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uchcoord stsdas.hst_calib.wfpc



uchcoord -- Update WFPC2 group parameters affected by plate scale, shift, and rotation changes due to PDB updates.


uchcoord input update


The task updates position related group parameters of WFPC2 images, i.e. CD matrices, CRPIX's, CRVAL's, and ORIENTAT. The plate scales, reference pixel locations, and chip rotation angles stored in the Project Data Base (PDB) and used by the pipeline to populate WFPC2 files have undergone changes since the instrument was first commissioned. This task updates affected group parameters of earlier observations to more accurate values and therefore cohere with images obtained at different epochs. A history of the updating will be added to the image header.

A new keyword PDBEPOCH will be added or updated in the header. This keyword is the epoch (in Modified Julian date) corresponding to the PDB parameters applied or updated to the input image. Because of this new keyword, if there are more PDB updates in the future, this task will be able to properly handle images already been processed by this task in the past.

This task supersedes the task uchscale and is backward compatible. If you have used uchscale to update the plate scales on WFPC2 files, this task will recognize the previous update and will not over-correct the plate scale.


input [string]
Input images. They must be WFPC2 images.
update [boolean]
Update the group parameters? If set to no, this task will just print out the epoch of PDB applied to this image and plate scales.


1. Update the group parameters of abc.c0h.

wf> uchcoord abc.c0h yes

2. Examine the plate scales of all .c0h files.

wf> uchcoord *.c0h no


(1) WFPC2 Instrument Handbook (version 3.0, Jun 1995), Sec. 2.9. (2)



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