1.105. mkOffSmooth

Full Name: herschel.hifi.pipeline.generic.MkOffSmoothTask
Alias: mkOffSmooth
Type: Java Task - Java Task
Import: from herschel.hifi.pipeline.generic import MkOffSmoothTask
Category

HIFI/Pipeline/Level 1 Pipeline

Description

Calibrates a baseline by processing the measurements of an OFF position in sky.

The following steps are carried through:

  • First, the OFF datasets are identified within the observation: type 'science' and 'isLine' false.

  • Second, the OFF datasets are smoothed. By default, a Gaussian smoothing filter is used and different alternatives are available to specify the smoothing width (parameters width, calibration, params or a default of 10 MHz). The smoothing operation is delegated to the Smooth-operation of the spectrum toolbox (see {@link herschel.ia.toolbox.spectrum.SmoothSpectrum}). Instead of applying a smoothing kernel (see the parameter filter, a polynomial fitting can be applied (see the mode-parameter for further details).

  • Finally, the smoothed measurements included in a OFF dataset are averaged. This means that the original number of spectra included in the OFF dataset is reduced to one (on a per dataset basis). In this way, for each dataset, associated with a particular phase in the observation, one baseline is obtained. This baseline is included in one of the datasets of the resulting calibration product - the dataset with the same group id. The time stamp of the single baseline is defined as the average of the observation times of the measurements included in the OFF dataset at the input level.

The baselines included within these datasets are ordered in observation time.

API details

Properties

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

The input data.

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

The calibration product with the baselines - for each LoSetting a different Spectrum2d dataset is provided.

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

Pipeline configuration parameters that can be passed to the task.

String mode [INPUT, OPTIONAL, default=default value filter]

Set the mode by which the baseline should be calculated ('avg' / 'filter' / 'fitter'). Note that 'avg' computes just an average whereas with 'filter' and 'fitter' the spectra are averaged (on a per dataset basis) and smoothed.

String filter [INPUT, OPTIONAL, default=default value "Gaussian"]

Set the type of filter when adoopting the "filter" mode ('Gaussian' / 'box').

String fitter [INPUT, OPTIONAL, default=no default value]

The type of fitter to be used when using mode='fitter' (only 'polynomial' is supported at the moment).

Integer degree_pol [INPUT, OPTIONAL, default=no default value]

Degree of the polynomial to be fitted.

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

The width (expressed in units as specified by the unit parameter) used for smoothing (when mode='filter'). If a negative or no width is specified, the width is looked up, if available, from the calibration tree (see calibration parameter) or set to 10.0 MHz. For Gaussian smoothing schemes, this width is divided by a factor 3.3 to transform it into a standard deviation (note that the width parameter of the smooth operation in the spectrum toolbox is interpreted as the standard deviation of the smoothing kernel). The smoothing width is included in the meta data of the CalOffBaseline-product (once it is created). In a former version (up to version 6.0), a positive width was determined from the number of ON and OFF data frames found in the timeline product. In this case, the width is equal to the ratio of the number of ON scans divided by the number of OFF scans rounded to the nearest integer.

String widthUnit [INPUT, OPTIONAL, default=no default value.]

Specify the unit the width is expressed in. The default is pixels, i.e. specify the width in number of pixels. Other values should be compatible with the unit specified for the wave scale (eg width in GHz and wave scale unit in MHz is ok but width in "cm" and wave scale unit in MHz is not).

MapContext calibration [INPUT, OPTIONAL, default=no default value]

Reference to calibration tree from which the smoothing width(s) is obtained.

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

Parameter to specify whether the calibration tree should be used as primary source of information. It plays a role for task parameters that can explicitly be set as task parameter value (here, for the width-parameter) or, alternatively, retrieved from the calibration tree (see parameter calibration). If useCalTree=True but no reference to the calibration tree is provided the width parameter is used.

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

If set to True no baseline is calculated.

See also

History

  • 2011-07-11 - melchior: History added.
  • 2011-08-14 - melchior: Renamed to MkOffSmoothTask.