Update lronaccal to use time dependent dark files and specific dark files for exp0

[victoronline]

Update to lronaccal to use time-dependent dark files for dark correction and use of specific dark files for images with exp code of zero.

Description

The dark average produced is dependant on which options are selected.

If the custom dark file option is selected, the provided dark file will be used.

If the image has an exposure code of zero, the nearest (time) dark files with exposure code of zero will be used.

If UseNearestTimeDarkFile option is selected, the dark file with the nearest time to the image will be used for dark correction.

If UseNearestTimeDarkFilePair option is selected, the pair of dark files that the image time lies between will be used, as long as the difference between dark files doesn't exceed 45 days. If a suitable pair is not found, the latest dark file taken before the image will be used.

The equation used:

pixel_dark_average =
avgDarkLine1_pixel * |darkfile1_time - time|   +   avgDarkLine2_pixel * |darkfile2_time - time|
/ (1.0 * ( |darkFile1_time - time| + |darkFile2_time - time| ) )

Related Issue

#4514

Motivation and Context

LROC images need dark correction that is time-dependent. Dark Files for this correction will be created regularly and placed in the data/mission/calibration/nac_darks/ directory for this purpose.

How Has This Been Tested?

The LROC science team has tested using these dark files for dark correction and has been using this time-intensive manual process for two years. This PR is an effort to incorporate into lronaccal.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Documentation change (update to the documentation; no code change)
• Breaking change (fix or feature that would cause existing functionality to change) of lronaccal = yes

Checklist:

• [ x] I have read and agree to abide by the Code of Conduct
• [ x] I have read the CONTRIBUTING document.
• [ x] My change requires a change to the documentation.
• [ x] I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.
• I have added myself to the .zenodo.json document.
• I have added any user impacting changes to the CHANGELOG.md document.

Licensing

This project is mostly composed of free and unencumbered software released into the public domain, and we are unlikely to accept contributions that are not also released into the public domain. Somewhere near the top of each file should have these words:

This work is free and unencumbered software released into the public domain. In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and all copyright interest in the software to the public domain.

• [x ] I dedicate any and all copyright interest in this software to the public domain. I make this dedication for the benefit of the public at large and to the detriment of my heirs and successors. I intend this dedication to be an overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.

[victoronline]

Did not pull down changes correctly. Will open a new PR.