- Press Release
- September 24, 2022
NASA Hubble Space Telescope Daily Report #4929
HUBBLE SPACE TELESCOPE DAILY REPORT #4929
Continuing to Collect World Class Science
PERIOD COVERED: 5am September 11 – 5am September 14, 2009 (DOY 254/09:00z-257/09:00z)
Determining the Rotational Phase of Comet 9P/Tempel 1 in Support of the StardustNExT Mission
A primary objective of the StardustNExT mission is to image the crater created by NASA’s Deep Impact (DI) mission. The 12-year ground- and space-based DI observing campaign provided an exceptional data set for investigating the rotation of comet 9P/Tempel 1. The just-completed analysis shows that the spin period increased in a stepwise manner through the perihelia in 2000 and 2005, due to an outgassing of water from a southern jet. Our water-sublimation jet torque model has been moderately successful in predicting the integrated change in the nucleus longitude at the 2005 perihelion and beyond, and has been used to predict the rotation state at the planned Stardust-NExT encounter just after perihelion on 02/14/2011. We propose a 19-orbit Hubble program to perform light curve observations of 9P/Tempel 1 that will allow us to determine the time-of-arrival adjustment of the Stardust-NExT spacecraft trajectory that is needed to ensure that the spacecraft arrives at encounter with the (as yet unseen) artificial DI crater at the sub-spacecraft point and fully illuminated by the sun. The trajectory correction maneuver is in Feb 2010, and we need to know the nucleus rotation phase to a precision of 1% and the period to 10 sec by Jan 2010. HST is the only facility capable of obtaining the high-quality data necessary to determine the shape and phase of the rotational light curve. When combined with ground-based data 2-3 months later, we will achieve the required precision.
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.
UVIS G280 Wavelength Calibration
Wavelength calibration of the UVIS G280 grism will be established using observations of the Wolf Rayet star WR14. Accompanying direct exposures will provide wavelength zeropoints for dispersed exposures. The calibrations will be obtained at the central position of each CCD chip and at the center of the UVIS field. No additional field- dependent variations will be obtained.
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 External and Internal CTE Monitor
CCD detector Charge Transfer Inefficiency (CTI)-induced losses in photometry and astrometry will be measured using observations of the rich open cluster NGC6791 and with the EPER (Extended Pixel Edge Response) method using tungsten lamp flat field exposures. Although we do not expect to see CTE effects at the outset of Cycle 17, this CTE monitoring program is the first of a multi-cycle program to monitor and establish CTE-induced losses with time. We expect to measure CTE effects with a precision comparable to the ACS measurements.
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.
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.
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 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).
CCD Daily Monitor (Part 1)
This program comprises basic tests for measuring the read noise and dark current of the ACS WFC and for tracking the growth of hot pixels. The recorded frames are used to create bias and dark reference images for science data reduction and calibration. This program will be executed four days per week (Mon, Wed, Fri, Sun) for the duration of Cycle 17. To facilitate scheduling, this program is split into three proposals. This proposal covers 352 orbits (22 weeks) from 31 August 2009 to 31 January 2010.
MAMA Spectroscopic Sensitivity and Focus Monitor
the purpose of this proposal is to monitor the sensitivity of each MAMA grating mode to detect any change due to contamination or other causes, and to also monitor the STIS focus in a spectroscopic and an imaging mode.
STIS CCD Spectroscopic Flats C17
The purpose of this proposal is to obtain pixel-to-pixel lamp flat fields for the STIS CCD in spectroscopic mode.
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.
CCD Dark Monitor Part 1
The purpose of this proposal is to monitor the darks for the STIS CCD.
HST/FGS Astrometric Search for Young Planets Around Beta Pic and AU Mic
AU Mic is a nearby Vega-type debris disk star. Its disk system has been spatially resolved in exquisite detail, predominantly via the ACS coronagraph and WFPC2 cameras onboard HST. These images exhibit a wealth of morphological features which provide compelling indirect evidence that AU Mic likely harbors short-period planetary body/bodies. We propose to use the superlative astrometric capabilities of HST/FGS to directly detect these planets, hence provide the first direct planet detection in a Vega- type system whose disk has been imaged at high spatial resolution.
An Astrometric Calibration of Population II Distance Indicators
In 2002, HST produced a highly precise parallax for RR Lyrae. That measurement resulted in an absolute magnitude, M(V)= 0.61+/-0.11, a useful result, judged by the over ten refereed citations each year since. It is, however, unsatisfactory to have the direct, parallax-based, distance scale of Population II variables based on a single star. We propose, therefore, to obtain the parallaxes of four additional RR Lyrae stars and two Population II Cepheids, or W Vir stars. The Population II Cepheids lie with the RR Lyrae stars on a common K-band Period-Luminosity relation. Using these parallaxes to inform that relationship, we anticipate a zero-point error of 0.04 magnitude. This result should greatly strengthen confidence in the Population II distance scale and increase our understanding of RR Lyrae star and Pop. II Cepheid astrophysics.
