Michael Perryman was the scientific leader of ESA’s Hipparcos space astrometry mission, and with Lennart Lindegren from Sweden, one of the two originators of the Gaia mission. Michael is currently Bohdan Paczynski Visiting Fellow at the School of Astrophysical Sciences, Princeton and Adjunct Professor in the School of Physics, University College Dublin. Here he shares his ringside view of the launch.
19 December 2013: Today, at 06:12 local time here in French Guiana, the Gaia satellite was delivered into orbit, on its way to its surveying location, the Sun-Earth Lagrange point L2. So began the latest and most revolutionary journey in the history of the measurement of the positions of the stars. Placed in orbit by the 1812th launch of the vast Russian Soyuz programme (their 6th from French Guiana), Gaia marks the 40th launch for ESA, and the 25th scientific satellite lofted by Arianespace. To wish it well on its historic journey were a representation of Gaia scientists, ESA project managers and engineers headed by ESA’s Director of Science Alvaro Gimenez, industrial leaders, national delegates to ESA, and senior representatives from numerous other fields of the increasingly ambitious European space programme.
Gaia first appeared as a proposal for consideration in ESA’s space programme in 1993, hot on the heels of ESA’s revolutionary Hipparcos star-mapping mission launched in 1989. Seven years of careful study led to its acceptance by ESA’s Science Programme Committee in 2000, with a target launch date of 2012. Maintaining such an aggressive schedule, for such an ambitious mission at the forefront of so many areas of space technology, is almost unheard of. Managed by ESA, with manufacture, integration and testing contracted to the mission’s prime contractor, Astrium Toulouse, the Gaia industrial consortium comprised 47 European and three US industrial partners. It will map the stars at unprecedented and almost incomprehensible levels of accuracy. The largest instrument built in silicon carbide, Gaia also comprises the largest billion-pixel CCD focal plane ever conceived.
Shipped out from Europe in August, the launch countdown started at t-11 hours. At t-30 min, all systems were go, and weather conditions were perfect. As dawn broke over the Atlantic coast of French Guiana, just outside Kourou, the final 10 second countdown began. Silence fell over the assembled spectators as lights began to flicker amongst the trees on the horizon, then the sky lit up, the ground rumbled beneath us, and the colossal Soyuz powered into the sky. Hidden for a few moments by a thin layer of cloud, Soyuz appeared majestically seconds later, carrying its celestial surveyor in an awesome display of terrifying power. At 170km altitude the upper stage continued to carry Gaia almost vertically upwards. At 38 min after lift-off, no longer visible but with its tell-tale vapour trail streaked across the sky, the launcher orientated the satellite in the direction of L2, before successfully releasing Gaia, now racing away from Earth. Already under the control of ESA’s space operations centre ESOC, in Germany, and just 77 minutes after launch, the next most critical phase of the satellite’s pioneering odyssey, was successfully executed – the deployment of the colossal 10m diameter solar array and sunshield.
It was a perfect injection into the transfer to L2. It will still be a 20-day journey to the isolated expanse of L2, where Gaia will be ‘parked’. From that location, a lengthy process of payload commissioning will precede the 5-year operational phase. Gaia’s goal: to revolutionise the understanding of our Galaxy, and the stars within it.
The most crucial and spectacular step in the execution of all space missions has been passed. After more than a decade of intense dedication, colossal effort, and vast ingenuity, the make-or-break moment of every space mission was decided, in Gaia’s favour, within just a few short minutes. As Arianespace Chairman and CEO, Stéphane Israel, described it “Gaia is a technological marvel, which should make Europe proud of its space industry”.