Possible Overlaps Between Blobs, Grism Apertures, and Dithers
Abstract
We present a investigation into possible overlaps between the known IR blobs with the grism aperture reference positions and the IR dither patterns. Each aperture was designed to place the science target (e.g. a specific star) on a cosmetically clean area of the IR detector. Similarly, the dither patterns were designed to mitigate cosmetic defects by rarely (or ideally never) placing such targets on known defects. Because blobs accumulate with time, the originally defined apertures and dither patterns may no longer accomplish their goals, it is important to reverify these combinations. We find two potential overlaps between the blob, aperture, and dither combinations, but do not recommend any changes to the current suite of aperture references positions and/or dither patterns for two reasons. First, one of the overlaps occurs with a dither/aperture combination that is seldom used for high-value science operations, but rather more common for wide-field surveys/mosaics. Second, the other overlap is 8.7 pix from a blob that has a fiducial radius of 10 pix, which already represents a very conservative distance. We conclude that a similar analysis should be repeated as new blobs occur, to continue to ensure ideal operations for high-value science targets. The purpose of this report is to document the analysis in order to facilitate its repetition in the future.
- Publication:
-
Space Telescope WFC Instrument Science Report
- Pub Date:
- June 2017
- Bibcode:
- 2017wfc..rept...16R
- Keywords:
-
- Hubble Space Telescope;
- HST;
- Space Telescope Science Institute;
- STScI;
- WFC3;
- infrared blobs;
- IR blobs