Background Regeneration

Chip Stage

The background models are generated at the chip stage, and will be retained permanently, even after the other image data has been cleaned. These are small (13x13) images that contain the background samples that can be interpolated to construct the smooth background model that was subtracted from the science images.

Warp Stage

Previously, we have not generated warp stage background models. The new trunk (and next tag) will include the code to generate these models. They are similar to the chip stage models, which are interpolated onto a finer grid, and warped to match the science data. This increase in resolution is necessary to properly account for the inter-chip gaps. These models are still substantially smaller than the science images (~50x50).

Stack Stage

To construct the stack stage background model, all input warp background models are loaded, and the median value is selected for each model pixel. NAN and masked regions are excluded in this median, which should represent the "average" background model that was removed from all input images in the stack.

Applying a background model to an image

Generating a background restored image can be done using the ppBackground command:

 ppBackground restored_version -background input.mdl.fits -image input.fits -mask input.mask.fits

This can be done to either the warp or stack stage products.

Status

All the code is finished and committed to the trunk, but I am still checking the outputs.