1. Nanjing Gamma-Ray Burst conference 2008 06 23-27, 南京, China The ECLAIRs telescope onboard the SVOM mission for GRB studies - SVOM mission - pointing strategy - alert network (VHF) - ECLAIRs instrument - on-board trigger (UTS) Stéphane SCHANNE (1) Pierre MANDROU (2) Bertrand CORDIER (1) (1) CEA/IRFU/SAp Saclay (2) CNRS/CESR Toulouse

2. Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp Objectives for : a post-Swift GRB mission Future GRB observations ? SWIFT, how long will it last? 4 more years (~2012) GLAST, not a GRB optimized mission LAT : sensitive to the subsample of high energy GRB GBM : low localization accuracy Objectives : -Provide a GRB trigger to the community -Optimized for X-ray rich (red-shifted, high z GRB) -Determine precise localization < 10 arcmin -Transmit to ground rapidly (< 1 min) for ground follow-up -Provide on-board X-ray and Visible-band follow-up of afterglow -Refine localization < 10 arcsec with on-board afterglow obs. -Optimized ground follow-up capabilities Need for a future GRB trigger ! SVOM mission, ECLAIRs trigger

3. Future GRB mission: SVOM SVOM SVOM : Space-based Variable astronomical Objects Monitor a French-Chinese collaboration with Italian contribution Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp Cn: CNSA, CAS, SECM, NAOC, XIOPM, IHEP Fr: CNES, CEA, CESR, APC, IAP, LAM, OHP, LATT It: ASI, INAF, IASF Phases 0 : began 3/2006 A : began 3/2007 B : expected 9/2008 Launch ~ 2013 Low Earth Orbit (~600 km, 30° incl) PapersSchanne et al; Cordier et al; Claret et al; Basa et al (2008) all in AIP conf proc, Santa Fe GRB workshop, Nov 2007 Payload ~ 350 kg Platform: 3 axis stabilized repointing capabilityECLAIRs Coded mask telescope (GRB trigger)

4. Sun light % Un-obscured Time [10 s] ground telescope 6433 mn Pointing strategy: keep satellite pointing into night direction (~anti-solar) center of FOV above (>40°) horizon for tropical-zone telescopes (Chile, Canaries, Hawaii)  Allow follow-up observation by large telescopes for ¾ GRB  Average 67% of FOV un-obscured by Earth  Reduces thermal constraints Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp SVOM : Orbit and Pointing strategy Orbit: altitude 600 km, inclination 30°  south Atlantic anomaly in Earth magnetic filed high background count rate trapped charged particles  87% live-time

5. Anti-solar within 45° Avoid to point towards Galactic plane and bright X-ray sources (e.g. Sco X-1 in FOV doubles bkg count rate) Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp   Chile Hawaii Canary Islands anti-solar pointing Galactic plane Sco X-1 ► Simulation of detections - 73% GRB visible immediately by 1 out of the 3 large telescope sites - 100% visible in < 12 hr SVOM : Pointing strategy

6. HETE (2° inclination) 15 stations SVOM (30° inclination) 38 stations (redundancy) Inherited from HETE-2 137 MHz, ~600 bit/s VHF receiver - Antenna + Radio receiver - Computer + Internet Alert distribution < 1 mn to robotic telescopes Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp VHF : real-time Alert system

7. SVOM: InstrumentsECLAIRs GRB trigger CXG (X/g camera) CdTe, 4-250 keV imaging 4-120 keV 2 sr FOV  r<10 arcmin (prompt) photon timing 10  s SXT Soft X-ray telescope 0.3-2 keV, CCD 27 x 27 arcmin 2 After sat repointing (3mn)  r<10 arcsec VT Visible Telescope 400-650 & 650-1000 nm 21 x 21 arcmin 2 After sat repointing (3 mn) Mag R=23 in 300 s  r<1 arcsec GRM  -ray monitors 0.03-3 MeV, NaI-CsI 2 sr FOV, no localization GFT Ground follow-up telescopes GWAC Ground wide angle camera Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp SVOM : Space-based astronomical Variable Objects Monitor a French-Chinese collaboration with Italian contribution

