The ECLAIRs telescope onboard the SVOM mission for GRB studies 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

Objectives for : a post-Swift GRB mission 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 Need for a future GRB trigger ! SVOM mission, ECLAIRs trigger 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

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

SVOM : Orbit and Pointing strategy 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 Sun light % Un-obscured Time [10 s] ground telescope 64 33 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

SVOM : Pointing strategy Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp SVOM : Pointing strategy 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) Simulation of detections - 73% GRB visible immediately by 1 out of the 3 large telescope sites - 100% visible in < 12 hr d a Chile Hawaii Canary Islands anti-solar pointing Galactic plane Sco X-1

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

SVOM: Instruments GRM ECLAIRs GRB trigger VT SXT Soft X-ray telescope Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp SVOM: Instruments SVOM : Space-based astronomical Variable Objects Monitor a French-Chinese collaboration with Italian contribution GRM g-ray monitors 0.03-3 MeV, NaI-CsI 2 sr FOV, no localization ECLAIRs GRB trigger CXG (X/g camera) CdTe, 4-250 keV imaging 4-120 keV 2 sr FOV Dr<10 arcmin (prompt) photon timing 10 ms VT Visible Telescope 400-650 & 650-1000 nm 21 x 21 arcmin2 After sat repointing (3 mn) Mag R=23 in 300 s Dr<1 arcsec SXT Soft X-ray telescope 0.3-2 keV, CCD 27 x 27 arcmin2 After sat repointing (3mn) Dr<10 arcsec GFT Ground follow-up telescopes GWAC Ground wide angle camera

ECLAIRs: flight heritage SIGMA & IBIS Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp ECLAIRs: flight heritage SIGMA & IBIS 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° 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)

ECLAIRs: X & Gamma camera (CXG) Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp ECLAIRs: X & Gamma camera (CXG) Management CEA Saclay 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 cm2) sensitive area 1024 cm2 passive cooling (-20°C) Control electronics Total Field of View: 2 sr Localization accuracy: < 10’ Spectral domain: 4 – 250 keV 4 – 120 keV imaging Photon timing: 10 ms All photons on ground < 1 day Detectors Cold plate Read-out electronics Radiator

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

ECLAIRs: Detector performance Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp ECLAIRs: Detector performance Detectors ACRORAD Japan CdTe Schottky (In//Pt) 4 x 4 x 1 mm3 low noise Detector read-out ASIC CEA Saclay low-noise full custom ASIC IDeF-X V2 Low noise 2.5 mW/channel CMOS 0.35 mm Radiation hard > 100 krad Bias voltage 600V Op Temperature -20°C Performances: 1.8 keV FWHM at 60 keV Low energy threshold < 4keV Counts 100 200 300 Energy (keV) 10 40 60 50 20 30 3.5 keV

ECLAIRs : Mask pattern 100 x 100 pixels of 5.4 mm 30% open (red) Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp 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)

ECLAIRs simulation : Deconvolution Stéphane Schanne, CEA ECLAIRs simulation : Deconvolution 1000 s simulation, 4-50 keV X-ray background 1.9 Mcounts Source 640 ph/cm2 at (50,50) sky pixels = 32° off axis 60 Kcounts SNR image = 68 s

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

ECLAIRs simulation : Expected sensitivity Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp ECLAIRs simulation : Expected sensitivity 8s 7s Flux (for 10 s exposure) at detection limit (5.5 s) for various Epeak of GRB Monte Carlo simulation : Background + on axis GRB with spectrum a=-1 b=-3 ECLAIRs particularly sensitive to low energy GRB (Epeak < 30 keV) Highly red-shifted GRB, X-ray rich GRB, X-ray flashes Expected number of GRB triggers : 80 / year

ECLAIRs : Expected localization accuracy Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp ECLAIRs : Expected localization accuracy simulation result source anywhere in field of view 10 s simulation, 4-50 keV band extragalactic background + 1 source localization accuracy = 9 arcmin at 6s Sky pixel fraction (center of FOV: 1 pix = 33 arcmin) good association fraction (x 0.1) theoretical curve SNR simage Detection Threshold 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)

ECLAIRs : Science and Trigger Unit (UTS) Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp ECLAIRs : Science and Trigger Unit (UTS) UTS concepts CXG GRM Mass memory X-band Alert to ground Onboard digital electronics FPGA + Processor Radiation tolerant 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) Design & Developpment CEA Saclay

ECLAIRs : Science and Trigger Unit (UTS) Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp ECLAIRs : Science and Trigger Unit (UTS) Trigger on Count rate increase (in CXG) Count rate increase DN(T,E,Z) continuously checked on logarithmic time slices (10 ms – 40 s), energy bands, detector zones N time (s) -5 10 103 15 103 20 103 40 5 103 counts s-1 2 105 4 105 60 counts s-1 per detector 0.5 1.0 Time (s) after 01:51:44 UT 100 200 0.0 GRB 050904 (Swift) time T T B Time window localize localize localize Imaging trigger Search continuously new source in Time Windows of fixed sizes (20 s – 20 mn) 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

ECLAIRs : Science and Trigger Unit (UTS) Stéphane Schanne - forum SAp 2008 saclay irfu SAp ECLAIRs : Science and Trigger Unit (UTS) 0.1 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 s (noise 6 s) Localization ~ 2 arcmin Peak-flux 1s = 0.66 ph/cm2/s (15-150 keV) Indice spectral 1.4 Time (s) Counts en 20.48 s Sigma image  1000 Earth exit Non-occulted FOV Earth entry

ECLAIRs : Science and Trigger Unit (UTS) Stéphane Schanne - forum SAp 2008 saclay irfu SAp ECLAIRs : Science and Trigger Unit (UTS) 0.1 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 s (noise 6 s) Localization ~ 3 arcmin Peak-flux 1s = 0.66 ph/cm2/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

谢 谢 Summary : SVOM - 闪电 (Shan Dian = Éclairs) Stéphane Schanne - 2008 Nanjing GRB conference saclay irfu SAp Summary : SVOM - 闪电 (Shan Dian = Éclairs) ECLAIRs (g 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 Epeak 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 谢 (thank you!)

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