219th American Astronomical Society Meeting

WFC3: Charge Transfer Efficiency and Charge Injection in the UVIS Detectors
Devices in low-earth orbit are particularly susceptible to the cumulative effects of radiation damage and the Hubble Space Telescope Wide Field Camera 3 (HST/WFC3) UVIS detectors, installed in May 2009, are no exception. Such damage not only generates new hot pixels but also degrades the charge transfer efficiency (CTE), causing a loss in source signal due to charge traps as well as a systematic shift in the object centroid as the trapped charge is slowly released during readout. Based on an analysis of both internal and external monitoring data, we provide an overview of the consequences of the more than 2.5 years of radiation damage to the WFC3 CCD cameras. The advantages and disadvantages of available mitigation options are discussed, including use of the WFC3 charge injection capability, a mode now available to observers, and the status of an empirical correction similar to the one adopted for the HST Advanced Camera for Surveys (ACS).
S. Baggett, K. Noeske, J. Anderson, J. Biretta, T. Borders, H. Bushouse, V. Khozhurina-Platais, J. MacKenty, L. Petro, and the WFC3 team 19 Jan 2012 (pdf)

WFC3 UVIS: Improved Flat Fields
We describe the new improved flat fields for WFC3 UVIS. These corrects for a reflection ghost (the flare) that is present in the previous ground-based flat fields. In addition, photometry of star in the star cluster Omega Centauri taken at different orientations and dither positions are used to correct for the difference in optical path between the ground illumination simulation and the actual HST. The new flat fields typically corrects photometry by 0.006-0.018 mag, depending on filter. The maximum change in photometry is 0.03-0.06 mag. New flat field for all 42 UVIS full frame filters have been used by the STScI pipeline since December 14, 2011.
Tomas Dahlen, Jennifer Mack, Elena Sabbi, and the WFC3 Team 24 Jan 2012 (pdf)

WFC3: Spatially-scanned Spectra of Exoplanet Transits (and more)
Spatial scanning is expected to have some advantages over staring-mode observations with the HST WFC3 instrument, especially for very bright stars, i.e. those that intrinsically can provide the highest sensitivity observations. We analyze 1.1-1.7 micron spectra of a transit of the super-Earth GJ1214b obtained 2011-4-18 during re- commissioning of a technique for spatially scanning the Hubble Space Telescope. These are the first data of this type obtained with the HST instrument WFC3. Results are directly compared to staring-mode observations with the same instrument of the same target by Berta et al. (2011). We also describe a case study of the sub-Neptune-sized planet HD 97658b in terms of proposed observations and what they may reveal of that planet. We also summarize publicly-available descriptions of additional HST programs that use the spatial-scanning technique.
P. R. McCullough, Z. K. Berta, A. W. Howard, J. MacKenty, and the WFC3 Team 19 Jan 2012 (pdf)

AstroDrizzle: Optimally Combining Subsampled WFC3 & ACS Data
AstroDrizzle is an improved STScI software tool for combining dithered HST images and removing geometric distortion. We present the results using AstroDrizzle to combine data taken from multiple detectors over several epochs, including WFC3 in both the UVIS and IR channels and early epoch ACS/WFC images. Using the spiral galaxy "NGC 3370" as an example, we will show improvements to the standard pipeline products that are achievable by optimizing the image combination when observations are obtained with sub-pixel dithering. We also compare the improvement in the usability over the earlier generation software MultiDrizzle. As a part of our final product we will make the test data available online, along with a cookbook detailing the process in a methodical manner, allowing users to reproduce the multi-channel optimally combined products using the new software.!
A. Rajan, J. Mack, H. Bushouse, M. Dulude, L. Petro, N. Pirzkal, and the WFC3 Team 19 Jan 2012 (pdf)

WFC3: Cycle 19 Calibration Program
The WFC3 Cycle 19 calibration program has been designed to measure and monitor the behavior of both the UVIS and IR channels. The program was designed with the actual usage of WFC3 in mind, to provide the best calibration data for the approved scientific programs. During the cycle the WFC3 team is using a total of 125 external (pointed observations) and 1587 internal orbits (data are acquired during occultation), divided in 29 different programs, which can be divided in 6 categories: Monitor, Photometry, Spectroscopy, Detectors, Flatfields and Image Quality.
E. Sabbi, J. MacKenty, S. Deustua, and the WFC3 Team 19 Jan 2012 (pdf)