8. GRANAT: Soviet satellite 1989 - 1998 SIGMA : French telescope First coded mask aperture space-telescope “Système d'imagerie gamma à masque aléatoire” CEA Saclay, CESR Toulouse, IKI Moscow 35 keV - 1.3 MeV Localization ~ 3 arcmin Total field of view ~ 30° x 30° Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp ECLAIRs: flight heritage SIGMA & IBIS INTEGRAL: esa satellite 2002 (- 2012 ?) IBIS : French-Italian coded mask telesc. ISGRI : French detection plane First CdTe detector in space (16386 pixels) CEA Saclay 15 keV – 500 keV Localization ~ 1 arcmin Total field of view ~ 20° x 20° detects 1 GRB / month (small FOV)

9. Coded Aperture Mask Ta foil (0.6 mm thick) 100  100 pixels of 5.4 mm Open fraction 30% Mask-Detector distance 46 cm Lateral shielding Pb, Cu, Al (block X-ray background) Detection Plane CdTe pixels 4  4  1 mm 80  80 pixels (36  36 cm 2 ) sensitive area 1024 cm 2 passive cooling (-20°C) Total Field of View: 2 sr Localization accuracy: < 10’ Spectral domain: 4 – 250 keV 4 – 120 keV imaging Photon timing: 10  s All photons on ground < 1 day Management CEA Saclay Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp ECLAIRs: X & Gamma camera (CXG) Cold plate Detectors Read-out electronics Radiator Control electronics

10. Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp ECLAIRs: Detection plane (DPIX) Detection plane assembly CESR Toulouse 200 detector modules  32 pixels (XRDPIX) Thermal connectors Electrical connectors Cold plate (AlBeMet) read-out electronics (ELS) control electronics (UGD) ASIC ceramics Detector ceramics CdTe pixels High Voltage grid

11. Detectors ACRORAD Japan CdTe Schottky (In//Pt) 4 x 4 x 1 mm 3 low noise Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp ECLAIRs: Detector performance Counts 100 200 300 0 Energy (keV) 1040 6050 2030 3.5 keV Detector read-out ASIC CEA Saclay low-noise full custom ASIC IDeF-X V2 Low noise 2.5 mW/channel CMOS 0.35  m Radiation hard > 100 krad Bias voltage 600V Op Temperature -20°C Performances: 1.8 keV FWHM at 60 keV Low energy threshold < 4keV

12. ECLAIRs : Mask pattern 100 x 100 pixels of 5.4 mm 30% open (red) Biased random pattern - in order to allow a selfholding structure - good deconvolution properties 120 x 120 pixels of 4.5 mm matrix after rebinning onto detection plane pixel size (used for deconvolution) Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp

13. Stéphane Schanne, CEA ECLAIRs simulation : Deconvolution 1000 s simulation, 4-50 keV X-ray background 1.9 Mcounts Source 640 ph/cm 2 at (50,50) sky pixels = 32° off axis 60 Kcounts SNR image = 68 

14. ECLAIRs simulation : Expected efficiency Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp ECLAIRs good mask opacity (Ta 0.6  m) good detector efficiency (CdTe)  imaging domain 4-50 keV (nominal) 4-120 keV (extended) Ta fluorescence Cd & Te fluorescence

15. ECLAIRs simulation : Expected sensitivity 88 77 Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp Flux (for 10 s exposure) at detection limit (5.5  ) for various E peak of GRB Monte Carlo simulation : Background + on axis GRB with spectrum   ECLAIRs particularly sensitive to low energy GRB (E peak < 30 keV) Highly red-shifted GRB, X-ray rich GRB, X-ray flashes Expected number of GRB triggers : 80 / year

