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CCD thermal specifications

CCD thermal specifications. Divers for Telescope thermal architecture. FPA and their detectors Detectors shall be at a temperature lower than -70°C ( TBC ), FPA power dissipation is stable , around 1 watt per telescope

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CCD thermal specifications

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  1. CCD thermal specifications Divers for Telescope thermal architecture CCD thermal specs G Epstein

  2. FPA and their detectors Detectors shall be at a temperature lower than -70°C (TBC), FPA power dissipation is stable , around 1 watt per telescope Only very slow Detectors Temperature fluctuation are acceptable, but few ° drift within a 3 month observation period may be foreseen . Electronics boxes FEE and MEU shall be at temperature higher than - 40°C (electronics components), FEE power dissipation is stable , around 4 watt per telescope FEE short term stability is the only constraint MEU are less sensitive to temporal variations, Telescopes Need an in-flight focus control, 40 mechanisms are inconceivable, but thermal adjustment of the focus (in one way) seems possible, Temperature close to room temperature prefered Stay alive during OFF phases: Heaters to be controled by SVM PLATO CCD Thermal needs Temperature acceptable level , after irradiation in L2 orbit Dark curent < 10 e- EOL Hot pixels under control few % off affected pixels EOL On board software detection ( DPU or ICU) Charge transfer Inneficiency EOL Gaia radiation studies to be analysed leads to specify -100°C in PPD Acceptable drift Temperature must stay under “acceptable level “ Several K in a 3 months observation run is acceptable Temperature stability thermal fluctuation induced photometric noise must stay low regardless to photon noise ( 27 ppm in one hour) CCD thermal specs G Epstein GE + PL PPLC/ESA meeting, Feb 27th 2009

  3. Corot feedbacks Comparable needs Asterosismology and exoplanets detection Same detectors irradiation problems Corot polar Orbit 875 Km altitude Higher integrated irradiation than L2 are Corot 2 years results comparable to 7 years on L2 orbit? Corot CCD : MPP mode Lower Iobsc --> Working temperature - 40°C Is «  normal mode «  evolution similar to MPP mode? GE + PL CCD thermal specs G Epstein PPLC/ESA meeting, Feb 27th 2009

  4. EEV CCD tests shows similar temperature behaviour : 1e-/sec/pixel @ -60°C MPP mode henances by 30° this results 1e-/sec/pixel @ -30°C Dark curent = f(T) before irradiation GE + PL CCD thermal specs G Epstein PPLC/ESA meeting, Feb 27th 2009

  5. At time beeing , in fligth results are beter than this foreseen evolution ( average I obsc < 1e-/px/sec @-39°C) Corot Dark curent after 2 1/2 years irradiation( models) Foreseen evolution of dark curent GE + PL CCD thermal specs G Epstein PPLC/ESA meeting, Feb 27th 2009

  6. COROT Hot Pixels Some pixels becomes « hot » when passing SAA , due to High energy Protons effects inside CCD silicon volume Recovery time is variable ( days, week, months…) Exoplanets “false alerts” to be obercome by software CCD thermal specs G Epstein

  7. Hot pixels amplitude distribution • Hot pixels detected on sky full images starting COROT observation runs • numbers refers to 4kx4K PMM frame transfert CCD • Intensity in e-/32s • Integration time AS 1s • Integration time PF 32s CCD thermal specs G Epstein

  8. Corot Long terme evolution : • Orbite polaire 875 Km , lancement 27 12 2006 • Blindage équivalent 15mm alu /4steradiants • CCD E2V 4280 MPP Frame Transfert • Température -39°C • 2 % stars potentialy affected - Software detection is mandatory but not critical Lecture 1 s Lecture 32 s CCD thermal specs G Epstein

  9. Charge Transfer Inneficiency EOL CTI effet in photometry: Some Gathered photo electrons seems to apears in the adjacent pixel. Disymetral Enlargement PSF equivalent effect. Spot Centroid displacement No detectable effect in Corot Data Need specs for Plato! CCD thermal specs G Epstein

  10. Tentative conclusions • -70°C working temperature plato CCD seems to fulfill needs in terms of dark curent EOL. • Hot pixels behaviour as f(temperature) as to be assesed CCD thermal specs G Epstein

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