The Ages of Globular Clusters and the Population II Distance Scale
Globular clusters are the oldest objects in the universe whose age can be accurately determined. The dominant error in globular cluster age determinations is the uncertain Population II distance scale. We propose to use FGS 1R to obtain parallaxes with an accuracy of 0.2 milliarcsecond for 9 main sequence stars with [Fe/H] < -1.5. This will determine the absolute magnitude of these stars with accuracies of 0.04 to 0.06mag. This data will be used to determine the distance to 24 metal-poor globular clusters using main sequence fitting. These distances (with errors of 0.05 mag) will be used to determine the ages of globular clusters using the luminosity of the subgiant branch as an age indicator. This will yield absolute ages with an accuracy of 5%, about a factor of two improvement over current estimates. Coupled with existing parallaxes for more metal-rich stars, we will be able to accurately determine the age for globular clusters over a wide range of metallicities in order to study the early formation history of the Milky Way and provide an independent estimate of the age of the universe.
The Hipparcos database contains only 1 star with [Fe/H] < -1.4 and an absolute magnitude error less than 0.18 mag which is suitable for use in main sequence fitting. Previous attempts at main sequence fitting to metal-poor globular clusters have had to rely on theoretical calibrations of the color of the main sequence. Our HST parallax program will remove this source of possible systematic error and yield distances to metal- poor globular clusters which are significantly more accurate than possible with the current parallax data. The HST parallax data will have errors which are 10 times smaller than the current parallax data. Using the HST parallaxes, we will obtain main sequence fitting distances to 11 globular clusters which contain over 500 RR Lyrae stars. This will allow us to calibrate the absolute magnitude of RR Lyrae stars, a commonly used Population II distance indicator.
The Host Environments of Type Ia Supernovae in the SDSS Survey
The Sloan Digital Sky Survey Supernova Survey has discovered nearly 500 type Ia supernovae and created a large, unique, and uniform sample of these cosmological tools. As part of a comprehensive study of the supernova hosts, we propose to obtain Hubble ACS images of a large fraction of these galaxies. Integrated colors and spectra will be measured from the ground, but we require high-resolution HST imaging to provide accurate morphologies and color information at the site of the explosion. This information is essential in determining the systematic effects of population age on type Ia supernova luminosities and improving their reliability in measuring dark energy. Recent studies suggest two populations of type Ia supernovae: a class that explodes promptly after star-formation and one that is delayed by billions of years. Measuring the star-formation rate at the site of the supernova from colors in the HST images may be the best way to differentiate between these classes.
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.
Elucidating the Mystery of the Io Footprint Time Variations
The Io UV footprint (IFP) is an auroral emission on Jupiter consisting of one or more spots resulting from the electromagnetic interaction between Io and the Jovian magnetosphere. Recent UV HST observations of the Jovian aurora raised new issues and put previous interpretations under question. Dedicated STIS Time-Tag observations based on only 3 HST orbits will help us to directly answer the following questions and test new hypothesis on the physics driving their associated phenomenon.
The proposed observations will determine whether the previously observed short timescale (~2 min) variations of the IFP are periodic or burst events. If the (quasi-) periodicity is established, these constraints will help us to understand the origin of these variations. These observations will also clarify the conditions of occurrence of the unexpected quasi-simultaneous variations of the southern multiple spots of the IFP. Moreover, we propose to observe the emergence of the southern leading (or precursor) spot and the possible evolution of its brightness. These two elements might validate or exclude the recently proposed idea that cross-hemisphere electron beams or strong non- linearities of the electromagnetic interaction explain the presence of the leading and secondary spots.
Distances of Planetary Nebulae from SNAPshots of Resolved Companions
REliable distances to individual planetary nebulae (PNe) in the Milky Way are needed to advance our understanding of their spatial distribution, birthrates, influence on galactic chemistry, and the luminosities and evolutionary states of their central stars (CSPN). Few PNe have good distances, however. One of the best ways to remedy this problem is to find resolved physical companions to the CSPN and measure their distances by photometric main-sequence fitting. We have previously used HST to identify and measure probable companions to 10 CSPN, based on angular separations and statistical arguments only. We now propose to use HST to re-observe 48 PNe from that program for which additional companions are possibly present. We then can use the added criterion of common proper motion to confirm our original candidate companions and identify new ones in cases that could not confidently be studied before. We will image the region around each CSPN in the V and I bands, and in some cases in the B band. Field stars that appear close to the CSPN by chance will be revealed by their relative proper motion during the 13+ years since our original survey, leaving only genuine physical companions in our improved and enlarged sample. This study will increase the number of Galactic PNe with reliable distances by 50 percent and improve the distances to PNe with previously known companions.
Galaxy-Scale Strong Lenses from the CFHTLS Survey
We aim to investigate the origin and evolution of early-type galaxies using gravitational lensing, modeling the mass profiles of objects over a wide range of redshifts. The low redshift (z = 0.2) sample is already in place following the successful HST SLACS survey; we now propose to build up and analyze a sample of comparable size (~50 systems) at high redshift (0.4 < z < 0.9) using HST WFC3 Snapshot observations of lens systems identified by the SL2S collaboration in the CFHT legacy survey.
