uses separate paths for processing UVIS and IR images, as listed in Table 3.1
automatically calls the appropriate tasks, but each may be run separately if the user desires some variation from the normal processing. wf3ccd
are used for processing UVIS images, while IR image processing is done with wf3ir
. The wf3rej
program is used for both UVIS and IR images to combine multiple exposures contained in a CR-SPLIT
set. Figure 3.2
shows the calwf3
flow of data in the calwf3
first subtracts the bias and trims the overscan regions from the image. If an associated set of UVIS CR-SPLIT
images is being processed, all of the overscan-trimmed images are sent through wf3rej
to be combined and receive cosmic-ray rejection. The resulting combined image then receives final calibration with wf32d
, which includes dark subtraction and flat fielding. If there are multiple sets of CR-SPLIT
images in an association, each set goes through the cycle of wf3ccd
All individual IR images are processed with wf3ir
. If an association of IR REPEAT-OBS
images is being processed, the calibrated images are combined into a single product using wf3rej
. If there are multiple sets of REPEAT-OBS
images in an association, each set goes through the cycle of wf3ir
During automatic pipeline processing, AstroDrizzle
. All calibrated images are corrected for geometric distortion correction and associated sets of dithered images are combined into a single product. See Chapter 4
for more information on geometric distortion.
The individual UVIS processing steps performed by wf3ccd
are shown in Figure 3.2
and Figure 3.3
, respectively. The reference files needed for each step and the calibration switches controlling them are also listed. The calibration steps are as follows:
Individual IR processing steps performed by wf3ir
are shown in Figure 3.4
, along with the names of reference files and calibration switches. The steps are as follows:
Detailed descriptions of each calibration step are given in Section 3.4
. In general, the first nine steps - through conversion to count rates - are applied independently to each readout of the IR MultiAccum exposure stack. The up-the-ramp fitting processes then produces a single image representing the best-fit count rate for each pixel. The final two calibration steps are then applied to that single image, as well as to each read of the MultiAccum stack.
processing software and its associated routines, such as wf3ccd
, are now available independent of the IRAF environment as part of the HSTCAL package.
All versions of calwf3
past 3.0 represent the new HSTCAL software.
While both CR-SPLIT
exposures from an association get combined using calwf3
, dithered observations from an association do not. AstroDrizzle
must be used to create a dither-combined product.