16. ECLAIRs : Expected localization accuracy Sky pixel fraction (center of FOV: 1 pix = 33 arcmin) SNR  image theoretical curve simulation result source anywhere in field of view 10 s simulation, 4-50 keV band extragalactic background + 1 source good association fraction (x 0.1) localization accuracy = 9 arcmin at 6  Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp Intrinsic localization accuracy (radius at 90% CL, statistical error only) at detection threshold~10 arcmin for bright sources ~ 2 arcmin (systematic effects not yet taken into account) Detection Threshold

17. Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp Data acquisition from cameras (CXG, GRM) Trigger on appearance of new source Localization on the sky (mask pattern deconvolution) Real-time alert (< 10 s) - to ground - to slew satellite (SXT & VT follow-up) Onboard digital electronics FPGA + Processor Radiation tolerant UTS concepts CXG GRM UTS Mass memory X-band Alert to ground ECLAIRs : Science and Trigger Unit (UTS) Design & Developpment CEA Saclay

18. localize  Imaging trigger Search continuously new source in Time Windows of fixed sizes (20 s – 20 mn)  Trigger on Count rate increase (in CXG) Count rate increase  N(T,E,Z) continuously checked on logarithmic time slices (10 ms – 40 s), energy bands, detector zones T B T N time Time window  Localization - shadowgram integrated on Time Window (detection plane image) - sky image reconstruction (deconvolution with mask pattern, FFT) - search for maxima in sky image (significant excess) => sky pixel ~ 30 arcmin - eliminate known sources (using a catalog & sat attitude) - fine localization of source (fit inside sky pixel) => localization < 10 arcmin - Send alert to ground - Initiate a satellite slew maneuver localize time (s)-5 10 10 3 15 10 3 20 10 3 40 5 10 3 counts s -1 time (s)-5 2 10 5 4 10 5 60 0 counts s -1 per detector 0.5 1.0 Time (s) after 01:51:44 UT 0100200 0.0 GRB 050904 (Swift) Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp ECLAIRs : Science and Trigger Unit (UTS)

19. Stéphane Schanne - forum SAp 2008 saclay irfu SAp 0.1 0 cnt/s/pix 0 100 200 300 s SWIFT UTS software model (image trigger) - background, Earth transit in FOV - GRB 05094 (SWIFT z=6.3) extrapolate into 4-50 keV  Real-time detection at 40  (noise 6  )  Localization ~ 2 arcmin Peak-flux 1s = 0.66 ph/cm 2 /s (15-150 keV) Indice spectral 1.4 ECLAIRs : Science and Trigger Unit (UTS) Time (s) Counts en 20.48 s Sigma image  1000 Earth exit Non-occulted FOV Earth entry

20. Stéphane Schanne - forum SAp 2008 saclay irfu SAp 0.1 0 cnt/s/pix 0 100 200 300 s SWIFT UTS software model (image trigger) - background, Earth transit in FOV - GRB 05094 (SWIFT z=6.3) repeat 3  extrapolate into 4-50 keV + reduce intensity by 4  Real-time detection at 17  (noise 6  )  Localization ~ 3 arcmin Peak-flux 1s = 0.66 ph/cm 2 /s (15-150 keV) Indice spectral 1.4 Counts en 20.48 s Sigma image  1000 Time (s) Earth exit Non-occulted FOV Earth entry ECLAIRs : Science and Trigger Unit (UTS)

21. Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp Summary : SVOM - 闪电 (Shan Dian = Éclairs) ECLAIRs (  camera + trigger) good efficiency low energy threshold (4 keV) XRR, low + high-z GRB, XRF optimized trigger count rate increase trigger + image trigger GRB localization alert accuracy < 10 arcmin sent in < 1 mn to ground light curves in several energy bands optimized pointing strategy improved ground based follow-up SVOM E peak determination in real-time (up to ~MeV: GRM) Slew maneuver (~3 mn) SXT: X-ray follow-up, refined error box (< 10 arcsec) VT : optical follow-up, refined error box (< 1 arcsec) 谢 (thank you!)

22. 谢 谢谢 谢 Paper : 4 pages, dead-line end of August