1. STIS Status Report
Kailash C. Sahu
Apr 18, 2002
TIPS

2. OUTLINE STIS Time Dependent Sensitivity Correction
Sensitivities after SM3B
Echelle Blaze Shift Correction
Improved NUV-MAMA Darks
Phase-II Proposal Reviews

3. Time Dependent Sensitivity Correction
Symptoms
STIS sensitivities are found to slowly change with time
Change is as much as 10% in the last 5 years for some modes
This depends on the detector, and also has a wavelength dependence
The change is not always monotonic in time
Changes in L and M-modes are similar

4. Time Dependent Sensitivity Correction
Time dependence can be corrected by applying a wavelength dependent correction in linear segments of time ( Stys and Walborn).
Algorithm developed by Busko, Hodge, Sahu, Valenti (and the pipeline group)
Implemented in CALSTIS and tested
Residual less than ~2%
Ready to be implemented in the pipeline calibrations.

5. Time Dependent Sensitivity Correction
4/14/2002
4/16/2002
4/16/2002

6. Sensitivities after SM3B
OBSERVATIONS
Sensitivity measurements were taken on April 3 for G230LB, G430L and G750L modes (CCD modes)
On April 14 and April 16 for G140L
On April 16 for G230L
RESULTS
G140L: 1.8% higher on 14th April, but 0.3% higher on 16th April
G230L: Consistent with extrapolated sensitivity.
G750L: -0.6 ± 1.0% (compared to a single measurement 6 months earlier)
G430L: +0.1 ± 1.0%
G230LB: -0.8 ± 1.0%
SUMMARY
All measurements are consistent with the expectations.

7. Echelle Blaze Shift Correction

8. Echelle Blaze Shift Correction
Symptoms
Redundant flux information at ends of echelle orders
Flux discrepancies as large as 10% (see example)
Flux errors correlate with time and monthly offset in X
Grating angle affects wavelength and blaze differently
First Order Correction
Algorithm developed by Don Lindler (calibration outsourcing)
Measured blaze shifts for 600+ datasets (primary cenwaves)
Linear fit of blaze shift vs. time and offsets in X and Y
Fit coefficients added to new columns in _pht reference file
Calstis enhanced by Ivo Busko; tested by Jeff Valenti
Blaze shift estimated from coefficients; good but not perfect
Data may be reprocessed by hand using arbitrary blaze shift
Still need to add support for secondary wavelength settings

9. Improved NUV-MAMA Darks
Changes in the mean operating temperature of the NUV-MAMA causes dark current to deviate from the scaling law used.
Time and temperature dependent correction algorithm was developed by Charles Proffitt
Implemented in CALSTIS with an option to scale the dark to a user-input value (Busko)
Ready to be implemented in the pipeline

10. Phase-II Proposal Reviews
Instrument review of ~2/3rd of the proposals have been completed.
A majority of the remaining are due to PI input, and TOO proposals which cannot be reviewed at this moment.
There are > 500 snapshot observations with MAMA (many of which are for imaging). BOP checking of these observations are time-consuming, and will clearly need more time for completion of the review.