GEPI

Between 14th and 16th of June, the GEPI has hosted the bi-annual meeting of the
team which is responsible for preparing the Gaia spetroscopic data processing.

Our lab has a leading role in this process : the team
(gathering 45 active members across 5 european countries and 12 institutes) is
coordinated by David Katz, assisted by Frédéric Meynadier, members of the
"Stellar and Galactic Physics" team. Other team members are heavily involved:
Yves Viala is responsible for the whole "Radial Velocity determination" part,
while Céline Delle Luche works on the corresponding software. Françoise Crifo
establishes a list of radial velocity standards, which will be useful not only
for Gaia but also for ground-based observations. Frédéric Royer computes
spectral masks that will allow to perform those measurements. Paola Sartoretti
is our link to the simulations, for which she develops code.

The IMCCE (Daniel Hestroffer, Pedro David) is also involved, through the
calculations on asteroids that will help calibrating the instrument during
flight.

The main co-responsible for this data processing chain is the Mullard Space
Science Laboratory (MSSL), UK) and we also collaborate with teams from
Montpellier, Nice, Brussels, Liège, Antwerp, Geneva, Potsdam...
The CNES is responsible for running the code we develop and will host the data center during the operational phase.

Code development for processing the data from the Gaia spacecraft (launch due in
2012) is divided in 6-month cycles, which end with a meeting of all teams
within the DPAC (Data Processing and Analysis Consortium). Those meetings allow
to draw conclusions on the previous cycle and build the planning and objectives
for the next one. The goal is to reach, before Gaia’s launch, a complete
processing chain that will be able to cope with the satellite’s telemetry as
soon as it begins to arrive. The coordination unit #6 (CU6) is devoted to
the processing of data incoming from the Radial Velocity Spectrometer, whose
purpose is to determine the source’s radial velocity and atmospheric parameters.

The meeting that took place at the beginning of this month was the kick-off
meeting for the 9th cycle of development. Several major milestones have been
reached during the previous cycle. For example, we managed to assemble for the
first time some of the processing chains and made our code ready for the first
"End-to-end" tests that will allow to validate the interfaces between various
pieces of software. We also had to integrate the latest measurements from the
"flight-model" hardware that begins to be delivered to Astrium, which is
responsible for building the satellite itself. Performances are now know more
precisely and numerous code development have been (and will continue to be !)
necessary to take all that into account in the instrument’s calibration.