+----------------------------------------------------------+ | NICMOS | STScI Analysis Newsletter | NICMOS STAN 34 | April 2005 +----------------------------------------------------------+ Visit the NICMOS web site http://www.stsci.edu/hst/nicmos "New in the Last 45 Days" for all new information about NICMOS. CONTENTS (Optional): -HST Cycle 14 Phase II Submission Deadline -Release of APT 14.2 for HST Cycle 14 -New SPARS MULTIACCUM Timing Sequences -Two Gyro Mode Guiding Test -Time-Limited Non-Linear Response of NICMOS at Low Count Rates -October 2005 Calibration Workshop -HST 700,000 Observation +----------------------------------------------------------+ http://www.stsci.edu/hst/programs HST Cycle 14 Phase II Submission Deadline Cycle 14 Phase II Submission Deadline is May 13, 2005. Cycle 14 observing starts in July 2005. Documentation and tools necessary to develop, submit, and monitor your HST Phase II proposal can be found on the Cycle 14 Phase II web page. +----------------------------------------------------------+ http://apt.stsci.edu/ Release of APT 14.2 for HST Cycle 14 APT Team APT 14.2 was released on April 7, 2005 in support of Cycle 14 Phase II proposal development. An APT "Roadmap", a step-by-step guide to writing a Phase II proposal, is available at http://apt.stsci.edu/help/roadmap.html Observers who need to refine a Cycle 13 proposal should contact their Program Coordinator (PC) to determine which version of APT they should use. APT 14.2 is available for download from the APT web page. +----------------------------------------------------------+ http://www.stsci.edu/hst/nicmos New SPARS MULTIACCUM Timing Sequences NICMOS Team Four MIF MULTIACCUM timing sequences (MIF512, MIF1024, MIF2048, and MIF3072) have been replaced by four new SPARS MULTIACCUM timing sequences. The four new timing sequences are SPARS4, SPARS16, SPARS32, and SPARS128. Each timing sequence has two rapid reads at the beginning and end with evenly spaced read outs of 4s, 16s, 32s, and 128s, respectively. The new SPARS sequences can be most useful for fields with faint sources; i.e., galaxies, nebulae, and faint star clusters. +----------------------------------------------------------+ http://www.stsci.edu/hst/nicmos Two Gyro Mode Guiding Test NICMOS Team The Two Gyro Mode test was executed on February 21-23, 2005. The rate information from two gyros and one Fine Guidance Sensor (FGS) at 40 Hz was input into the attitude control law of the Pointing Control System (PCS). A series of NICMOS exposures were obtained to measure any possible guiding anomalies (dither test), to measure the PSF variability, and the performance of the NICMOS coronagraphy. The actual on-orbit Two Gyro Mode average jitter (60 sec RMS) for the gyro pair was ~6.2 mas with a maximum jitter of ~7.3 mas. The the jitter during the Two Gyro Mode test was comparable to the three gyro mode jitter. Dithering was successful indicating no affects due to Two Gyro Mode and no measurable differences were found when comparing the PSF FWHM for point sources obtained under Two Gyro Mode or three gyro mode guiding. Rolling the telescope within the same visibility period for coronagraphy will not be allowed under Two Gyro Mode. A roll roll of the telescope between adjacent orbits was performed for the the coronagraphic test. The observed coronagraphic performance was essentially unaffected at 1.1 micron while there was a slight decline at 1.6 micron. At r=10 pixels, the coronagraphic suppression factor is 3 compared to direct imaging, while it is a factor of 4 in three gyro mode. The coronagraphic gains with Two Gyro Mode operations were still substantial compared to direct imaging (Schultz et al. 2005 ISR-2005-001). +----------------------------------------------------------+ http://www.stsci.edu/hst/nicmos/performance/anomalies/charge-trapping.html Time-Limited Non-Linear Response of NICMOS at Low Count Rates NICMOS Team A study designed to use the NICMOS grisms to extend faint calibration standards beyond 1 micron found a previously unseen effect. When compared to STIS and ACS in portions of the spectrum where these instruments overlap in coverage with NICMOS, the ratios of standards of different brightnesses are found to differ systematically (Bohlin et al. (2005 ISR-2005-002). The effect is most pronounced at shorter wavelengths and disappears at wavelengths longer than 1.6 micron. However, the quantitative correction formula for the observed non-linearity of the grism spectra may not be applicable to point source photometry. Comparison of photometry of faint sources in the UDF with ground-based observations of the same sources failed to find significant differences that would indicate a general problem with NICMOS photometry (Mobasher et al. 2005 ISR-2005-003). In a separate study by A. Riess (unpub), examination of intermediate reads in both the NICMOS grism data used