STIS Status TIPS, September 17, 2009 Charles Proffitt for the STIS team

STIS Status: Topics STIS SMOV & Calibration Overview STIS CCD status summary NUV Dark current update

STIS SMOV Status All STIS SMOV observations complete as of September 6, 2009 Most STIS SMOV analysis complete –Final superbias & super-dark reference files for SMOV period have been delivered –New CCD reference file delivered Readnoise, gain, and CTE parameters –CCD TDS reference files delivered Time-dependent sensitivity corrections to flux calibration Open issues in STIS SMOV analysis –Waiting for additional Cycle 17 calibration observations to finalize MAMA TDS updates Changes from pre-repair predictions appear to be small (< 3%) – Monitoring of NUV MAMA dark is being continued by cycle 17 calibration program –Detailed writeups still pending for most activities

STIS ActivityPropIDSTIS SMOV Program TitleAnalysis Lead Visits Done Total Visits Status STIS Memory Load and DumpBS11Complete STIS Science Data Buffer CheckBS33Complete STIS Mechanism Mini-FunctionalTW11Complete STIS CCD Anneal (two anneal iterations)MW66Complete STIS CCD FunctionalDL44Complete STIS CCD Dark & Bias MonitorMW90105Complete STIS Aperture Wheel & Lamp FunctionalWZ22Complete STIS STIS-to-FGS AlignmentCP11Complete STIS CCD Spectral Format VerificationWZ11Complete STIS External Focus CheckCP43+1Complete STIS Corrector and Focus AlignmentCP-8Contingency STIS CCD External Spectroscopic QualityTG11Complete STIS CCD CTI CheckPG11Complete STIS CCD Spectroscopic ThroughputsDL33Complete STIS CCD Image and Pointing StabilityTG11Complete STIS FUV MAMA HV RecoveryTW44Complete STIS NUV MAMA HV RecoveryTW4 (+2F) Complete STIS FUV MAMA Dark MeasureCP10 Complete STIS NUV Dark MonitorCP42(+3F)20+52Complete STIS FUV Optical Format VerificationWZ22Complete STIS NUV Optical Format VerificationWZ2 (+2F) Complete STIS FUV MAMA Spectroscopic QualityTG11Complete STIS NUV MAMA Spectroscopic QualityTG11Complete STIS MAMA Spectroscopic ThroughputsDL33Analysis being finalized STIS MAMA Image StabilityTG22Complete

STIS Cycle 17 Calibration Analysis leads assigned for all programs –New leads will also track execution Most Calibration Programs have started –Routine dark monitors have begun Routine delivery of weekly bias and dark reference files –Automated Bias & Dark Pipeline still under work –P-flat data collection has begun SMOV plan deferred this calibration to cycle 17 –Data being combined with SMOV results to improve calibration Cycle 17 data especially important for CTE calibration

STIS Calibration Plan PropIDSTIS SMOV Program TitleAnalysis LeadStart Date 11843CCD Performance MonitorVD01-Sep /11845CCD Dark Monitor (part 1 & 2)MW03-Aug /11847CCD Bias Monitor (part 1 & 2)MW03-Aug CCD Read-noise MonitorVD10-Sep CCD Hot-pixel AnnealingMW23-Jul CCD Spectroscopic FlatsSN10-Aug CCD Imaging FlatsSN27-Aug CCD Spectroscopic DispersionIP20-Aug CCD Sparse Field CTE InternalVD03-Jul CCD Full Field SensitivityVDJan-Mar, Slit Wheel RepeatabilityWZ17-Aug CCD Spectroscopic Sensitivity MonitorRO10-Aug MAMA Dispersion SolutionsIP20-Aug MAMA Full Field SensitivityVDMay, MAMA Sensitivity and Focus MonitorRO03-Sep MAMA Dark MonitorWZ09-Sep MAMA Fold DistributionTWNov, MAMA FUV FlatsTA17-Aug MAMA NUV FlatsTA17-Aug MAMA Anomalous RecoveryTWcontingency 11865COS Flux StandardRBOct, Echelle Grating Blaze Function Zero PointsPGNov, JWST Calibration from a Consistent Absolute Calibration of Spitzer & Hubble RBOct, Sep 2010

STIS CCD Status Dark current, read-noise, and CTE measured Read noise slightly greater than pre-repair –Gain = 1 was 5.3 now 5.8 e - –Gain = 4 was 7.8 now 8.3 e - Observed charge Transfer Efficiency (CTE) in 2009 close to extrapolation of old trend (CTI = 1 - CTE). –CTE losses becoming very large for faint sources

STIS CCD Status - cont Current pipeline CTE algorithm assumes constant “spurious charge” over detector at a given time –Can get better CTE correction if this allowed to vary over detector –This will require modest changes to CALSTIS –For now will use compromise value with old algorithm

CCD Dark Current Behavior Median CCD dark current in 2009 slightly above extrapolated trend from 2004 CCD Dark shows increasing spatial dependence over time –about 40% lower near row 900 as compared to center of chip!

CCD Sensitivity Changes

Advantages of E1 position For many years, we have had defined “E1” positions for CCD near row 900 of STIS long slit –Closer to default readout amplifier –Reduced CTI losses –Reduced effective dark current –Less contamination by CTE tails of CR & hot pixels While we have advertised advantages of E1 position for years in IHB and other documentation, ETC does not distinguish between center and E1 posistion –GO need to manually estimate CTE losses Re-emphasize importance of using E1 position to GOs For cycle 19 ETC, should include variations in dark current & CTE as function of slit position

NUV dark update Post SM4 NUV dark current (black dots) much higher than expected –model as “expected dark” + “something extra” Model as the “expected dark” (orange curve below) declining according to old behavior + an extra component Ae -(  E/T) e -t/  “extra” term appears to have stronger T dependence (  E ≈ 1.8 eV vs 1.5 eV) Plot below compares different e-folding times for extra component   =100 d (red) &  = ∞ (blue)