Exposure Level Processing

Class:

romancal.pipeline.ExposurePipeline

Alias:

exposure_pipeline

The ExposurePipeline applies detector-level corrections to given exposure types (imaging, prism, and grism.). It is applied to one exposure at a time. It is sometimes referred to as “ramps-to-slopes” processing, because the input raw data are in the form of ramps containing accumulating counts from the non-destructive detector readouts and the output is a corrected countrate (slope) image.

The list of steps applied by the ExposurePipeline pipeline is shown in the table below.

Step	WFI-Image	WFI-Prism	WFI-Grism
dq_init	✓	✓	✓
saturation	✓	✓	✓
refpix	✓	✓	✓
linearity	✓	✓	✓
dark_current	✓	✓	✓
ramp_fitting	✓	✓	✓
assign_wcs	✓	✓	✓
flatfield	✓
photom	✓
source_catalog	✓
tweakreg	✓

Arguments

The exposure pipeline has no arguments

Inputs

3D raw data

Data model:

RampModel

File suffix:

_uncal

The input to the ExposurePipeline can be a single raw exposure, e.g. “r0008308002010007027_0019_wfi01_uncal.asdf”, which contains the original raw data from all of the detector readouts in the exposure ( ngroups x ncols x nrows ). The raw data may also be input using an association file.

If the ExposurePipeline is given a single file the final alignment to Gaia will be done with the sources found in the exposure. If multiple exposures exist in the association file then the final alignment will use all the sources found in the exposures (see tweakreg).

Note that in the operational environment, the input will be in the form of a RawScienceModel, which only contains the 3D array of detector pixel values, along with some optional extensions. When such a file is loaded into the pipeline, it is immediately converted into a RampModel, and has all additional data arrays for errors and Data Quality flags created and initialized.

When the ExposurePipeline processes a fully saturated input (all pixels flagged as saturated). The corresponding output image will:

• contain all 0 data arrays

• contain all 0 variance arrays

• not be processed by steps beyond saturation

A single fully saturated input will also cause tweakreg to be skipped for all input images.

Outputs

2D Image model

Data model:

ImageModel

File suffix:

_cal

Catalog file (SourceCatalog)

The catalog data is in

Data model:

astropy.table.Table

File suffix:

_cat

Segmentation Map (SegmentationMapModel)

The segmentation map is

Data model:

MosaicSegmentationMapModel

File suffix:

_segm

Result of applying all pipeline steps up through the tweakreg step is to produce calibrated data with the image WCS aligned to Gaia, and is 2D image data, which will have one less data dimensions as the input raw 3D data. In addition to being a 2-dimensional image the output from the pipeline has the reference pixels removed from the edges of the science array and saved as additional 3D arrays. The source catalog and segmentation map from the individual exposues is also saved.

WFI Level 1/Level 2 WCS (WfiWcsModel)

Data model:

WfiWcsModel

File suffix:

_wcs

Contains a copy of the final, GAIA-aligned, Level 2 Generalized World Coordinate System (GWCS) information along with a modified Level 1 GWCS which accounts for the border pixels. The Level 1 GWCS can be used directly with the related Level 1 product.