by Bohlin et al. and in other photometric observations shows an apparent deficit in count rate at shorter exposure times. The functional form of the trend is approximately exponential with a time constant of about 150 seconds. This is the same function that describes the release of charge in persistent images and suggests that charge traps may be responsible for the phenomenon. Integrations that begin with charge traps unfilled will have a deficit in counts until the filling and emptying of charge traps comes to equilibrium. This provides a natural explanation for the observed effect in the NICMOS grism observations used by Bohlin et al.. Most observations obtained for science will not be strongly affected by this effect either because the integration times are significantly longer than the 150 second e-fold time or because the source count rates are sufficiently high that the fraction of charge lost to traps is negligible. Scientific observations at shorter wavelengths made with relatively short integrations that compare bright and faint sources obtained in the same exposure will be most vulnerable. Examination of background-subtracted intermediate reads from the ima file should be done by anyone concerned that their observations may be measurably affected. The NICMOS group will establish a dedicated link on the STScI NICMOS Instrument page that will give all the details of this phenomenon and will provide updated advice for cycle 14 Phase 2 proposals. +----------------------------------------------------------+ http://www.stsci.edu/resources/ October 2005 Calibration Workshop STScI will host an HST Calibration workshop Oct 26-29, 2005. The goal of the workshop is to foster the sharing of information and techniques between observers, instrument developers, and instrument support teams. We invite NICMOS observers to suggest calibration or observing topics to be discussed at the workshop. +----------------------------------------------------------+ HST 700,000 Observation OPUS Team On April 10, 2005, around 6:00pm EDT, HST took its 700,000th exposure since launch of HST in April 1990. This total includes internal calibration exposures as well as targeted observations using all nine Science Instruments that have been or are still onboard HST (HSP, WFPC-1, FOS, GHRS, FOC, WFPC-2, STIS, NICMOS, ACS). The 700,000th Hubble exposure used the NICMOS for a parallel observation in the Orion Nebula while the ACS was exposing on a specific region under proposal 10246, "The HST survey of the Orion Nebula Cluster", whose PI is Massimo Robberto of STScI and ESA. This is a Treasury Program to perform a definitive study of the Orion Nebula Cluster, the Rosetta stone of star formation, with unprecedented sensitivity, spatial resolution, and simultaneous spectral coverage over a field centered on the Trapezium stars. In addition, 30,000 astrometric science datasets using the Fine Guidance Sensors have been processed since 1990 from the engineering telemetry. The 30,000th astrometry observation executed on April 4, 2005, for GO proposal 10107 by Douglas Gies (Georgia State U. Research Foundation), "The Masses of the O-type Binary 15 Monocerotis." +----------------------------------------------------------+ | Recent NICMOS Publications +----------------------------------------------------------+ There are 25 NICMOS refereed publications for 2005. Many NICMOS observations were retrieved from the HST Archive in support of ground-based and HST observing programs. Some publications reported new NICMOS observations while others reported follow up observations to existing programs. A few publications of note are listed below: Apai, D., et al. 2005, "HST/NICMOS Observations of a Proto-brown Dwarf Candidate," A&A, 433, L33-L36 Colbert, J.W., et al. 2005, "Near-Infrared Properties of Faint X-ray Sources from NICMOS Imaging in the Chandra Deep Fields," ApJ, 621, 587-595 Colina, L., Arribas, S., Monreal-Ibero, A. 2005,"Kinematics of Low-z Ultraluminous Infrared Galaxies and Implications for Dynamical Mass Derivations in High-z Star-Forming Galaxies," ApJ, 621, 725-737 Figer, D.F. 2005, "An Upper Limit to the Masses of Stars," Nature, 434, 192-194 Sahai, R., Sanchez Contreas, C., Morris, M. 2005, "A Starfish Preplanetary Nebula: IRAS 19024+0044," ApJ, 620, 948-960 Ueta, T., Murakawa, K., Meixner, M. 2005, "Hubble Space Telescope NICMOS Imaging Polarimetry of Proto-planetary Nebulae: Probing the Dust Shell Structure via Polarized Light," AJ, 129, 1625-1641 A complete list of NICMOS publications by year can be generated from the STScI Library home web page by clicking the link "HST Biblography" and entering the year and selecting NICMOS: http://sesame.stsci.edu/library.html +----------------------------------------------------------+ | 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. +----------------------------------------------------------+
