+----------------------------------------------------------+ | NICMOS | STScI Analysis Newsletter | 07 September 2007 +----------------------------------------------------------+ Visit the NICMOS web site http://www.stsci.edu/hst/nicmos "New in the Last 45 Days" for all new information about NICMOS. CONTENTS: -NICMOS Safing and Recovery -A new Instrument Science Report regarding NICMOS Time Dependent Flat-fields -A new Instrument Science Report regarding NICMOS Focus Update -A new Instrument Science Report regarding NICMOS Cycle 15 Baseline Calibration Plans -A new Instrument Science Report regarding Corrections to a Subset of NICMOS Parallel Aperture Locations +----------------------------------------------------------+ NICMOS Safing and Recovery NICMOS entered safe mode on Saturday, September 1, 2007 at 10:58 PM EDT (Day 245, 02:58 UTC), triggered by an apparent Analog/Digital FIFO read failure of internal engineering status by the Control Section flight software of the NICMOS main computer. The most likely candidate for the cause of this error was a transient single event upset affecting either the special engineering data buffer, a CPU register, or a memory location. This event occurred during orbit day outside the South Atlantic Anomaly. HST was in two-gyro mode following the successful recovery from the failure of Gyro #2 on the previous day, which appears unrelated to the NICMOS safing, and NICMOS was not carrying out any observations at the time. All remaining NICMOS observations for the week of September 3, 2007 were removed from the calendar until the instrument could be recovered. All other NICMOS telemetry diagnostics remained nominal up to the point at which the error occured, and there is no indication of any failure in the NICMOS electronics or mechanisms. The NCS was also not affected and continued operating nominally during the event. Similar single event upsets have been observed in the past on other instruments as transient events. As no credible risk to the instrument could be identified, HST Project proceeded with the recovery procedure. NICMOS was successfully transitioned from safe to SAA operate on September 4, 2007 at 1:10 PM EDT (Day 247, 17:10 UTC), and by September 6, 2007 all three internal buffer boxes had reached their nominal operating temperatures. No reoccurence of the error has been observed. NICMOS science observations are scheduled to resume as normal during the week starting September 10, 2007. +----------------------------------------------------------+ NICMOS ISR 2007-002: NICMOS Time Dependent Flat-fields T. Dahlen, H. McLaughlin and R. de Jong http://www.stsci.edu/hst/nicmos/documents/isrs/isr_2007_002.pdf We use data obtained during the NICMOS flat-field monitoring 2002-2007 to derive a set of time dependent flat-fields. These epoch flat-fields are compared to the current pipeline flat-fields and differences are quantified. Our results are consistent with a decrease in DQE over the five-year period on the order of one per cent. We also find that the spatial structure of the flat-fields change with time. The reasons for these changes are not fully known, but we note that the changes are consistent with a change in detector temperature with time. The order of this effect is generally less than one percent. +----------------------------------------------------------+ NICMOS ISR 2007-003: NICMOS Focus Update H. McLaughlin and T. Wiklind http://www.stsci.edu/hst/nicmos/documents/isrs/isr_2007_003.pdf This ISR addresses a number of improvements in the way the NICMOS focus is monitored. It provides a detailed explanation of those changes and a step by step description of the new procedure. The ISR also highlights the results of the focus checks after the January 2007 HST safing event, which caused the NICMOS cooling system (NCS) anomalous shutdown in February of 2007. +----------------------------------------------------------+ NICMOS ISR 2007-004: NICMOS Cycle 15 Baseline Calibration Plans N. Pirzkal, E. Barker, L. Bergeron, R. Bohlin, T. Dahlen, R. De Jong, A. M. Koekemoer, H. McLaughlin, B. Shaw, T. Wiklind http://www.stsci.edu/hst/nicmos/documents/isrs/isr_2007_004.pdf This document summarizes the NICMOS Calibration Plans for Cycle 15. The monitoring programs from the previous Cycle 13 and 14 are carried out in Cycle 15. Additional calibration is included in order to improve the accuracy of previously archived NICMOS data. +----------------------------------------------------------+ NICMOS TIR 2007-001: Corrections to a Subset of NICMOS Parallel Aperture Locations M. Lallo, C. Cox, I. Dashevsky, A. M. Koekemoer While delivering recently required new SIAF entries representing defocused NICMOS apertures, we discovered incorrect values in existence for a specific set of NICMOS parallel camera positions. We investigated and understood the cause, determined the correct values, proposed a fix, both retroactive and for the future then delivered the corrected data to operations. The error, which was extant for at least five years (since cryo-cooler operations), was unnoticed by GOs, the IDT, and the STScI due to the fact that it affected only the astrometry of certain NICMOS camera FOVs when they were used as parallel with a PAM setting that placed them significantly out of focus (~0.5 micron rms wavefront error). +----------------------------------------------------------+ For more detailed information and updates, please consult the NICMOS webpages: http://www.stsci.edu/hst/nicmos +----------------------------------------------------------+ | Help: help@stsci.edu +----------------------------------------------------------+ | To subscribe or unsubscribe to the STAN, send a message | to majordomo@stsci.edu with the subject line blank and | the following in the body: [un]subscribe nicmos_news +----------------------------------------------------------+ | The Space Telescope Science Institute is operated by the | Association of Universities for Research in Astronomy, | Inc., under NASA contract NAS5-26555. +----------------------------------------------------------+
