1. GAIA is a European Space Agency satellite launched in 2013 to create a 3D map of the Milky Way galaxy. 2. It contains three instruments - photometers, spectrometers, and astrometers - that precisely measure the positions, motions, distances, and physical properties of over 1 billion stars. 3. To observe the entire sky, GAIA spins and precesses, taking measurements of each star approximately 80 times over its 5 year mission lifetime. The satellite's measurements enable astronomers to understand the composition, formation, and evolution of our galaxy.

1. 1 All the space you need
GAIA
Crédit:©ESA
GAIA
a science satellite
for 3D dynamic
mapping of the
Milky Way

2. Some observables to describe objects
B
d
d ≈ B /
α
Comparative analysis of distances and physical properties
=> Get rid of distances
=> Perform high accuracy measurements
Crédit:©F.Mignard/Cheveu(BornBadRecords2008)
The position of the image of
a star depends on its
color, the measurement of
the color of the star is
needed => chromaticity
=> astrometry

3. •Several successive observations of the celestial
sphere enable to measure relative motions
between stars, but in 2D => 2D dynamics
mapping
•Radial distance and radial velocity (along observer line of
sight) are missing to complete a complete 3 D dynamics
measurement
 Radial distance: Parallax measurement
 Radial velocity: Doppler effect (light spectrum of a
star is shifted toward blue (short wavelength) when
star is coming closer and shifted to the red when
star is moving away)
=> spectrometry

4. p4
Gaia main objective
Improve star positioning
knowledge by a factor 100,
stars up to magnitude 20
Observe more than one billion of objects, without any a priori
 Position => astrometry + chromaticity correction
 Distance => astrometry
 Proper motion => astrometry + HR spectrometry
 Physical properties => photometry + HR spectrometry
=> 3 instruments on board the spacecraft

5. In order to observe all the sky
• 2 view directions with a 106.5 deg basic angle
• Spin of the satellite in 6 hours
•Modification of the spin axis
At the end of GAIA life, each object should be
have been seen 80 times
Crédit:©F.Mignard,UNS&ObservatoiredelaCôted'Azur/ESA

6. p6
1,5 millions km far away from Earth
There are 5 equilibrium positions
for a 3 body system, one of them
being provided with a marginal
mass. Soleil+Earth+spacecraft
Lagrangian point L2 is well
suited for cosmos observation
= Stability

7. 16 years from concept to launch
Proposal
Concept & Technology Study
Mission Selection
Re-Assessment Study
Phase B1
Scientific operation
Launch 2013
Final
Studies
Data Processing
Implementation
Data Processing
Definition
Operation
Mission Products
Intermediate
Selection of Prime Contractor (EADS Astrium SAS)
Phase B2
Phase C/D
Software Development (DPAC)

8. p8
3 instruments sharing the same focal
plane• Photometry & RVS: spectral dispersion is produced in the image
space, in front of the focal plane => common detection & processing
 Blue & red photometry
with 2 prisms in the FPA
& dedicated CCDs:
 Chromaticity correction
simultaneous to astrometry
 Medium Band Photometry
[330-1000 nm]
 Radial Velocity Spectrometer
with grating & afocal corrector
& 12 dedicated CCDs:
 Spectrometry in [847-874nm]
 Radial Velocity measurement

9. The focal plane
106 CCD, ~ 1 Gpixel

10. p10
10 000 stars/second !

11. p11
Two telescopes combined on the same
focal plane • 2 Three Mirror Anastigmat telescopes M1-M3
aperture 1450x500 mm², focal length f = 35 m
angular separation = basic angle
Common
folding
mirrors
M1
M3
M2
M1
M3
M2
M4
M’
4
M1
M3
M4 - beam
combiner
M2
 Intermediate image used for field discrimination
 Beam combiner at their exit pupil => common FPA
M’1
M1 LOS 2
LOS 1
M’2
M2
M3
M’3
M4/M’4
(combiners)
M5
M6
Common
FPA
LOS1
LOS2M1
M2
M3
M’1
M’2
M’3
Beam combiner
Common
FPA

12. p12
A stable opto-mechanical design
• Full silicon carbide architecture
• Passive thermal design
• Decoupling by release of launch
bipods
M’3
M’2
M1M’1
FPA with
radiators
Isostatic
mounts
PLM
optical
bench
Folding optics structure
with RVS optics
M5
M6
M’4
M4
(CDR design status)

13. The payload in assembly

14. Primary
mirror 1.45 m
x 0.5 m

15. p15
•A nanostructure network (grating plate) spectrometer
provides the required resolution (0.25 Å/pixel)
Spherico-prismatic
lenses
Nanostructure network
(grating plate)
Radial velocity measurement

16. The overall
satellite Instrument
Service Module
Thermal Tent
Sun Shield

17. How to
assemble
the
spacecraft

18. 30/07/2010 Service Module (SVM) arrival in Toulouse
Carbon fiber structure (made by CASA, Spain), Propulsion
elements (CPS system made by ASTRIUM UK, and part of
MPS system made by TAS Italy), electrical harness (CASA),
previously assembled and tested in Stevenage (UK)
22/10/2010, first switch ON of the SVM electrical first
equipments : power, calculator, interfaces and first central
software
October 2011, the SunShield (DSA) is delivered by SENER (Spain)

19. Deployment test of the sunshield in clean
room

20. Autumn 2011 : Mechanical tests
Vibrations, acoustics noise are simulated to the Spacecraft to verify if the
structure and the differents fixations could resist to the future launch
The missing equipments are simulated by loads (for example, the
Payload). The tanks are full of Helium, Nitrogen or Isopropylic alcohol to
simulate the future propellant gaz.
Beginning of 2012, new DSA deployment to verify if it passed successfully the mechanical tests = successful launch

21. Test de vibrations mécaniquesBeginning 2012 : mechanical tests of the Payload
Acceleration up to 10G !

22. April 2012, delivery of the Phase Array Antenna
This antenna will allowed to send the data recorded on board to the Earth
A new step to the complete Spacecraft !

23. Summer 2012, SVM Thermal Vacuum
With captors inside, the SVM is placed into a vacuum chamber
to simulate the temperature into Space. The objectives is to
verify that all the equipments are well running onto vacuum and
that thermal predictions are confirmed.
December 2012, Payload Thermal Vacuum
The performance of the 3 instruments are verify in vaccum and
low temperature (stability, good images, …)

24. February 2013 Payload delivery
GAIA became a complete satellite !
In order to avoid any contamination on mirrors and CCD, the
assembly is done in a class 100 clean room (less than 10000
particles of 0,1µm or less than 30 particles of 1µm in 1m3 air).

26. March 2013, beginning of the final verifications
The spacecraft is measured : weight, Center of gravity, inertia
moment

27. EMC TEST in anechoic chamber
Verification that all equipments
are not « noisy » to others, in
particular the PAA

29. Automn 2013: launch on Soyouz from Kourou, french Guyana

30. Key Numbers
 Mass spacecraft at launch : 2 100 kg
 Mass propellant : 300 kg
 Diameter of the Sunshield in orbit configuration : 10 m
 Primary mirrors : 1.45 m x 0.5 m
 Focal Distance : 35 m
 CCD : 1 Gpixels @ 160 K
 Mass memory : 1 Tb
 Science Telemetry : 10 Mbits/s
With about 100 Go of data each day, 1 Peta-octet (1000 To)
of data at the end of the GAIA mission !

31. News about GAIA on my blog :
http://idariane.wordpress.com
On ESA page :
http://sci.esa.int