This document provides instructions on running the Roman Science Calibration Pipeline (referred to as “the pipeline”) and individual pipeline steps.

Reference Files

Many pipeline steps rely on the use of reference files that contain different types of calibration data or information necessary for processing the data. The reference files are instrument-specific and are periodically updated as the data processing evolves and the understanding of the instruments improves. They are created, tested, and validated by the Roman Instrument Teams. They ensure all the files are in the correct format and have all required attributes. The files are then delivered to the Reference Data for Calibration and Tools (ReDCaT) Management Team. The result of this process is the files being ingested into the Roman Calibration Reference Data System (CRDS), and made available to the pipeline team and any other ground subsystem that needs access to them.

Information about all the reference files used by the Calibration Pipeline can be found at Reference File Information, as well as in the documentation for each Calibration Step that uses a reference file.


CRDS reference file mappings are usually set by default to always give access to the most recent reference file deliveries and selection rules. On occasion it might be necessary or desirable to use one of the non-default mappings in order to, for example, run different versions of the pipeline software or use older versions of the reference files. This can be accomplished by setting the environment variable CRDS_CONTEXT to the desired project mapping version, e.g.

$ export CRDS_CONTEXT='roman_0017.pmap'

Within STScI, the current storage location for all Roman CRDS reference files is:


Running From the Command Line

Individual steps and pipelines (consisting of a series of steps) can be run from the command line using the strun command:

$ strun <pipeline_name, class_name, or input_file>

The first argument to strun must be one of either a pipeline name, python class of the step or pipeline to be run. The second argument to strun is the name of the input data file to be processed.

For example, the Stage 1 pipeline is implemented by the class romancal.pipeline.ExposurePipeline. The command to run this pipeline is:

$ strun romancal.pipeline.ExposurePipeline r0008308002010007027_06311_0019_WFI01_uncal.asdf

Pipeline classes also have a pipeline name, or alias, that can be used instead of thefull class specification. For example, calroman.pipeline.ExposurePipeline has the alias roman_elp and can be run as

$ strun roman_elp r0008308002010007027_06311_0019_WFI01_uncal.asdf

Exit Status

strun produces the following exit status codes:

  • 0: Successful completion of the step/pipeline

  • 1: General error occurred

  • 64: No science data found

Input and Output File Conventions

Input Files

There are two general types of input to any step or pipeline: references files and data files. The references files, unless explicitly overridden, are provided through CRDS.

Data files are the science input, such as exposure ASDF files. All files are assumed to be co-resident in the directory where the primary input file is located.

Output Files

Output files will be created either in the current working directory, or where specified by the output_dir parameter.

File names for the outputs from pipelines and steps come from three different sources:

  • The name of the input file

  • As specified by the output_file parameter

Regardless of the source, each pipeline/step uses the name as a base name, onto which several different suffixes are appended, which indicate the type of data in that particular file. A list of the main suffixes can be found below.

The pipelines do not manage versions. When re-running a pipeline, previous files will be overwritten.

Individual Step Outputs

If individual steps are executed without an output file name specified via the output_file parameter, the stpipe infrastructure automatically uses the input file name as the root of the output file name and appends the name of the step as an additional suffix to the input file name. If the input file name already has a known suffix, that suffix will be replaced. For example:

$ strun romancal.dq_init.DQInitStep r0008308002010007027_06311_0019_WFI01_uncal.asdf

produces an output file named r0008308002010007027_06311_0019_WFI01_dq_init.asdf.

See Pipeline/Step Suffix Definitions for a list of the more common suffixes used.


All pipelines and steps have parameters that can be set to change various aspects of how they execute. To see what parameters are available for any given pipeline or step, use the -h option on strun. Some examples are:

$ strun roman_elp -h
$ strun calroman.dq_init.DQInitStep -h

To set a parameter, simply specify it on the command line. For example, to have roman_elp save the calibrated ramp files, the strun command would be as follows:

$ strun roman_elp r0008308002010007027_06311_0019_WFI01_uncal.asdf --save_calibrated_ramp=true

To specify parameter values for an individual step when running a pipeline use the syntax --steps.<step_name>.<parameter>=value. For example, to override the default selection of a dark current reference file from CRDS when running a pipeline:

$ strun roman_elp r0008308002010007027_06311_0019_WFI01_uncal.asdf

Universal Parameters

The set of parameters that are common to all pipelines and steps are referred to as universal parameters and are described below.

Output Directory

By default, all pipeline and step outputs will drop into the current working directory, i.e., the directory in which the process is running. To change this, use the output_dir parameter. For example, to have all output from roman_elp, including any saved intermediate steps, appear in the sub-directory calibrated, use

$ strun roman_elp r0008308002010007027_06311_0019_WFI01_uncal.asdf

output_dir can be specified at the step level, overriding what was specified for the pipeline. From the example above, to change the name and location of the dark_current step, use the following

$ strun roman_elp r0008308002010007027_06311_0019_WFI01_uncal.asdf

Output File

When running a pipeline, the stpipe infrastructure automatically passes the output data model from one step to the input of the next step, without saving any intermediate results to disk.

Pipeline/Step Suffix Definitions

However the output file name is determined (see above), the various pipeline modules will use that file name, along with a set of predetermined suffixes, to compose output file names. The output file name suffix will always replace any known suffix of the input file name. Each pipeline module uses the appropriate suffix for the product(s) it is creating. The list of suffixes is shown in the following table. Replacement occurs only if the suffix is one known to the calibration code. Otherwise, the new suffix will simply be appended to the basename of the file.



Uncalibrated raw input


DQ initialization


Saturation detection


Linearity correction


Dark current


Jump detection


Corrected ramp data


Optional fitting results from ramp_fit step


Assign WCS


Flat field


Photometric calibration


Calibrated image