Tag Archives: L2

… and we got there!

ESA’s billion-star surveyor Gaia is now in its operational orbit around a gravitationally stable virtual point in space called ‘L2’, 1.5 million km from Earth. Via ESA web

Orbits of satellites like Gaia or the James Webb Space Telescope at the L2 Lagrange point. Credit: ESA
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The flight dynamics expertise behind Gaia’s criti...

Today is a big day for the flight dynamics experts who determine and predict trajectories, prepare orbit manoeuvres and determine satellite attitudes. At around 19:58 CET this evening, five of Gaia’s eight thrusters will be commanded to...

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 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...

Another day in the life of a Gaia test engineer

In the middle of last night, we received in Kourou a disturbing call from the Gaia control centre, located in Darmstadt, Germany. Although for us it was middle of the night, it was already morning in the control centre. So what happened? Although often announced in the media as having the biggest camera on board that has ever flown in space, Gaia does not actually take pictures in the sense as you and me taking pictures on a holiday trip. Instead, it rather tracks the stars across its sensors as the telescopes rotates and the field of view moves across the star filled sky. In order to do so, a constant readout...

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...