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Nanjing Gamma-Ray Burst conference 2008 06 23-27, 南京 , China

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)

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Nanjing Gamma-Ray Burst conference 2008 06 23-27, 南京 , China

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  1. Nanjing Gamma-Ray Burst conference2008 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. saclay irfu SAp Stéphane Schanne - 2008 Nanjing GRB conference 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

  3. saclay irfu SAp ECLAIRs Coded mask telescope (GRB trigger) Stéphane Schanne - 2008 Nanjing GRB conference Future GRB mission:SVOM SVOM : Space-based Variable astronomicalObjects 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 Phases 0 : began 3/2006 A : began 3/2007 B : expected 9/2008 Launch ~ 2013 Low Earth Orbit (~600 km, 30° incl) Payload ~ 350 kg Platform: 3 axis stabilized repointing capability 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

  4. SVOM :Orbit and Pointing strategy saclay irfu SAp • 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 64 33 mn % Un-obscured ground telescope Sun light Time [10 s] • Orbit: altitude 600 km, inclination 30° • south Atlantic anomaly in Earth magnetic filed high background count rate trapped charged particles • 87% live-time

  5. SVOM :Pointing strategy saclay irfu SAp d Canary Islands Hawaii Galactic plane Chile anti-solar pointing Sco X-1 Stéphane Schanne - 2008 Nanjing GRB conference a • 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

  6. VHF : real-time Alert system saclay irfu SAp Stéphane Schanne - 2008 Nanjing GRB conference 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)

  7. saclay irfu SAp 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 Stéphane Schanne - 2008 Nanjing GRB conference SXTSoft X-ray telescope 0.3-2 keV, CCD 27 x 27 arcmin2 After sat repointing (3mn) Dr<10 arcsec SVOM:Instruments SVOM : Space-based astronomical Variable Objects Monitor a French-Chinese collaboration with Italian contribution GFT Ground follow-up telescopes GWAC Ground wide angle camera

  8. saclay irfu SAp 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 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:flight heritage SIGMA & IBIS

  9. saclay irfu SAp Stéphane Schanne - 2008 Nanjing GRB conference 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

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

  11. saclay irfu SAp • 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 Stéphane Schanne - 2008 Nanjing GRB conference 300 3.5 keV 200 Counts 100 0 10 20 30 40 50 60 Energy (keV) ECLAIRs:Detector performance • Detectors • ACRORAD Japan • CdTe Schottky (In//Pt) • 4 x 4 x 1 mm3 • low noise • Bias voltage 600V • Op Temperature -20°C • Performances: • 1.8 keV FWHM at 60 keV • Low energy threshold < 4keV

  12. ECLAIRs : Mask pattern saclay irfu SAp Stéphane Schanne - 2008 Nanjing GRB conference 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)

  13. ECLAIRs simulation : Deconvolution Stéphane Schanne, CEA • 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

  14. ECLAIRs simulation : Expected efficiency saclay irfu SAp Stéphane Schanne - 2008 Nanjing GRB conference 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)

  15. ECLAIRs simulation : Expected sensitivity saclay irfu SAp Stéphane Schanne - 2008 Nanjing GRB conference 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

  16. ECLAIRs : Expected localization accuracy saclay irfu SAp Stéphane Schanne - 2008 Nanjing GRB conference • 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)

  17. ECLAIRs : Science and Trigger Unit (UTS) saclay irfu SAp CXG Mass memory X-band UTS Alert to ground UTS concepts Stéphane Schanne - 2008 Nanjing GRB conference GRM • 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 Design & Developpment CEA Saclay

  18. ECLAIRs : Science and Trigger Unit (UTS) saclay irfu SAp 1.0 4 105 20 103 15 103 2 105 counts s-1 counts s-1 10 103 0 5 103 -5 time (s) 60 -5 time (s) 40 0.5 counts s-1 per detector • Imaging trigger • Search continuously new source in Time Windows of fixed sizes (20 s – 20 mn) Stéphane Schanne - 2008 Nanjing GRB conference localize localize localize localize 0.0 0 100 200 Time (s) after 01:51:44 UT GRB 050904 (Swift) • 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 T T B Time window localize localize • 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

  19. ECLAIRs : Science and Trigger Unit (UTS) saclay irfu SAp 0.1 0 SWIFT cnt/s/pix 0 100 200 300 s Counts en 20.48 s Sigma image  1000 Earthexit Earthentry Non-occulted FOV Stéphane Schanne - forum SAp 2008 Time (s) • 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

  20. ECLAIRs : Science and Trigger Unit (UTS) saclay irfu SAp 0.1 0 SWIFT cnt/s/pix 0 100 200 300 s Counts en 20.48 s Sigma image  1000 Earthexit Earthentry Stéphane Schanne - forum SAp 2008 Non-occulted FOV Time (s) • 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

  21. Summary :SVOM- 闪电(Shan Dian = Éclairs) saclay irfu SAp Stéphane Schanne - 2008 Nanjing GRB conference • 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!)

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

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