STIS Status

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

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

3. 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 11857 • Detailed writeups still pending for most activities

5. 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

6. STIS Calibration Plan

7. 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

8. 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

9. 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!

10. CCD Sensitivity Changes

11. 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

12. 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)