STIS Status

1. STIS Status TIPS July 16, 2009

2. STIS Status • STIS MIE anomaly • What is known • STIS CCD status before the anomaly • STIS MAMA SMOV status

3. STIS MIE Anomaly • STIS currently suspended • Original suspend (day 187): Main STIS CS computer unable to get timecode update from MIE (MAMA Interface Electronics) that was needed to populate the header of a CCD exposure. • Originally suspected that single event upset had hung up the MIE 486. • 2nd suspend (day 190): Suspended while attempting to copy MIE memory to CS. Done before full reset in attempt to preserve MIE memory • Theorized that problem with MIE dump was caused by lack of full reset, and hoped a full reset would clear the problem. • About 1/2 of MIE memory was successfully copied. • 3rd suspend (191): Did full reset and successfully recovered STIS to operate, but suspended while attempting to copy MIE memory to CS. • MIE copy to CS seems to have succeeded, but still suspended • Recovery included successful queries of MIE for time code update (I.e., the original problem from day 187 did not recur). • Observed events suggest transient failure on MIE FIFO Flags interface between CS and MIE?

4. STIS MIE Anomaly - cont • What we know: • The three anomalies occurred during three different circumstances and have three different and - in some aspects - inconsistent signatures • Observed events suggest transient failure on MIE FIFO Flags interface between CS and MIE • Investigation is continuing • Perhaps MIE dump problem is separate from original time code update problem? • STIS still suspended • Hope to allow resumption of CCD operations soon, while analysis continues. • See if original anomaly reoccurs. • CCD observations could, in principle work around MIE problems • Since anomalies are not yet understood, implications for MAMA observations are not yet known

5. STIS CCD Read Noise • STIS CCD read noise slightly increased from ~ 5.4 e- in 2004 to ~ 5.7 e- now • Side 2 read-noise includes ~ 1 DN of semi-coherent 17 kHz pattern noise • This pattern noise appears to be unchanged after SM4

6. STIS CCD Dark Current • CCD housing temperature (OCCDHT) surrogate for CCD chip T • For comparison these plots scale darks to housing temperature of 18 C • Dark rate increases by 7%/degree of housing temperature • 2009 aft-shroud hotter than 2004 • When MAMAs on, OCCDHT 22-25 C • With MAMAs off, OCCDHT 16-18 C • RN between 0.009 and 0.013 e-/s, fluctuating with temperature

7. TDS & CTE effects • Standard monitor target AGK+81o266 (*’s) shows large scatter at low flux levels (right panel), even in 2004 - correlates with T • Need to separate T dependence of CTE before deriving final throughput estimates

8. CTE extrapolated to zero background as a function of flux level • 2009 points are at colder T than older data • Expect reduced CTE losses at lower T

9. MAMA SMOV Status • FUV MAMA • FUV MAMA HV ramped to full values • Fold test & flat look as expected • Dark current perhaps lower than expected • NUV MAMA • Initial steps of NUV MAMA HV recovery completed • Have not yet ramped NUV HV to level where tube generates real counts. • Still need to do initial internal lamp exposures and external exposures with both MAMAs • Once MAMAs cleared for operations, most SMOV activities for either or both could be completed in a week if time available.