Status Report

NASA Hubble Space Telescope Daily Report #4912

By SpaceRef Editor
August 25, 2009
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PERIOD COVERED: 5am August 18 – 5am August 19, 2009 (DOY 230/09:00z-231/09:00z)


ACS/WFC3 11465

ACS CCD Monitoring and Calibration for WFC3

This program is a smaller version of our routine CCD monitoring program, designed to run throughout SMOV, after which our regular Cycle 17 CAL proposal will begin. This program obtains the bias and dark frames needed to generate reference files for calibrating science data, and allows us to monitor detector noise and the growth of hot pixels.

NIC2/WFC3/IR 11548

NICMOS Imaging of Protostars in the Orion A Cloud: The Role of Environment in Star Formation

We propose NICMOS observations of a sample of 252 protostars identified in the Orion A cloud with the Spitzer Space Telescope. These observations will image the scattered light escaping the protostellar envelopes, providing information on the shapes of outflow cavities, the inclinations of the protostars, and the overall morphologies of the envelopes. In addition, we ask for Spitzer time to obtain 55-95 micron spectra of 75 of the protostars. Combining these new data with existing 3.6 to 70 micron photometry and forthcoming 5-40 micron spectra measured with the Spitzer Space Telescope, we will determine the physical properties of the protostars such as envelope density, luminosity, infall rate, and outflow cavity opening angle. By examining how these properties vary with stellar density (i.e. clusters vs groups vs isolation) and the properties of the surrounding molecular cloud; we can directly measure how the surrounding environment influences protostellar evolution, and consequently, the formation of stars and planetary systems. Ultimately, this data will guide the development of a theory of protostellar evolution.

STIS/CCD 11567

Boron Abundances in Rapidly Rotating Early-B Stars

Models of rotation in early-B stars predict that rotationally driven mixing should deplete surface boron abundances during the main-sequence lifetime of many stars. However, recent work has shown that many boron depleted stars are intrinsically slow rotators for which models predict no depletion should have occurred, while observations of nitrogen in some more rapidly rotating stars show less mixing than the models predict. Boron can provide unique information on the earliest stages of mixing in B stars, but previous surveys have been biased towards narrow-lined stars because of the difficulty in measuring boron abundances in rapidly rotating stars. The two targets observed as part of our Cycle 13 SNAP program 10175, just before STIS failed, demonstrate that it is possible to make useful boron abundance measurements for early-B stars with Vsin(i) above 100 km/s. We propose to extend that survey to a large enough sample of stars to allow statistically significant tests of models of rotational mixing in early-B stars.

STIS/CCD 11612

Eta Carinae’s Continuing Instability and Recovery – The 2009 Event

Eta Carinae is the only really observable example of structural recovery from a massive giant eruption, a “supernova imposter’ event. Moreover it is the only well-observed star above 100 Msun, and its 5.5-year-recurrent spectroscopic events provide extraordinary clues to its surface instability. This truly unique combination of attributes makes it valuable for understanding the most massive stars. A fresh development arose a few years ago: the star has brightened much faster than before, and appears to have entered a rapid stage in its post-eruption recovery.

A spectroscopic event will occur at 2009.0, soon after the planned HST servicing mission. Because of the recent secular trend, this event is expected to differ from its well- observed 2003.5 predecessor. The differences will be very important, because they offer clues to very-massive-star structural instabilities that can’t be observed in any other known way.

Some of the needed observations require HST’s high spatial resolution and UV coverage. We propose an efficient, well-chosen set of STIS and ACS observations around the critical time. If the servicing mission is too late for the event, then a subset of the observations will still be merited.

STIS/CCD 11844

CCD Dark Monitor Part 1

Monitor the darks for the STIS CCD.

STIS/CCD 11846

CCD Bias Monitor-Part 1

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/CCD 11852

STIS CCD Spectroscopic Flats C17

Obtain pixel-to-pixel lamp flat fields for the STIS CCD in spectroscopic mode.

STIS20 11402

STIS-20 NUV MAMA Dark Monitor

The STIS NUV-MAMA dark current is dominated by a phosphorescent glow from the detector window. Meta-stable states in this window are populated by cosmic ray impacts, which, days later, can be thermally excited to an unstable state from which they decay, emitting a UV photon. The equilibrium population of these meta-stable states is larger at lower temperatures; so warming up the detector from its cold safing will lead to a large, but temporary, increase in the dark current.

