WFC3 UVIS Shutter Vibration-Induced Image Blur
نویسنده
چکیده
During image quality testing in the third and final thermal-vacuum test of the integrated WFC3 instrument, an anomaly was discovered whereby the width and peak signal fraction of short exposure PSF images were observed to modulate for alternate exposures in a series. This behavior was traced to vibration of the UVIS shutter when its servo-control loop is enabled, which is believed to induce small (mas level) pointing jitter in the optics, most likely the pick-off mirror and the corrector mechanism (M1) mirror. We present model computations of the effects of this vibration on several PSF parameters for a range of exposure times, wavelengths and (currently uncertain) degree of severity of the vibration expected on orbit. Only very short (<10s) exposures are likely to be significantly affected; this may be partially mitigated by obtaining such exposures using the better-performing side of the shutter.
منابع مشابه
Preliminary WFC3 UVIS PSF Evaluation
We have made an initial assessment of the image quality of the WFC3 UVIS channel with its flight detector installed. Point source measurements at four field positions and four wavelengths indicate excellent imaging performance for the UVIS channel, with CEI encircled energy specifications readily achieved.
متن کاملWFC3 SMOV Proposal 11549: Image Stability
I review the image stability tests performed during the Servicing Mission Observatory Verification (SMOV) campaign for the Wide Field Camera 3 (WFC3). These tests were performed using repeated observations of globular clusters with the telescope oriented at hot and cold thermal attitudes. As expected from ground tests in 2007, the WFC3 image stability is slightly worse than specifications. The ...
متن کاملWFC3 TV2 Testing: Image Stability
ABSTRACT I review the image stability tests performed during the second thermal-vacuum (TV) campaign of WFC3. In the first TV campaign, significant drifts were seen in both channels in response to induced thermal changes in the instrument, but subsequent analysis indicated that the induced temperature variations were unrealistically large (compared to on-orbit conditions). In the current tests,...
متن کاملWFC3 UVIS High-resolution Imaging Performance
The sharp and stable point spread function of HST and WFC3 allows for the detection of stellar companions at small offsets from target stars. Deep images obtained through six UVIS filters are used to assess this ability to detect faint companions of brighter targets. Analogous capabilities from the ground make use of Adaptive Optics and Speckle imaging. We contrast the capabilities of HST/WFC3 ...
متن کاملPhotometric Repeatability of Scanned Imagery: UVIS
We provide the preliminary results of a study on the photometric repeatability of spatial scans of bright, isolated white dwarf stars with the UVIS channel of the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST). We analyze straight-line scans from the first pair of identical orbits of HST program 14878 to assess if sub 0.1% repeatability can be attained with WFC3/UVIS. This study...
متن کامل