1 / 8

Space Telescope Imaging Spectrograph: Projected Performance through 2013

Space Telescope Imaging Spectrograph: Projected Performance through 2013. Paul Goudfrooij STScI. Part of procedure to address necessity of ASCS installation CCD and MAMA Performance Estimates with/without ASCS Science Impact example. CCD Performance after SM4.

jeanne
Download Presentation

Space Telescope Imaging Spectrograph: Projected Performance through 2013

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Space Telescope Imaging Spectrograph: Projected Performance through 2013 Paul Goudfrooij STScI Part of procedure to address necessity of ASCS installation CCD and MAMA Performance Estimates with/without ASCS Science Impact example

  2. CCD Performance after SM4 • Main contributor of effective throughput loss is increase of Charge Transfer Inefficiency (CTI = 1–CTE) with time (due to accumulated radiation damage) • Performance degradation continues in current Safe mode • Functional dependence of CTI on source counts, background level, and elapsed on-orbit time determined in 2003 (Goudfrooij & Bohlin) • CCD spectroscopy mode unique to STIS and hence deemed most relevant for current exercise • Issues related to growth of number of hot pixels similar to those for ACS CCDs (cf. Marco’s talk), but can be mitigated by dithering • On-orbit increase of dark current typically has less impact than that of CTI for faint sources • No positive impact of ASCS/STIK expected on CCD performance • Effect of higher temp’s on CTI would need to be calibrated in flight

  3. Science Impact of CTI Increase • Example of popular use of STIS CCD: Measurement of Black Hole Mass in center of typical bulge in low-mass galaxy (plenty of medium-and high-mass galaxies already done). • SETUP: • G750M/8561 Å • 52x0.2 slit • CCD binning 2x1 • galaxy with V = 16 mag/arcsec2

  4. NUV-MAMA on NUV-MAMA off FUV-MAMA Performance after SM4 • Dark Current Limited: Exp time needed  Dark Counts • FUV-MAMA dark in “glow” region generally increasing with tube temp, but no clear relation between the two. • relation between dark in glow region and time since HV turn-on • If tube temp will rise significantly after SM4, might consider constraining use to only few hours after every HV turn-on Echelle data F1 apertures

  5. SM3B Solar Max SM3A FUV-MAMA Performance after SM4 • Past Long-term Evolution of FUV-MAMA Temperature • Overall increase with time, but rate of increase declining • Temp stayed ~ constant with time since 2002 Note: Tube Temp is ~ 4 ºC lower than Charge Amp Temp (latter shown on left)

  6. NUV-MAMA Performance after SM4 • NUV-MAMA Dark Current • Due to phosphorescence in impurity sites in MgF2 window, where e– can be in metastable level just below level decaying to emit  • Dark level strongly dependent on thermal environment • Long-term history of dark current (and temp) shows leveling off Plot by James Davies SM3B Solar Max SM3A

  7. NUV-MAMA Performance after SM4 • Dark can be substantially reduced with ASCS/STIK • Temp’s (and hence dark and exp time for dark-limited obs.) down by nearly factor of 2 • Dark down extra factor ~2 if cooling campaigns established • Would open up whole new field of applications • Echelle spectroscopy of absorption lines in faint, distant QSOs • NUV imaging of distant, low surface brightness galaxies Model of dark during cooling campaign Approx. current dark level

  8. Summary of potential impact of ASCS on STIS performance

More Related