To monitor the decay of this glow, and to determine the equilibrium dark current for Cycle 17, four 1380s NUV-MAMA ACCUM mode darks should be taken each week during the SMOV period. Once the observed dark current has reached an approximate equilibrium with the mean detector temperature, the frequency of this monitor can be reduced to one pair of darks per week.

WFC3 11428

D2 Calibration Lamp Test

This proposal verifies the health and performance of the calsystem deuterium lamp and assesses the status of the major UV filters by taking a full set of internal flatfields. A total of three nominal and one short exposure are obtained for each filter in order to establish an initial baseline of flatfield data as well as to confirm lamp repeatability and provide a contamination check. Additional iterations of D2 internal flatfields will be taken as part of WFC-19, UVIS Internal Flats (proposal 11432).

This proposal corresponds to SMOV ID WFC3-15. It should not be run until after the successful completion of WFC-06, the UVIS detector functional test (proposal 11419) and WFC-11, the initial UVIS alignment (proposal 11424).

WFC3/ACS/IR 11590

Observing the IR Catastrophe in a Deflagration Type Ia Supernova

Our lack of understanding of Type Ia supernova (SN Ia) explosions limits our confidence in their use for cosmology. While there is broad agreement that these objects represent the explosions of white dwarfs, the details of the explosion mechanism are not well- understood. Recently, we have identified an internally homogeneous subclass of SNe Ia whose photometric and spectroscopic peculiarities make them quite distinct from normal SNe Ia. Models suggest we may be seeing the result of an explosion with a subsonic burning front, called a deflagration. We propose to test SN Ia models by obtaining late-time photometry for SN 2008A, a recent, nearby example of this subclass, using ACS and WFC3 on HST. We will accurately measure the late-time photometric decline rate and spectral energy distribution (SED). These observations will allow us to test whether the ejecta contain the large amount of oxygen predicted by certain models. We also aim to detect major evolution of the SED expected due to the “IR catastrophe”, a change in the dominant cooling mechanism in the ejecta, as generically predicted by models but only hinted at by current observations.

WFC3/ACS/UVI 11877

HST Cycle 17 and Post-SM4 Optical Monitor

This program is the cycle 17 implementation of the HST Optical Monitoring Program.

The 36 orbits comprising this proposal will utilize ACS (Wide Field channel) and WFC3 (UVIS channel) to observe stellar cluster members in parallel with multiple exposures over an orbit. Phase retrieval performed on the PSF in each image will be used to measure primarily focus, with the ability to explore apparent coma, and astigmatism changes in WFC3. The goals of this program are to: 1) monitor the overall OTA focal length for the purposes of maintaining focus within science tolerances 2) gain experience with the relative effectiveness of phase retrieval on WFC3/UVIS PSFs 3) determine focus offset between the imagers and identify any SI-specific focus behavior and dependencies

If need is determined, future visits will be modified to interleave WFC3/IR channel and STIS/CCD focii measurements.

WFC3/IR 11915

IR Internal Flat Fields

This program is the same as 11433 (SMOV) and depends on the completion of the IR initial alignment (program 11425). This version contains three instances of 37 internal orbits; to be scheduled early, middle, and near the end of Cycle 17, in order to use the entire 110-orbit allocation.

In this test, we will study the stability and structure of the IR channel flat field images through all filter elements in the WFC3-IR channel. Flats will be monitored, i.e. to capture any temporal trends in the flat fields, and delta flats produced. High signal observations will provide a map of the pixel-to-pixel flat field structure, as well as identify the positions of any dust particles.

WFC3/UVI 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 (11909), will be used to generate the necessary superbias and superdark reference files for the calibration pipeline (CDBS).

WFC3/UVI 11907

UVIS Cycle 17 Contamination Monitor

The UV throughput of WFC3 during Cycle 17 is monitored via weekly standard star observations in a subset of key filters covering 200-600nm and F606W, F814W as controls on the red end. The data will provide a measure of throughput levels as a function of time and wavelength, allowing for detection of the presence of possible contaminants.

WFC3/UVI 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.


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

HSTARS: (None)


18686-1 – Recover NICMOS to SAA Operate @ 230/16:18z

18690-0 – Execute ROP NS-12 to Reset STIS Error Counter @ 231/01:15z



FGS GSAcq 06 06
FGS REAcq 10 10
OBAD with Maneuver 06 06


Flash Report: NICMOS in SAA Operate

At 230/16:18 z, NICMOS successfully completed the transition from safe to SAA Operate via Ops Request 18686. At 17:59z, the three Focal Plane Assembly (FPA) temperature sensors were enabled via Ops Request 18689.

SpaceRef staff editor.