NASA Hubble Space Telescope Daily Report #5069
HUBBLE SPACE TELESCOPE DAILY REPORT #5069
Continuing to Collect World Class Science
PERIOD COVERED: 5am April 6 – 5am April 7, 2010 (DOY 096/09:00z-097/09:00z)
OBSERVATIONS SCHEDULED
ACS/WFC 11715
The Luminous Galactic Cepheid RS Puppis: A Geometric Distance from its Nested Light Echoes
RS Puppis is one of the most luminous Cepheids in the Milky Way (P = 41.4 days) and an analog of the bright Cepheids used to measure extragalactic distances. An accurate distance would help anchor the zero-point of the bright end of the period-luminosity relation, but at a distance of about 2 kpc it is too far away for a trigonometric parallax with existing instrumentation.
RS Pup is unique in being surrounded by a reflection nebula, whose brightness varies as pulses of light from the Cepheid propagate outwards. Members of our team have used ground-based imaging of the nebula to derive phase lags in the light variations of individual features in the nebula, and have inferred a seemingly very precise geometric distance to the star. However, there is an unavoidable ambiguity involving the cycle counts, which was resolved by assuming that the features lie in the plane of the sky. If this assumption is incorrect, a large systematic error would be introduced into the distance measurement.
We show that polarimetric imaging using the high spatial resolution of ACS/WFC and its ability to image close to the star can resolve this ambiguity and yield a reliable geometric distance to RS Pup. We will also obtain a wide-field multicolor image of the nebula, in order to study its morphology and the mass-loss history of the Cepheid.
COS/NUV/FUV 11673
Dynamics in the Atmosphere of the Evaporating Planet HD189733b
With HST/STIS, we detected and characterized the upper atmosphere of the extrasolar planet HD209458b, showing that the planet must be evaporating at a rate of ~10^10 g/s in a “blow-off” mechanism.
More recently, using ACS we concluded that HD189733b is also evaporating. However, because of the low resolution of the ACS prism spectroscopy, the escape rate and mechanism are still to be determined. This is one of the prime objectives of the present proposal.
COS observations of the absorption line profile with 15 km/s resolution will allow us to probe the dynamics of the escaping gas, and therefore to determine the escape rate. Simultaneous observations of the transit depth and spectral shape in several important lines (not only HI, but also OI, CII and possibly NI) will constrain the escape mechanism and allow us to distinguish between several scenarios. The results will enlighten the physical phenomenons at work in the exosphere of these extrasolar planets, and provide new constraints for the modeling of the evaporation of hot-Jupiters.
STIS/CC 11845
CCD Dark Monitor Part 2
Monitor the darks for the STIS CCD.
STIS/CC 11847
CCD Bias Monitor-Part 2
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.
WFC3/ACS/IR 11142
Revealing the Physical Nature of Infrared Luminous Galaxies at 0.3
WFC3/ACS/UVIS 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 11920
WFC3 IR Image Quality
The IR imaging performance over the detector will be assessed periodically (every 4 months) in two passbands to check for image stability. The field around star 58 in the open cluster NGC188 is the chosen target because it is sufficiently dense to provide good sampling over the FOV while providing enough isolated stars to permit accurate PSF (point spread function) measurement. It is available year-round and used previously for ACS image quality assessment. The field is astrometric, and astrometric guide stars will be used, so that the plate scale and image orientation may also be determined if necessary (as in SMOV proposals 11437 and 11443). Full frame images will be obtained at each of 4 POSTARG offset positions designed to improve sampling over the detector in F098M, F105W, and F160W. The PSFs will be sampled at 4 positions with subpixel shifts in filters F164N and F127M.
This proposal is a periodic repeat (once every 4 months) of the visits in SMOV proposal 11437 (activity ID WFC3-24). The data will be analyzed using the code and techniques described in ISR WFC3 2008-41 (Hartig). Profiles of encircled energy will be monitored and presented in an ISR. If an update to the SIAF is needed, (V2, V3) locations of stars will be obtained from the Flight Ops. Sensors and Calibrations group at GSFC, the (V2, V3) of the reference pixel and the orientation of the detector will be determined by the WFC3 group, and the Telescopes group will update and deliver the SIAF to the PRDB branch.
The specific PSF metrics to be examined are encircled energy for aperture diameter 0.25, 0.37, and 0.60 arcsec, FWHM, and sharpness. (See ISR WFC3 2008-41 tables 2 and 3 and preceding text.) ~20 stars distributed over the detector will be measured in each exposure for each filter. The mean, rms, and rms of the mean will be determined for each metric. The values determined from each of the 4 exposures per filter within a visit will be compared to each other to see to what extent they are affected by “breathing”. Values will be compared from visit to visit, starting with the values obtained during SMOV after the fine alignment has been performed, to see if the measures of the compactness of the PSF indicate degradation over time. The analysis will be repeated for stars on the inner part of the detector and stars on the outer part of the detector to check for differential degradation of the PSF.
As an example of the analysis, one can examine the sharpness of the F160W PSF exposures made during thermal vacuum testing (ISR WFC3 2008-41). To compare two samples, one can define the PSFs on each half of the detector (lower and upper) as a sample (with 7 and 8 PSFs, respectively). The mean, rms, and rms of the mean sharpness are 0.0826, 0.0067, and 0.0027 for one half, and 0.0773, 0.0049, and 0.0019 for the other. The difference of the means is 0.0053 and the statistical error in that difference is 0.0033, so the difference is not significant.
WFC3/IR 11926
IR Zero Points
We will measure and monitor the zeropoints through the IR filters using observations of the white dwarf standard stars, GD153, GD71 and GD191B2B and the solar analog standard star, P330E. Data will be taken monthly during Cycle 17. Observations of the star cluster, NGC 104, are made twice to check color transformations. We expect an accuracy of 2% in the wide filter zeropoints relative to the HST photometric system, and 5% in the medium- and narrow-band filters.
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/UV 11635
Improve the Measurement of Vesta’s Pole Orientation to Support Dawn Mission
NASA?s Dawn spacecraft is scheduled to go into orbit around the main belt asteroid 4 Vesta in July 2011. Currently the project is using a 3- pole position uncertainty of Vesta of 12 for spacecraft trajectory design. We have determined that with an additional set of Hubble observations at Vesta?s next opposition in February 2010, that the pole position uncertainty can be reduced by a factor of 4. This will reduce both cost and risk to the Dawn mission, and is likely to increase the stay time at Vesta and will add to the scientific return of the mission. The requested observing window in February 2010 is the last and single best opportunity that can benefit the Dawn mission, but it is before the start of the next HST Cycle.
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.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)
HSTARS: (None)
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
SCHEDULED SUCCESSFUL
FGS GSAcq 7 7
FGS REAcq 10 10
OBAD with Maneuver 7 7
SIGNIFICANT EVENTS: (None)
