Introduction to Combined Calibrations Generation Procedure

Overview

This procedure describes how to execute the SAL Script to take individual calibration frames (biases, darks, and flats) and verify them via the cp_verify package for LATISS or LSSTComCam on the ScriptQueue from the LSST Operations and Visualization Enviroment (LOVE) at the Summit.

The script will have the option to:

  • command the instrument to take a number of individual calibrations frames:

    • biases

    • darks

    • flats

  • call the corresponding Rubin Science Pipelines calibration generation pipetask to produce combined biases, combined darks, combined flats, defects, and Photon Transfer Curves (PTCs) via the OCS-Controlled Pipeline System (OCPS),

  • verify the images taken using as reference the calibration generated in the previous step via the generate_calibrations boolean parameter in the configuration file (this mode is referred to as “internal verification”; see the package cp_verify, and the technical notes DMTN-101 and DMTN-222), or using pre-existing calibrations that are usually located in the LATISS/calib or LSSTComCam/calib standard calibration collections (this mode is referred to as “external verification”), and

  • automatically certify the newly-generated combined calibration (if generate_calibrations is set to True) with a given range of validity dates (usually one day).

The verification step is currently only implemented for biases, darks, and flats. In order to run cp_verify, the verification pipetask uses as input individual images and the combined image for a particular calibration type as a reference. This reference combined image may already exist in the default calibration collection LATISS/calib or LSSTComCam/calib (a location that can be changed via the input_collections_verify_bias and similar parameters), or, the user can indicate the script to generate a new combined calibration from the individual images taken via the generate_calibrations parameter. The former is known as external verification, and the latter as internal verification. The two verification modes are designed to answer slightly different questions using the same tools; for external verification, the question is “are the data taken with the camera consistent with what they were in the recent past?”. This covers stability ranges on the day/week/month time scales. Internal verification asks “are the data taken with the camera consistent with themselves?”, covering stability ranges on the minute/hour level. By default, the script will run in external verification mode.

For at least one type of test (as defined in the sections of DMTN-101), if the majority of tests fail verification in the majority of detectors and the majority of exposures, then the script will terminate after calculating these verification statistics. If generate_calibrations is True, the calibration will not be certified into the calibration_collection collection. The configuration parameters number_verification_tests_threshold_bias, number_verification_tests_threshold_dark, and number_verification_tests_threshold_flat will be used to define thresholds to decide whether the calibration will pass verification and should be certified or not. Currently, verification is only implemented for BIAS, DARK, and FLAT calibration types. If the configuration parameters do_defects and do_ptc are set to True, verification will be skipped for the DEFECTS and PTC calibrations and they will be automatically certified.

The script currently has the option (via the script_mode parameter in the configuration options) to:

  • work with only biases (including talking the exposures and optionally generating and verifying a combined calibration),

  • work with biases and darks, and

  • work with biases, darks, and flats.

These options are constrained by the fact that the generation or construction of one calibration depends on the existence of the previous one (i.e., to generate a combined dark, a combined bias is necessary, and to generate a flat, a combined dark and a combined bias are necessary). If generate_calibrations is True, calibrations will eventually end up in the collection specified by the calib_collection configuration parameter and, if certified, will have a validity span range from certify_calib_begin_date to certify_calib_end_date.

Calibration generation from the images taken can also be skipped by setting generate_calibrations to False. This will speed up the execution time of the script, and subsequent tasks (for example, verification tasks or the PTC construction task) will look for necessary calibrations in their input collections (whose default is the standard calibrations collection: LATISS/calib or LSSTComCam/calib).

If desired, defects can be constructed from darks and flats (if do_defects=True), and a PTC per detector per amplifier constructed from the flats (if do_ptc=True). Note that the PTC assumes that a sequence of flat pairs has been taken, each pair taken at the same exposure time. In both cases, script_mode must be set to BIAS_DARK_FLAT.

For more information about calibrations production (including verification and certification), please consult the Constructing Calibrations documentation.

See also:

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This procedure was last modified on Nov 19, 2024.