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
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
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)
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).
25.
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
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