1. 1 GAIA System Level Technical Reassessment Study Final Presentation ESTEC, April 23rd 2002 Part 1b Development & AIV

2. Contents 1- AIV approach 2- Schedule 3- Costing approach

3. PLM Model philosophy –PLM SM (structural model), with flight structure, dummy units and blank mirrors. Used for mechanical qualification at satellite level, including alignment stability verification. The thermal validation is proposed at PFM level. –PLM EO-EM (electro-optical engineering model), with EM CCD & video electronics chains. Used to validate data acquisition and processing. –PLM PFM, all flight hardware, for full proto-flight qualification at module / satellite levels. SVM Model philosophy –SVM SM, with flight structure and propulsion, SM units and solar array, dummy sunshade. Used for mechanical qualification at satellite level. –SVM AVM, (Avionics Model), consisting in a « flat » assembly of EM or FM electrical units. Used for avionics & software validation. –SVM PFM, all flight hardware, for full proto-flight qualification at module / satellite levels. Satellite Model Philosophy (1/2)

4. Satellite Model Philosophy (2/2) Satellite Model Philosophy: three models –SM model, made of the assembly of PLM-SM and SVM-SM. Used for satellite-level mechanical qualification. –AVM model, made of the SVM AVM complemented by the EM payload data handling electronics (PDHE) having direct interfaces with the SVM. Used for satellite-level avionics validation (mainly: payload interfaces, AOCS closed loop). –PFM model, made of the assembly of PLM-PFM and SVM-PFM. Used for satellite-level full proto-flight qualification, and ground segment interface system test.

5. SA Dummy A.I. SVM PFM structure SM Units Mechan. Testing Static load (qualif.) Mechan. Testing Fit check Shock test A.I. PLM PFM structure Dummies & Mirror Blanks Mechan. Testing Static load (qualif.) A.I. PLM-SM Mechan. Testing Acoustic test Sine vibration qual test µ setting SVM-SM Propulsion dummies Metrology PLM thermal tent A.I. Refurbishment & PFM activities Sunshield Dummy A.I. SM Units SM Spacecraft AIV flow : SM validation

6. CDMU EM PCDU EM SVM avionic bench PLM-EM Elec. reference tests Software tests Function. & Perfo. Testing Function. & Perfo. Testing Avionic bench Function. & Perfo. Testing Astro VPU EM Astro FPA EM Function. & Perfo. Testing Function. & Perfo. Testing Photometer VPU EM Photometer FPA EM Function. & Perfo. Testing Function. & Perfo. Testing RVS FPA EM Function. & Perfo. Testing RVS VPU EM PDHE EM FEEP EM &simul. Function. & Perfo. Testing Star tracker PFM Sun sensor simul. MGA EM & simul. Function. & Perfo. Testing SSMM EM Function. & Perfo. Testing PDHE simul. Spacecraft avionic bench Function. & Perfo. Testing PDHE EM Function. & Perfo. Testing AIV flow : Avionic bench

7. A.I. Refurbshmt SVM structure PLM structure A.I. PFM units At ambiant SVM Software tests A.I. PFM Optics Function. & Perfo. Testing At ambiant Function. & Perfo. Testing Perfo in vacuum thermal vacuum thermal balance thermoelastic behaviour Mechan. Proto-Qualif EMC Test A.I. PFM FPAs & Elec. units At ambiant PFM Spacecraft Thermal Acceptance Reference measurt Thermal balance SVM + SL Thermal vacuum SVM Control measurt Reference measurt Acoustic test Sine vibr. Test Fit-check Control measurt Conducted Radiated Function. & Compat. Test RF & Gnd Segt Compatib. Test SVM-PFM PLM-PFM Reference measurt Software tests Function. & Perfo. Testing Function. & Perfo. Testing A.I. Sunshield PFM Deployment test Pyro test SS deployment testt SL-SM RF tests Final software tests SL//ground segment tests SA PFM Propulsion PFM A.I. AIV flow : PFM validation

8. 1 - AIV approach 2- Schedule 3- Costing approach Contents

9. Gaia Programme Overall Schedule

10. Satellite schedule

11. Critical paths are: –FPA & electronics EM – FPA & electronics FM – PLM PFM AIT – SL PFM AIT where detectors, but also electronics planning must be carefully managed. => Electronics shall predeveloped by technology programmes –PLM PFM optics – PLM PFM AIT – SL PFM AIT –PVM (& SLM) structures – SM SL tests – PLM PFM AIT - SL PFM AIT as SVM shall not be on the critical path of the payload, we have chosen to postpone the AIT of RCS PFM after the SM SL tests. The total development lasts 58 months, up to satellite delivery. Schedule analysis

12. Contents 1- AIV approach 2- Schedule 3- Costing approach

13. Product Tree

14. Work Breakdown Structure

15. 2 options are considered : –Option 1 : Astrium as Spacecraft Prime, SL AIV and PLM Contractor SVM is sub-contracted –Option 2 : Astrium as Spacecraft Prime and PLM Contractor, SVM is sub-contracted Satellite AIV is sub-contracted Reference Industrial Organisation

16. First objective = use of Soyuz instead of Ariane 5 –Present status indicates that this is OK, at (almost) no penalty for the astrometric performance; Spectro performance improved. –Launch mass is compatible with a Soyuz ST 2-1A from Baikonour (growth potential). Second objective = reduce satellite cost –Overall satellite design (especially the payload) has been made simpler, more robust and safer for science goals achievement (see next view-graph) –SVM should benefit from a good reusability of a Planck-type platform, for which the time-lag is adequate (Planck is only 3 years ahead of Gaia). Further activities during the end of the study will aim at consolidating this encouraging status. Conclusion at Final Presentation