1.15. checkFreqGrid

Full Name: herschel.hifi.pipeline.generic.CheckFreqGridTask
Alias: checkFreqGrid
Type: Java Task - Java Task
Import: from herschel.hifi.pipeline.generic import CheckFreqGridTask

HIFI/Pipeline/Level 1 Pipeline


Provide information about the frequency ranges observed in the timeline product

and forms groups of datasets with common LO settings. Furthermore, it computes suitable characteristics for measuring drifts in the grid of comb measurements. This information is provided in form of a quality product (of type {@link FreqRanges}).

Two scans are comparable, if

  • Number of sub-bands is identical.

  • LO settings are comparable.

Comparable datasets are grouped. For each group, a {@link TableDataset} is included in the {@link FreqRanges}-product. These datasets contain the keys of dataset that belong to the same group as meta data, the grid of subsequent comb-frequencies within the given group and the drift-measure between these comb-measurements. Care is needed when referencing the dataset keys in the meta data in case the datasets in the original timeline product are rearranged.

The drift measure is calculated by

  • first, computing for each sub-band the average difference between corresponding channel-frequencies of the subsequent comb measurements and

  • second, taking the maximum over the absolute values of the per sub-band measures computed in the first step.

  • Finally, this distance is divided by the distance in observation time.

The drift measure is reported in units Hz / sec.


  • Within each dataset, the frequency ranges are comparable. This step is resolved by the CheckDataStructure module.

  • Datasets with comparable data are subsequent in time.

  • In case of a FSwitch observation, it is assumed that in each dataset exactly two LoFrequencies are found.


Example 1: In HIPE:
checkFreqGrid = CheckFreqGridTask()
freqDrift = checkFreqGrid(htp=htp, tolerance=10)

API details


HifiTimelineProduct htp [INPUT, MANDATORY, default=no default value]

The timeline product (observation) to be analyzed.

Double tolerance [INPUT, OPTIONAL, default=no default value]

Tolerance (in Hz/sec) for the drift between successive comb measurements. If the tolerance is exceeded a warning is reported.

PipelineConfiguration params [INPUT, OPTIONAL, default=no default value]

Pipeline configuration parameters that can be passed to the task.

Boolean ignore [INPUT, OPTIONAL, default=no default value]

Flag to indicate whether the execution of the module should be ignored.

Boolean isFSwitch [INPUT, OPTIONAL, default=no default value]

Flag to indicate whether the given data should be treated as a FSwitch observing mode.

FreqRanges cal [OUTPUT, OPTIONAL, default=no default value]

The calibration/quality product provided as output.

See also


  • 2011-07-11 - melchior: : history added
  • 2011-07-19 - melchior: : refactoring of the code for solving HIFI-3834
  • 2011-08-08 - melchior: : HIFI-3834
  • 2011-08-14 - melchior: : renamed to CheckFreqGridTask