+----------------------------------------------------------+ | NICMOS | STScI Analysis Newsletter | NICMOS STAN 30 | October 2003 +----------------------------------------------------------+ Visit the NICMOS web site http://www.stsci.edu/instruments/nicmos "New in the Last 45 Days" for all new information about NICMOS. CONTENTS (Optional): -NICMOS Recovered from Safe Mode -NICMOS Mini-Check Out -filter wheel test -focus monitoring -coma check -NICMOS Coronagraphic Observations -NICMOS Temperature Table -NICMOS Polarimetry Calibration -NICMOS Focus Monitor -NICMOS post-SAA Darks -Recent NICMOS Publications +----------------------------------------------------------+ http://www.stsci.edu/hst/nicmos NICMOS Recovered from Safe Mode K. Noll On Saturday August 2, 2003, the NICMOS Cooling System (NCS) was safed due to an input voltage reaching an out of limits point. This resulted in a shutdown of all the cooler systems. The NICMOS was safed (2003.214:21:56:43 UT) using real time commanding in order to reduce the heat load within NICMOS. The HST was in the South Atlantic Anomaly (SAA) at the time of the safing. Subsequent investigation indicated that a high energy particle caused an upset in the digital register used to command the input voltage, causing it to jump by 256 units. This then put the voltage out of range, and caused the safing. There were no indications in the engineering telemetry of any mechanical problem or permanent electronic failure. On August 7, 2003, the NCS circulator and compressor were successfully restarted. Operation was nominal and the circulator inverter input voltage, which caused the safing, was at 6.06 V within normal range of the nominal value of 6.2 V. Active temperature control was achieved two days later when the temperature set point of 77.1 K was reached (weighted average of the neon inlet and outlet temperatures). The NICMOS was recovered from safe mode on August 14, 2003. Science observations resumed on August 21, 2003. +----------------------------------------------------------+ http://www.stsci.edu/hst/nicmos NICMOS Mini-Check Out K. Noll, S. Arribas, E. Bergeron, S. Malhotra, B. Mobasher, E. Roye, A. Schultz, M. Sosey, T. Wiklind, C. Xu, and G. Schneider. Following recovery from Safe Mode, each of the NICMOS filter wheels were exercised and flat field observations (lamp-off and lamp-on) were obtained (program ID: 10062). Voltages and currents were nominal during movement of the filter wheels. Inspection of the flat field and dark observations obtained in support of the filter wheel test confirmed motion of the filter wheels to the commanded filter positions and back to blank. No changes in debris on detectors (grot) were noted. Flat field filter count rates were as expected. No change. Test program 10063, "NICMOS Focus and PAM Grid Tilt Tests" executed on August 19, 2003. The purpose of this program was to measure the focus and coma to determine if they had changed, and if necessary, to update them. The standard focus target field, star cluster NGC3603, was observed with NIC1 and NIC2. A 17-point focus sweep was executed in each camera, a ± 8mm movement of the PAM about its mechanical zero point. The focus was determined to be nominal in both cameras. No change. Since the focus for NIC3 tracks the focus in NIC1 and NIC2, no change is expected and the subsequent NIC3 observations withdrawn. The observed coma was negligible, indicating that the PAM tilt position had not changed. Contingency visits were not needed and withdrawn. +----------------------------------------------------------+ http://www.stsci.edu/hst/nicmos NICMOS Coronagraphic Observations G. Schneider and A. Schultz NICMOS Cycle 12 Camera 2 coronagraphic science observations started on August 26, 2003 with the observations of the faint white dwarf GJ 3182 (mv=15.32). Due to the faintness of the target, the flight software (FSW) acquired a bad pixel even though the counts in the image of the target were sufficient to acquire the target. A brighter target would not have had this problem. Bad pixels were identified and the NICMOS Target Acquisition Pixel Gain Table onboard HST was updated on September 12, 2003. This pixel table, used for all Mode-2 coronagraphic acquisitions, is specified for targets of magnitude J ~4 to J ~18. Subsequent Mode-2 acquisitions of faint targets have been