unprecedented level – I will give an example below. This has led to a constant exchange between scientists...

Trip of a lifetime: Young ESA’s visit to Kourou

Ever flew over Kourou? Ever climbed a palm tree? Ever slept in a hammock in the jungle? Ever been to paradise with the devil around the corner? We, some of the Young ESA members, were the lucky ones who actually experienced it all in French Guiana two weeks ago. It was possible thanks to the perfect organization of Juan de Dalmau who guided us for a week through the culture, nature and spaceport – and yes, it was great fun! We had the chance to learn about the culture in French Guiana as well as taste the rainforest life! During the first days we visited Cayenne and its traditional market, spent some...

Opening (activating) the gates of Gaia

As you may know already from previous blog entries Gaia will fly the biggest camera ever into space. The image created by the two telescopes will be huge: about 1 m wide and 0.5 m high. To cover this entire area you need 106 different CCDs (detectors). Most of them are white light CCDs. Additionally there are blue sensitive (BP) and red sensitive (RP) CCDs. About one billion pixels (picture elements) are distributed over the focal plane as each CCD consists of about 9 million pixels. CCD images can have saturated pixels as you may have experienced with your digital camera when taking photos or videos and a bright light source is...

Gaia data processing

In a previous blog entry you have learned about the rehearsals taking place in preparation for the Gaia data processing. Unlike a mission such as the Hubble Space Telescope, Gaia does not produce data that is immediately scientifically useful. The raw telemetry must first be processed before we can obtain the sought after distances, motions, and properties of the stars observed by Gaia. This immense task will be undertaken by a pan-European collaboration, the Gaia Data Processing and Analysis Consortium (DPAC). The DPAC consists of about 450 persons, spread over academic institutes and space agencies throughout Europe and beyond, who are actively contributing to writing the millions of lines of code needed...

IT Phone home

Being an Information Technology (IT) specialist may not sound as glamorous as some of the other roles that people have out here in Kourou, but it is just perhaps just as important since we all rely heavily on our computers and online communications, not only for a successful launch campaign, but also to stay connected with our families thousands of miles away back home. Being an IT specialist in the jungle also presents with it some unique challenges, but the unusual technical problems are probably the most interesting to deal with! I’m no stranger to Kourou launch campaigns, having worked on Rosetta and Herschel and Planck in the past. Before the Gaia...

Operations rehearsal 4

Once Gaia is flying it will send a daily stream of scientific data to Earth. The Missions Operations Centre receive this and transfer it to the Science Operations Centre in the European Space Astronomy Centre (ESAC), the ESA establishment near Madrid in Spain.  At ESAC, “Initial Data Treatment” is carried out as well as running the First Look software to assess the instrument health. The processed data is then sent to the other data processing centres around Europe (Barcelona, Cambridge, Geneva, Turin and Toulouse).  A group of payload experts also look at this data to confirm the performance of the instrument. Depending on what the payload experts find, small changes or calibration...

Gaia goes to L2 – what’s an “ell-two&...

Just like observatories on Earth, space observatories like Gaia like it quiet and dark. In space “quiet and dark” means far away from Earth. At large distances from Earth, the motion of spacecraft are no longer controlled only by the gravity of Earth, but also by other gravitational sources – most prominently by the Sun. The orbital motion of Earth around the Sun also influences the motion of spacecraft. The good thing about these forces – if you are a spacecraft – is that in five locations, all these forces balance out to create a stable location from which to study the wider Universe. These points are called the “Lagrange points”, or...