Status Report

NASA Hubble Space Telescope Daily Report #4931

By SpaceRef Editor
September 18, 2009
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Continuing to Collect World Class Science

PERIOD COVERED: 5am September 15 – 5am September 16, 2009 (DOY 258/09:00z-259/09:00z)


COS/FUV 11482

FUV Detector Dark

The purpose of this proposal is to measure the FUV detector dark rate by taking long science exposures with no light on the detector. The detector dark rate and spatial distribution of counts will be compared to pre-launch data in order to verify the nominal operation of the detector, and for use in the CalCOS calibration pipeline. Variations of count rate as a function of orbital position will be analyzed to find dependence of dark rate on proximity to the SAA.

This is SMOV Activity COS-24.

COS/FUV 11492

FUV Sensitivity

This activity confirms COS sensitivity versus wavelength over the entire observable spectrum for all FUV gratings and central wavelength settings. Obtain quick look sensitivity visit early in SMOV. Later, after wavelength calibration is verified, perform a precise-centering acquisition and observe an appropriate HST flux standard star (chosen from the HST prime standard and FASTEX lists) with the PSA. (A limited BOA characterization is obtained in Visit 13 using primary standard GD153.) No off aperture- center observations are performed in this activity (see COS32, program 11490, for off- center characterizations). Spectra will be obtained to meet a Poisson S/N criterion of ~30 per sensitivity extraction bin or higher; substantially higher S/N characterization will be utilized in routine Cycle 17 calibration.

COS/FUV 11897

FUV Spectroscopic Sensitivity Monitoring

The purpose of this proposal is to monitor sensitivity in each FUV grating mode to detect any changes due to contamination or other causes.

COS/FUV 11997

FUV Internal/External Wavelength Scale Monitor

This program monitors the offsets between the wavelength scale set by the internal wavecal versus that defined by absorption lines in external targets. This is accomplished by observing two external targets in the SMC: SK191 with G130M and G160M and Cl* NGC 330 ROB B37 with G140L (SK191 is too bright to be observed with G140L). The cenwaves observed in this program are a subset of the ones used during Cycle 17. Observing all cenwaves would require a considerably larger number of orbits. Constraints on scheduling of each target are placed so that each target is observed once every ~2-3 months. Observing the two targets every month would also require a considerably larger number of orbits.


COS-GTO: Atmosphere of a Transiting Planet

COS observations of a transiting planet at different orbital locations will be useful in identifying the chemical content, size, temperature, and flows in the atmosphere of a transiting planet.

FGS 11942

Increasing the Accuracy of HST Astrometry with FGS1R

We propose to observe six exoplanetary system host stars and two planetary nebulae central stars with FGS1R. All objects have been previously observed under proposals GO-09233, -09969, -10989, and -11210. These observations will significantly extend the time baseline, permitting improvements in the determination of proper motion. This systematic motion must be removed to get at the perturbation of interest, either due to exoplanetary companions or the orbital motion of the Earth (parallax). In most cases the perturbation orbits will also improve. We improve either companion mass or PN parallax. For one target, GJ 876, theoretical dynamical modelers have proposed an inclination closer to 50 degrees, while FGS3 measurements indicated an inclination closer to 84 degrees. These new data, once combined with our older FGS3 data, will permit an independent remeasurement of the inclination of the outermost companion, and a re- evaluation of widely used dynamical algorithms.

NIC1/NIC2/NIC3/S/C 11406

NICMOS DC Transfer Function Test

This early activity following the re-activation and re-cooling of NICMOS following SM4 is designed to test the basic operability of the NICMOS HgCdTe photodiode array focal plane detectors without exposure to external stimulating irradiation. This test requires “special commanding” and “non-standard” instrument state transition scheduling. This test is to be executed following NCS cool-down and equilibration of the NICMOS detectors at their anticipated nominal Cycle 17 operating temperatures.

Detector operability and dark functionality will be assessed from executing a bias- voltage ramped series series non-stimulated (dark) multiple non-destructive readout exposures; with the detector bias voltages ramped in 0.1V commanded steps from 0 volts DC to 0.6 volts DC. These data MUST be taken in parallel in all three cameras, and make use of “non- standard” multi-accum sample-sequences, as we will compare these results directly to multiple pre-launch runs of the NICMOS System Test as well as the execution of SM2/NIC 7037 and SM3B/8976.

STIS/CCD 11844

CCD Dark Monitor Part 1

The purpose of this proposal is to monitor the darks for the STIS CCD.

STIS/CCD 11846

CCD Bias Monitor-Part 1

The purpose of this proposal is to monitor the bias in the 1×1, 1×2, 2×1, and 2×2 bin settings at gain=1, and 1×1 at gain = 4, to build up high-S/N superbiases and track the evolution of hot columns.

STIS/MA1/MA2 11857

STIS Cycle 17 MAMA Dark Monitor

This proposal monitors the behavior of the dark current in each of the MAMA detectors.

