WFC3 UVIS Observed PSF Search through MAST
To facilitate users in building WFC3 PSFs appropriate for their observations, we are making a full dataset of WFC3 observed PSFs available. The database contains more than 20 million PSFs, and include all WFC3/UVIS observations taken during 2009 to 2015. Users can use these PSFs to generate their own PSFs appropriate for their specific observations (filter/detector/focus-value etc.). Or they can use these PSFs to build delta-PSFs which they can use in conjunction with the library PSFs. These resulting PSFs are expected to be more representative of their observations, and hence may help in accurate photometry/astrometry.
The search parameters are briefly described below.
| Parameter | Description |
|---|---|
| ID | Unique ID for identifying the PSF within this particular image. The downloaded file will include this ID in the file name. |
| Focus | Model focus value taken from the webpages The model takes the breathing of the HST within the orbit into account. See the above links for more details about how the focus model. |
| Filter | Name of the filter used |
| PSF X Center | Central X value of the PSF. |
| PSF Y Center | Central Y value of the PSF |
| PSF Flux | Total flux (in electrons) within the PSF. |
| qfit | Quality of the PSF fit. Quality worsens as the qfit parameter increases: 0 is good, 1 is bad. |
| Exposure Time | in seconds |
| Aperture | UVIS1, UVIS2, etc (see handbook for details of the apertures) |
| Rootname | Root name of the image |
| Chip | CCD chip: Chip 1 or Chip 2 (Chip 1 corresponds to extension 4, or [sci,2], and Chip 2 corresponds to extension 1, or [sci,1] |
| Sky | Sky level per pixel in electrons around the pSF |
| Pixc | Value of the flux in the central pixel |
| Midexp | Time of the middle of the exposure in MJD |
| RA_TARG | RA of the observed target |
| DEC_TARG | DEc of the observed target |
| SUN Angle | Angle of the target with respect to the sun in degrees |
| FGS lock | Status of the FGS lock during the observations: Fine, or combination of fine and gyros, or gyros. |
| Shutter position | A or B (B has extra jitter in the first 0.3 sec) |
The PSFs can be visually inspected by clicking the “album” button. The download option allows users to download the raw, and the calibrated (flt and flc) files.
More details on the procedures for building PSFs and delta-PSFs will be provided later.