A Search for Astrometric Companions to Very Low-Mass, Population II Stars
We propose to carry out a Snapshot search for astrometric companions in a subsample of very low-mass, halo subdwarfs identified within 120 parsecs of the Sun. These ultra-cool M subdwarfs are local representatives of the lowest-mass H burning objects from the Galactic Population II. The expected 3-4 astrometric doubles that will be discovered will be invaluable in that they will be the first systems from which gravitational masses of metal-poor stars at the bottom of the main sequence can be directly measured.
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.
COS NUV Imaging Performance Verification
This activity is designed to verify the performance of the COS/NUV imaging mode. In particular, the PSF quality will be assessed and the plate scale will be measured. The throughput of the Mirror A with both the PSA and BOA will be fully calibrated by observing an appropriate HST flux standard star, and will be characterized as a function of location within the aperture by moving the star from the center to various positions with a grid pattern. The relative throughput of Mirror A vs. Mirror B will also be evaluated in the center of both the PSA and BOA. This activity will be structured in a way that will also allow for testing of the drift following the OSM motion in imaging mode and for testing of the image stability within an orbit and over several orbits.
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 – Proposal 11421
WF09 – Proposal 11422
WF11 – Proposal 11424
WF15 – Proposal 11428
The Co-Evolution of Spheroids and Black Holes in the Last Six Billion Years
The masses of giant black holes are correlated with the luminosities, masses, and velocity dispersions of the bulges of their host galaxies. This empirical correlation of phenomena on widely different scales (from pcs to kpcs) suggests that the formation and evolution of galaxies and central black holes are closely linked. In Cycle 13, we have started a campaign to map directly the co-evolution of spheroids and black-holes by measuring in observationally favorable redshift windows the empirical correlations connecting their properties. By focusing on Seyfert 1s, where the nucleus and the stars contribute comparable fractions of total light, black hole mass and bulge dispersion are obtained from Keck spectroscopy. HST is required for accurate measurement of the non- stellar AGN continuum, the morphology of the galaxy, and the structural parameters of the bulge. The results at z=0.36 indicate a surprisingly fast evolution of bulges in the past 4 Gyrs (significant at the 95%CL), in the sense that bulges were significantly smaller for a given black hole mass. Also, the large fraction of mergers and disturbed galaxies (4+2 out of 20) identifies gas-rich mergers as the mechanisms responsible for bulge- growth. Going to higher redshift – where evolutionary trends should be stronger – is needed to confirm these tantalizing results. We propose therefore to push our investigation to the next suitable redshift window z=0.57 (lookback-time 6 Gyrs). Fifteen objects are the minimum number required to map the evolution of the empirical correlations between bulge properties and black-hole mass, and to achieve a conclusive detection of evolution (>99%CL).
The Structure of Early-type Galaxies: 0.1-100 Effective Radii
The structure, formation and evolution of early-type galaxies is still largely an open problem in cosmology: how does the Universe evolve from large linear scales dominated by dark matter to the highly non-linear scales of galaxies, where baryons and dark matter both play important, interacting, roles? To understand the complex physical processes involved in their formation scenario, and why they have the tight scaling relations that we observe today (e.g. the Fundamental Plane), it is critically important not only to understand their stellar structure, but also their dark-matter distribution from the smallest to the largest scales. Over the last three years the SLACS collaboration has developed a toolbox to tackle these issues in a unique and encompassing way by combining new non-parametric strong lensing techniques, stellar dynamics, and most recently weak gravitational lensing, with high-quality Hubble Space Telescope imaging and VLT/Keck spectroscopic data of early-type lens systems. This allows us to break degeneracies that are inherent to each of these techniques separately and probe the mass structure of early-type galaxies from 0.1 to 100 effective radii. The large dynamic range to which lensing is sensitive allows us both to probe the clumpy substructure of these galaxies, as well as their low-density outer haloes. These methods have convincingly been demonstrated, by our team, using smaller pilot-samples of SLACS lens systems with HST data. In this proposal, we request observing time with WFC3 and NICMOS to observe 53 strong lens systems from SLACS, to obtain complete multi-color imaging for each system. This would bring the total number of SLACS lens systems to 87 with completed HST imaging and effectively doubles the known number of galaxy- scale strong lenses. The deep HST images enable us to fully exploit our new techniques, beat down low-number statistics, and probe the structure and evolution of early-type galaxies, not only with a uniform data-set an order of magnitude larger than what is available now, but also with a fully-coherent and self-consistent methodological approach!
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)
12013 – REAcq(2,3,3) scheduled at 255/06:42:04z – 06:46:30z was observed to have failed to RGA Hold (gyro control) due to search radius limit exceeded on FGS-2.
Observations affected: STIS 74 – 76, Proposal ID# 11860
COMPLETED OPS REQUEST:
18700-0 – Null genslew for proposal 11492 – slot 1 @ 254/19:30z
COMPLETED OPS NOTES: (None)
FGS GSAcq 37 37
FGS REAcq 11 10
OBAD with Maneuver 24 24
SIGNIFICANT EVENTS: (None)