Nanjing Gamma-Ray Burst conference , 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

Stéphane Schanne 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

Future GRB mission: SVOM SVOM SVOM : Space-based Variable astronomical Objects Monitor a French-Chinese collaboration with Italian contribution Stéphane Schanne 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)

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 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

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 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

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

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

GRANAT: Soviet satellite SIGMA : French telescope First coded mask aperture space-telescope “Système d'imagerie gamma à masque aléatoire” CEA Saclay, CESR Toulouse, IKI Moscow 35 keV MeV Localization ~ 3 arcmin Total field of view ~ 30° x 30° Stéphane Schanne Nanjing GRB conference saclay irfu SAp ECLAIRs: flight heritage SIGMA & IBIS INTEGRAL: esa satellite 2002 ( ?) 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)

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 Nanjing GRB conference saclay irfu SAp ECLAIRs: X & Gamma camera (CXG) Cold plate Detectors Read-out electronics Radiator Control electronics

Stéphane Schanne 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

Detectors ACRORAD Japan CdTe Schottky (In//Pt) 4 x 4 x 1 mm 3 low noise Stéphane Schanne Nanjing GRB conference saclay irfu SAp ECLAIRs: Detector performance Counts Energy (keV) 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

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 Nanjing GRB conference saclay irfu SAp

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 

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

ECLAIRs simulation : Expected sensitivity 88 77 Stéphane Schanne 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

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 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

Stéphane Schanne 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

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) counts s -1 time (s) counts s -1 per detector Time (s) after 01:51:44 UT GRB (Swift) Stéphane Schanne Nanjing GRB conference saclay irfu SAp ECLAIRs : Science and Trigger Unit (UTS)

Stéphane Schanne - forum SAp 2008 saclay irfu SAp cnt/s/pix s SWIFT UTS software model (image trigger) - background, Earth transit in FOV - GRB (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 ( keV) Indice spectral 1.4 ECLAIRs : Science and Trigger Unit (UTS) Time (s) Counts en s Sigma image  1000 Earth exit Non-occulted FOV Earth entry

Stéphane Schanne - forum SAp 2008 saclay irfu SAp cnt/s/pix s SWIFT UTS software model (image trigger) - background, Earth transit in FOV - GRB (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 ( keV) Indice spectral 1.4 Counts en s Sigma image  1000 Time (s) Earth exit Non-occulted FOV Earth entry ECLAIRs : Science and Trigger Unit (UTS)

Stéphane Schanne 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!)

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