1. STScI TIPS/JIM 18 September 2008 NICMOS/NCS Anomaly and Status Anton Koekemoer 1 NICMOS/NCS Anomaly and Status Timeline overview: NICMOS/NCS was commanded to shutdown on Sep 10 to prepare for NSSC-I Subsequent recovery on Sep 11 lasted ~ 6 hours before safing 3 subsequent retries safed Safings typically indicated above-average current drawn by the circulator motor Current status / prognosis Possibly due to water ice/contaminant interfering with circulator pump Other anomalous telemetry confirms likelihood of contaminants No evidence of any permanent damage to the mechanical system Plans forward Decision by HST-P to allow system to warm up, thaw contaminants Cooldown would take a few weeks, similar to SMOV3B Given SM4 October launch date, remainder of Cyc 15 & 16 NICMOS will execute in Cycle 17

2. STScI TIPS/JIM 18 September 2008 NICMOS/NCS Anomaly and Status Anton Koekemoer 2 Initial NCC restart timeline 255/01:14:05 –Circulator On (1200 Hz) 255/01:27:37 –Compressor On (5000 Hz) 255/02:33:02 –CPL Control 255/003:07:56 –CPL Operate/Compressor Ramp (6000 Hz) 255/03:10:39 –PID Operate (7043 rps + Surge effects) 255/05:44:00 –Exit FSW-defined Surge (7330 rps) 255/07:57:47 –Safing indicating overspeed limit for Circulator pump –No apparent deviation of the Circulator differential pressure (MNCIDFPR) or the Circulator frequency (MNCIIFRQ)

3. STScI TIPS/JIM 18 September 2008 NICMOS/NCS Anomaly and Status Anton Koekemoer 3

4. STScI TIPS/JIM 18 September 2008 NICMOS/NCS Anomaly and Status Anton Koekemoer 4

5. STScI TIPS/JIM 18 September 2008 NICMOS/NCS Anomaly and Status Anton Koekemoer 5 2008 restart - current and pressure diff.

6. STScI TIPS/JIM 18 September 2008 NICMOS/NCS Anomaly and Status Anton Koekemoer 6 2007 restart - current and pressure diff.

7. STScI TIPS/JIM 18 September 2008 NICMOS/NCS Anomaly and Status Anton Koekemoer 7 2003 Restart - current and pressure diff.

8. STScI TIPS/JIM 18 September 2008 NICMOS/NCS Anomaly and Status Anton Koekemoer 8 Differences between 2008 vs 2007/2003 On-Orbit History 2002: Initial start-up after installation during SM3B 2002: NCC Restart following Turboalternator (TBA) failure in SMOV 2003: Restart following DOY 213 SEU corrupting the Circulator commanded voltage (NCC only) 2007: Restart following 027/2007 NCC Safing event due to Total Pressure Sensor (TPS) limit violation (NCC only) Comparison: Absolute temperature of circulator housing and NICMOS return higher during prior restarts dT between circulator housing and NICMOS return higher this time Circulator current higher during first hour of recent restart Circulator restart transient appears similar during initial restart but current is 1.5X after 20 sec At circulator housing temperatures of nominally 120 K, the circulator current was higher by 2X during recent restart Anomalous current event noted during recent restart prior to shutdown

9. STScI TIPS/JIM 18 September 2008 NICMOS/NCS Anomaly and Status Anton Koekemoer 9 Contaminant Possibilities Scenario: Ice particle is dislodged during initial cool down event. –May be related to the short duration of the stoppage. Particle runs through circulator turbine. Higher mechanical load leads to mismatch in phase angle between back- EMF and drive signal. –Causes large rise in Circulator current. –Slight drop in Circulator voltage consistent with large draw, and is in opposite phase. –Current is a good indicator of motor torque. Perturbed rotor triggers speed sensor to have additional switches per revolution, and appears as an erratic increase in speed. Circulator does NOT drop out of sync. Creare has study on the size range –10 u to 1 mm size range No good theory on how ice formed Cannot be explained by change in temperature and partial pressure.

10. STScI TIPS/JIM 18 September 2008 NICMOS/NCS Anomaly and Status Anton Koekemoer 10 Subsequent restart attempts 09/14/2008 20:00 Circulator current threshold was lowered from 381 to 130 mA, to avoid running the system at high current for prolonger period of time Safed almost immediately due to current threshold limit exceeded 09/15/2008 16:00 Circulator current threshold was raised from 130 to 150 mA Safed this time due to circulator speed violation limit exceeded 09/15/2008 20:00 Circulator speed limit threshold was raised Ran for about 20 - 25 minutes Safed due to likely current limit exceeded (telemetry was lost during the final minutes)

11. STScI TIPS/JIM 18 September 2008 NICMOS/NCS Anomaly and Status Anton Koekemoer 11

12. STScI TIPS/JIM 18 September 2008 NICMOS/NCS Anomaly and Status Anton Koekemoer 12

13. STScI TIPS/JIM 18 September 2008 NICMOS/NCS Anomaly and Status Anton Koekemoer 13 NCS System with Temperatures & Parasitics T1 MNCOINLT T3 MNAFTCOT T4 MNPTAILT T6 MNPLINTT T7 MNPNCOLT T9 MNRNCILT Trej MNH TREE JT Flexline Inlet 0.19 W Outlet 0.26 W Tested 5.105 W Bayonets In 0.78 W Out 1.69 W Supp Brkt 0.04 watts Analysis 1.29 W Total 6.395 W Rigid Tubes Inlet 0.08 W Outlet 0.065 W Total parasitics expected to be lower at BOL

14. STScI TIPS/JIM 18 September 2008 NICMOS/NCS Anomaly and Status Anton Koekemoer 14 NICMOS Dewar with Temperatures and Parasitics Cryo Valve Heaters (2) TEC Radiator Cryovalves 2.22 watts (includes htrs) Internal 0.40 watts Load to tank 0.67 watts Review of MEB/BB powerdown shows parasitc change is consistent with model predictions

15. STScI TIPS/JIM 18 September 2008 NICMOS/NCS Anomaly and Status Anton Koekemoer 15 Previous NICMOS Cool-downs Cool–down of the NICMOS dewar (from 3 previous NCS start-ups) Red curve = weighted average of the Ne inlet and outlet temperatures Mar 2002 SMOV3b Aug 2003Jan 2007

16. STScI TIPS/JIM 18 September 2008 NICMOS/NCS Anomaly and Status Anton Koekemoer 16 Current / Forward Plans NICMOS / NCS: Continue warming up to ~270 K, enable contaminants to thaw Keep TECs running to dewar - essentially retain system in as similar state as possible to post-cryogen / pre-SMOV3B Keep to original SM4 plan to commence cooldown after SM4 SMOV & Calibration programs: May need to defer start of NICMOS SMOV4 by a few weeks, since cooldown would likely take longer than previously planned Likely augment NICMOS SMOV4 plan to include more comprehensive filter wheel tests, PAM/FOM tests, focus (similar to SMOV3B) Post-SMOV4 Cycle 17 calibration may need additional observations if there are changes in the properties of the system GO programs: All remaining Cycle 15 and 16 programs are being retained and will execute after SMOV4 along with the Cycle 17 NICMOS program