Launch anniversary: celebrating Gaia’s 2nd birthday in space

VS06 Soyuz with GAIA, LaunchSoyuz_TMA-19M_launch_647px
Figure 1: Top: Gaia’s launch on a Soyuz-2 rocket (image credit: ESA – S. Corvaja, 2013). Bottom: Tim Peake’s launch on a Soyuz-FG rocket (image credit:

Two years ago today (Saturday 19th December 2015), ESA’s Gaia satellite was launched into space from South America by a Soyuz launch vehicle, operated by Arianespace (see previous MSSL Astro blog for more details. Gaia lifted off at 9.12am UTC (6.12am in French Guiana). On that day, many members of the lab watched the event live on TV and celebrated the successful launch with a champagne breakfast in the MSSL Common Room. One year on and we were back in the MSSL Common Room, celebrating Gaia’s first birthday in space with a fantastic Gaia-shaped cake, decorated to look like Gaia, made by MSSL chef Sue Ford (see previous MSSL Astro blog). Two years on and the launch anniversary falls on a Saturday so we are having a virtual celebration with this blog.

Watching British astronaut Tim Peake’s launch into space on Tuesday 15th December 2015 reminded me of Gaia’s launch. Both were launched using similar Soyuz rockets (see Figure 1), albeit with different versions. I watched Tim’s Kazakhstan launch on TV and saw the four first stage boosters being jettisoned. It was very similar to Gaia’s four boosters being jettisoned after its launch from French Guiana, which I was fortunate enough to witness with my own eyes (see here for more details and a video of Gaia’s launch).

Tim and two other astronauts were transported to the International Space Station, 400 km above the Earth, by a Soyuz-TMA, which is the orbital vehicle where the astronauts sit on top of the Soyuz-FG rocket. Gaia was transported half way round the Earth by a Soyuz Fregat, which is the upper stage of the Soyuz-2 rocket, before they separated and Gaia continued on its one month journey to L2, 1.5 million km from the Earth.

Tim is now officially a space explorer, having beaten me (and 8000 other applicants!) to being an ESA astronaut. While envious of Tim, I am still very fortunate to be exploring space with Gaia! Gaia’s 102 CCDs are our eyes in space as it records light from over 1 billion stars in the Milky Way. Each CCD was tested at MSSL (see the Gaia tab on the MSSL Gaia webpage for more details).

The MSSL Gaia team consists of Mark Cropper (PI and head of MSSL Astro Group), Steve Baker (Project Manager and head of MSSL Software Engineering Group), George Seabroke (Gaia Scientist and member of MSSL Astro Group) and members of the MSSL Software Engineering Group: Howard Huckle, Mike Smith, Kevin Benson and Chris Dolding. Over the last eight years, the MSSL Gaia team has developed about half of the on-ground pipeline (with the other half developed by collaborators around Europe) to process Radial Velocity Spectrometer (RVS) spectra.

The current team helped to commission RVS (see here for more details). Since then further optimisations have already achieved the end of mission specification for radial velocity precision of bright stars (V < 11 mag). The team is currently testing the pipeline ready for the first release of Gaia radial velocities for the 2 million brightest stars in the sky, which will be part of Gaia’s second data release in 2017 (see here for more details).

In two years of observations, Gaia-RVS has collected over 7 billion spectra, making it already the largest spectroscopic survey in history! 7 billion is probably more spectra than have been collected in the history of astronomy pre-Gaia! MSSL’s software will help to combine all the spectra of the same star into combined spectra for around 100 million stars, which will also produce the largest ever radial velocity survey as part of future Gaia data releases.

By @GeorgeSeabroke

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