Monthly Archives: November 2013

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...

Gaia is whole again

After a month full of uncertainties, Gaia transponders are back and in good health. Following their business class return flight to Kourou, both Gaia transponders have been re-integrated in the spacecraft, re-connected, and functionally verified. At the completion of five days of intensive testing, all results were positive, allowing the re-installation of the solar array panels and of the multilayer insulation (MLI) blankets, which had to be removed for operator access (see picture). This progress allows the team to reaffirm the recently agreed launch date of 19 December. As of Monday 25 November, we will be able to resume the spacecraft preparation, beginning with pressurisation of the gas tanks. This is a...

Gaia launch set for 19 December

The checks on the Gaia satellite are proceeding well, enabling the launch to take place on Thursday, 19 December. The exact time of launch is 09:12:18 UTC (10:12:18 CET), which is 06:12:18 local time in French Guiana.

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Guide to our Galaxy

Take a virtual journey through the Milky Way! This virtual journey shows the different components that make up our home galaxy, the Milky Way, which contains about a hundred billion stars. It starts at the black hole at the centre of the Milky Way and with the stars that orbit around it, before zooming out through the central Galactic Bulge, which hosts about ten billion stars. The journey continues through a younger population of stars in the stellar disc, home to most of the Milky Way's stars, and which is embedded in a slightly larger gaseous disc. Stars in the disc are arranged in a spiral arm pattern and orbit the centre...

We are back!

Of course you have all noted that when we started our blog the launch date of Gaia was 20th November and now the countdown to launch shows 20th December. Why is that? Let’s start from the beginning. On Saturday, 19th October, at about 16:30 when I was shutting down the computer in my office in Kourou and preparing for a sunny Sunday, I received a phone call from the person responsible for one of the key systems embarked on the spacecraft. There had been a failure on a satellite already in orbit and the analysis of the failure pointed towards a design mistake. The consequence was that the lifetime of a tiny...

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...