successful. +----------------------------------------------------------+ http://www.stsci.edu/hst/nicmos NICMOS Temperature Table A. Schultz As an aid to NICMOS users, values of nine NICMOS Cooling System (NCS) mnemonics and five NICMOS temperature sensors are extracted from the engineering telemetry and bundled together into a FITS table called the NICMOS Temperature Table. The information in the table may be used in calibration or temperature monitoring. A table will be created for each NICMOS observation and will have an extension of epc (ipppssoot_epc.fits). Currently, tables are created and stored in OPUS until ingestion into the HST Archive. NICMOS observers may request tables from OPUS in support of their observations. Information about the table can be found in NICMOS Instrument Science Report (ISR) titled: "NICMOS Temperature Table," NICMOS-ISR-2003-008 +----------------------------------------------------------+ http://www.stsci.edu/hst/nicmos NICMOS Polarimetry Calibration D. Hines Cycle 11 polarimetry calibrations have been completed for the NIC1 and NIC2 polarizers (program ID: 9644). The polarization t(k)-coefficients, as explained in the NICMOS explained in the NICMOS Data Handbook and in Hines, Schmidt & Schneider (2000, PASP, 112, 983), have changed slightly since Cycles 7 & 7N. All other fundamental polarizer coefficients remain unchanged. Quantities derived from the t-coefficients, such as the A, B and C terms in the polarization reduction equation, should be regenerated using the new t-values. This exercise has been performed in the new NICMOS manuals and is available from the NICMOS web site. The new polarimetry calibrations should be used for all NICMOS polarimetry data obtained after the NCS installation (March 2002). Using these revised coefficients, NICMOS is capable of producing imaging polarimetry results with accuracies of 1-2% (in percentage polarization), comparable with its pre-NCS capabilities. The new coefficients will be incorporated by D. Hines and B. Stobie of the NICMOS IDT into the IDL polarimetry package called "Polarize." This updated (but unsupported) package will be available from the NICMOS public software site and will be delivered to STScI. +----------------------------------------------------------+ http://www.stsci.edu/hst/nicmos/performance/focus/ post-ncs_focus_update.html NICMOS Focus Monitor E. Roye and T. Wiklind The results of the September 2003 NIC1 and NIC2 focus sweep data indicate the focus is nominal, within 0.1 mm of the current setting. There was no NIC3 focus sweep this month. The NIC3 focus sweep is scheduled for mid-October. The latest focus plots have been posted on the NICMOS web site. +----------------------------------------------------------+ http://www.stsci.edu/hst/nicmos/tools NICMOS post-SAA Darks E. Bergeron and M. Dickinson Latent or "persistent" images of cosmic rays hits following HST transits of the South Atlantic Anomaly (SAA) can significantly increase the noise in subsequent NICMOS science images. A map of the persistent signal can be made from the pair of post-SAA DARK exposures which are obtained immediately following exit of the SAA. This map can then be used to subtract the latent "persistent" signal from impacted images obtained in that orbit, thereby recovering much of the original S/N. Information describing the problem and an algorithm to remove the persistent signal can be found in NICMOS Instrument Science Report (ISR) titled: "Removal of Cosmic Ray Persistence From Science Data using the Post-SAA Darks," The algorithm has been coded in an IDL routine called "saa_clean.pro" which is available upon request from the STScI NICMOS web page. The IDL routine is being converted into a stand-alone STSDAS task for release at a future date. +----------------------------------------------------------+ | Recent NICMOS Publications +----------------------------------------------------------+ There are currently 53 NICMOS refereed publications for 2003. Many NICMOS observations were retrieved from the HST Archive in support of ground-based and HST observing programs. Some publications reported new NICMOS observations as follow up observations to existing programs. +----------------------------------------------------------+ | 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. +----------------------------------------------------------+
