Introduction

Purpose and Scope

This document specifies the format of each calibration reference file used by the JWST Calibration pipeline for DMS Build 7, satisfying requirement DMS-653 (“The format of each calibration reference file shall be specified in the JWST Calibration Reference File Specification Document.”) The corresponding code internal delivery was packaged as Release Candidate 7 of Build 7. Many calibration steps in the DMS Build 7 Calibration Pipeline require reference files retrieved from CRDS. This document is intended to be a reference guide to the formats of reference files for steps requiring them, and is not intended to be a detailed description of each of those pipeline steps.

Data Quality Flags

Within science data files, the PIXELDQ flags are stored as 32-bit integers; the GROUPDQ flags are 8-bit integers. The meaning of each bit is specified in a separate binary table extension called DQ_DEF. The binary table has the format presented in Table 1, which represents the master list of DQ flags. Only the first eight entries in the table below are relevant to the GROUPDQ array. All calibrated data from a particular instrument and observing mode have the same set of DQ flags in the same (bit) order. For Build 7, this master list will be used to impose this uniformity. We may eventually use different master lists for different instruments or observing modes.

Within reference files for some steps, the Data Quality arrays for some steps are stored as 8-bit integers to conserve memory. Only the flags actually used by a reference file are included in its DQ array. The meaning of each bit in the DQ array is stored in the DQ_DEF extension, which is a binary table having the following fields: Bit, Value, Name, and Description.

Table 1. Flags for the PIXELDQ and GROUPDQ Arrays (Format of DQ_DEF Extension)

Bit	Value	Name	Description
0	1	DO_NOT_USE	Bad pixel. Do not use.
1	2	SATURATED	Pixel saturated during exposure
2	4	JUMP_DET	Jump detected during exposure
3	8	DROPOUT	Data lost in transmission
4	16	RESERVED
5	32	RESERVED
6	64	RESERVED
7	128	RESERVED
8	256	UNRELIABLE_ERROR	Uncertainty exceeds quoted error
9	512	NON_SCIENCE	Pixel not on science portion of detector
10	1024	DEAD	Dead pixel
11	2048	HOT	Hot pixel
12	4096	WARM	Warm pixel
13	8192	LOW_QE	Low quantum efficiency
14	16384	RC	RC pixel
15	32768	TELEGRAPH	Telegraph pixel
16	65536	NONLINEAR	Pixel highly nonlinear
17	131072	BAD_REF_PIXEL	Reference pixel cannot be used
18	262144	NO_FLAT_FIELD	Flat field cannot be measured
19	524288	NO_GAIN_VALUE	Gain cannot be measured
20	1048576	NO_LIN_CORR	Linearity correction not available
21	2097152	NO_SAT_CHECK	Saturation check not available
22	4194304	UNRELIABLE_BIAS	Bias variance large
23	8388608	UNRELIABLE_DARK	Dark variance large
24	16777216	UNRELIABLE_SLOPE	Slope variance large (i.e., noisy pixel)
25	33554432	UNRELIABLE_FLAT	Flat variance large
26	67108864	OPEN	Open pixel (counts move to adjacent pixels)
27	134217728	ADJ_OPEN	Adjacent to open pixel
28	268435456	UNRELIABLE_RESET	Sensitive to reset anomaly
29	536870912	MSA_FAILED_OPEN	Pixel sees light from failed-open shutter
30	1073741824	OTHER_BAD_PIXEL	A catch-all flag