Is exptime weighting not applied when input weight image is None?

[mcara]

trafficstars

Please refer to:

https://github.com/spacetelescope/drizzlepac/blob/ed40f611bf9bc040485493a79ed0beae70e3c131/src/cdrizzlebox.c#L554-L560

It looks like when input weight image is not provided, exptime or expsq scaling is not performed and all images are weighted equally. This unexpected (to me).

[stscijgbot-hstdp]

This issue is tracked on JIRA as HLA-1184.

[stsci-hack]

This seems to make perfect sense to me. Weights are hard-coded in drizzlepac to be provided under all circumstances (see lines 898-905 in drizzlepac\adrizzle.py) and provide the exptime or IVM weights on input to this C code. Also, if no weights are provided on input, the code has no other information to use to weight the images, so weighting them equally makes as much sense as anything. At least, that behavior is predictable and explainable.