- Press Release
- Sep 27, 2022
NASA Hubble Space Telescope Daily Report #4924
HUBBLE SPACE TELESCOPE DAILY REPORT #4924
Continuing to Collect World Class Science
PERIOD COVERED: 5am September 3 – 5am September 4, 2009 (DOY 246/09:00z-247/09:00z)
External CTE Monitor
This program will obtain a direct calibration of photometric losses due to imperfect CTE by imaging stars in 47 Tuc.
FUV Detector Dark
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.
CCD Dark Monitor Part 1
Monitor the darks for the STIS CCD.
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.
CCD Sparse Field CTE Internal
CTE measurements are made using the “internal sparse field test”, along the parallel axis. The “Pos=” optional parameter, introduced during Cycle 11, is used to provide off- center MSM positionings of some slits. All exposures are internals.
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.
Galaxies at z~7-10 in the Reionization Epoch: Luminosity Functions to <0.2L* from Deep IR Imaging of the HUDF and HUDF05 Fields The first generations of galaxies were assembled around redshifts z~7-10+, just 500-800 Myr after recombination, in the heart of the reionization of the universe. We know very little about galaxies in this period. Despite great effort with HST and other telescopes, less than ~15 galaxies have been reliably detected so far at z>7, contrasting with the ~1000 galaxies detected to date at z~6, just 200-400 Myr later, near the end of the reionization epoch. WFC3 IR can dramatically change this situation, enabling derivation of the galaxy luminosity function and its shape at z~7-8 to well below L*, measurement of the UV luminosity density at z~7-8 and z~8-9, and estimates of the contribution of galaxies to reionization at these epochs, as well as characterization of their properties (sizes, structure, colors). A quantitative leap in our understanding of early galaxies, and the timescales of their buildup, requires a total sample of ~100 galaxies at z~7-8 to ~29 AB mag. We can achieve this with 192 WFC3 IR orbits on three disjoint fields (minimizing cosmic variance): the HUDF and the two nearby deep fields of the HUDF05. Our program uses three WFC3 IR filters, and leverages over 600 orbits of existing ACS data, to identify, with low contamination, a large sample of over 100 objects at z~7-8, a very useful sample of ~23 at z~8-9, and limits at z~10. By careful placement of the WFC3 IR and parallel ACS pointings, we also enhance the optical ACS imaging on the HUDF and a HUDF05 field. We stress (1) the need to go deep, which is paramount to define L*, the shape, and the slope alpha of the luminosity function (LF) at these high redshifts; and (2) the far superior performance of our strategy, compared with the use of strong lensing clusters, in detecting significant samples of faint z~7-8 galaxies to derive their luminosity function and UV ionizing flux. Our recent z~7.4 NICMOS results show that wide-area IR surveys, even of GOODS-like depth, simply do not reach faint enough at z~7-9 to meet the LF and UV flux objectives. In the spirit of the HDF and the HUDF, we will waive any proprietary period, and will also deliver the reduced data to STScI. The proposed data will provide a Legacy resource of great value for a wide range of archival science investigations of galaxies at redshifts z~2-9. The data are likely to remain the deepest IR/optical images until JWST is launched, and will provide sources for spectroscopic followup by JWST, ALMA and EVLA.
UVIS Internal Flats
This proposal will be used to assess the stability of the flat field structure for the UVIS detector. Flat fields will be obtained for all filters using the internal D2 and tungsten lamps.
This proposal corresponds to Activity Description ID WF19. It should execute only after the following proposals have executed: WF08 – 11421 WF09 – 11422 WF11 – 11424 WF15 – 11428
The Population of Compact Planetary Nebulae in the Galactic Disk
We propose to secure narrow- and broad-band images of compact planetary nebulae (PNe) in the Galactic Disk to study the missing link of the early phases of post-AGB evolution. Ejected AGB envelopes become PNe when the gas is ionized. PNe expand, and, when large enough, can be studied in detail from the ground. In the interim, only the HST capabilities can resolve their size, morphology, and central stars. Our proposed observations will be the basis for a systematic study of the onset of morphology. Dust properties of the proposed targets will be available through approved Spitzer/IRS spectra, and so will the abundances of the alpha-elements. We will be able thus to explore the interconnection of morphology, dust grains, stellar evolution, and populations. The target selection is suitable to explore the nebular and stellar properties across the Galactic Disk, and to set constraints on the galactic evolutionary models through the analysis of metallicity and population gradients.
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).
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.
A Dynamical-Compositional Survey of the Kuiper Belt: A New Window Into the Formation of the Outer Solar System
The eight planets overwhelmingly dominate the solar system by mass, but their small numbers, coupled with their stochastic pasts, make it impossible to construct a unique formation history from the dynamical or compositional characteristics of them alone. In contrast, the huge numbers of small bodies scattered throughout and even beyond the planets, while insignificant by mass, provide an almost unlimited number of probes of the statistical conditions, history, and interactions in the solar system. To date, attempts to understand the formation and evolution of the Kuiper Belt have largely been dynamical simulations where a hypothesized starting condition is evolved under the gravitational influence of the early giant planets and an attempt is made to reproduce the current observed populations. With little compositional information known for the real Kuiper Belt, the test particles in the simulation are free to have any formation location and history as long as they end at the correct point. Allowing compositional information to guide and constrain the formation, thermal, and collisional histories of these objects would add an entire new dimension to our understanding of the evolution of the outer solar system. While ground based compositional studies have hit their flux limits already with only a few objects sampled, we propose to exploit the new capabilities of WFC3 to perform the first ever large-scale dynamical-compositional study of Kuiper Belt Objects (KBOs) and their progeny to study the chemical, dynamical, and collisional history of the region of the giant planets. The sensitivity of the WFC3 observations will allow us to go up to two magnitudes deeper than our ground based studies, allowing us the capability of optimally selecting a target list for a large survey rather than simply taking the few objects that can be measured, as we have had to do to date. We have carefully constructed a sample of 120 objects which provides both overall breadth, for a general understanding of these objects, plus a large enough number of objects in the individual dynamical subclass to allow detailed comparison between and within these groups. These objects will likely define the core Kuiper Belt compositional sample for years to come. While we have many specific results anticipated to come from this survey, as with any project where the field is rich, our current knowledge level is low, and a new instrument suddenly appears which can exploit vastly larger segments of the population, the potential for discovery — both anticipated and not — is extraordinary.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
FGS GSAcq 6 6
FGS REAcq 9 9
OBAD with Maneuver 3 3
SIGNIFICANT EVENTS: (None)