The basic monitor takes two 1380s ACCUM darks each week with each detector. However, starting Oct 5, pairs are only included for weeks that the LRP has external MAMA observations planned. The weekly pairs of exposures for each detector are linked so that they are taken at opposite ends of the same SAA free interval. This pairing of exposures will make it easier to separate long and short term temporal variability from temperature dependent changes.

For both detectors, additional blocks of exposures are taken once every six months. These are groups of five 1314s FUV-MAMA Time-Tag darks or five 3x315s NUV ACCUM darks distributed over a single SAA-free interval. This will give more information on the brightness of the FUV MAMA dark current as a function of the amount of time that the HV has been on, and for the NUV MAMA will give a better measure of the short term temperature dependence.

WFC3/IR/S/C 11929

IR Dark Current Monitor

Analyses of ground test data showed that dark current signals are more reliably removed from science data using darks taken with the same exposure sequences as the science data, than with a single dark current image scaled by desired exposure time. Therefore, dark current images must be collected using all sample sequences that will be used in science observations. These observations will be used to monitor changes in the dark current of the WFC3-IR channel on a day-to-day basis, and to build calibration dark current ramps for each of the sample sequences to be used by GOs in Cycle 17. For each sample sequence/array size combination, a median ramp will be created and delivered to the calibration database system (CDBS).

WFC3/UVIS 11650

Mutual Orbits, Colors, Masses, and Bulk Densities of 3 Cold Classical Trans-Neptunian Binaries

Many Trans-Neptunian Objects (TNOs) have been found to be binary or multiple systems. As in other astrophysical settings, Trans-Neptunian Binaries (TNBs) offer uniquely valuable information. Their mutual orbits allow the direct determination of their system masses, perhaps the most fundamental physical quantity of any astronomical object. Their frequency of occurrence and dynamical characteristics provide clues to formation conditions and evolution scenarios affecting both the binaries and their single neighbors. Combining masses with sizes, bulk densities can be measured. Densities constrain bulk composition and internal structure, key clues to TNO origins and evolution over time. Several TNB bulk densities have been determined, hinting at interesting trends. But none of them belongs to the Cold Classical sub- population, the one group of TNOs with demonstrably distinct physical characteristics. Two top-priority Spitzer programs will soon observe and measure the sizes of 3 Cold Classical TNBs. This proposal seeks to determine the mutual orbits and thus masses of these systems, enabling computation of their densities.

WFC3/UVIS 11905

WFC3 UVIS CCD Daily Monitor

The behavior of the WFC3 UVIS CCD will be monitored daily with a set of full-frame, four-amp bias and dark frames. A smaller set of 2Kx4K subarray biases are acquired at less frequent intervals throughout the cycle to support subarray science observations. The internals from this proposal, along with those from the anneal procedure (Proposal 11909), will be used to generate the necessary superbias and superdark reference files for the calibration pipeline (CDBS).

WFC3/UVIS 11908

Cycle 17: UVIS Bowtie Monitor

Ground testing revealed an intermittent hysteresis type effect in the UVIS detector (both CCDs) at the level of ~1%, lasting hours to days. Initially found via an unexpected bowtie-shaped feature in flatfield ratios, subsequent lab tests on similar e2v devices have since shown that it is also present as simply an overall offset across the entire CCD, i.e., a QE offset without any discernable pattern. These lab tests have further revealed that overexposing the detector to count levels several times full well fills the traps and effectively neutralizes the bowtie. Each visit in this proposal acquires a set of three 3×3 binned internal flatfields: the first unsaturated image will be used to detect any bowtie, the second, highly exposed image will neutralize the bowtie if it is present, and the final image will allow for verification that the bowtie is gone.

WFC3/UVIS 11912

UVIS Internal Flats

This proposal will be used to assess the stability of the flat field structure for the UVIS detector throughout the 15 months of Cycle 17. The data will be used to generate on- orbit updates for the delta-flat field reference files used in the WFC3 calibration pipeline, if significant changes in the flat structure are seen.

WFC3/UVIS/IR 11909

UVIS Hot Pixel Anneal

The on-orbit radiation environment of WFC3 will continually generate new hot pixels. This proposal performs the procedure required for repairing those hot pixels in the UVIS CCDs. During an anneal, the two-stage thermo-electric cooler (TEC) is turned off and the four-stage TEC is used as a heater to bring the UVIS CCDs up to ~20 deg. C. As a result of the CCD warmup, a majority of the hot pixels will be fixed; previous instruments such as WFPC2 and ACS have seen repair rates of about 80%. Internal UVIS exposures are taken before and after each anneal, to allow an assessment of the procedure’s effectiveness in WFC3, provide a check of bias, global dark current, and hot pixel levels, as well as support hysteresis (bowtie) monitoring and CDBS reference file generation. One IR dark is taken after each anneal, to provide a check of the IR detector.


Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)

HSTARS: (None)



FGS GSAcq 7 7
FGS REAcq 6 6
OBAD with Maneuver 6 6


SpaceRef staff editor.