11.5.1 COS Internal Calibration Targets

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Format definitions

Boldface type indicates the name of an APT parameter or a value for a parameter.

(red star) Black text indicates an important note.

Magenta text indicates available but unsupported parameters (requires prior approval from STScI).

Red text indicates restricted parameters (for STScI use only).

Brown text indicates text file parameters.

Items in brackets - <value> - are required values.

Items in square brackets - [<value>] - are optional.

Table 11.4: Internal Calibration Targets for COS


Target Name


Mode


Description

Aperture and Spectral Element

WAVE1

TIME-TAG

A wavelength calibration exposure for the grating and central wavelength being used for the spectroscopic science observations. The number of iterations must be 1.

Aperture = WCA, Spectral Element =
Any element from Table 11.5: COS Spectral Elements and Central Wavelengths2
except MIRRORA and MIRRORB

1 Exposures specified with the WAVE internal target will use the same calibration lamp configuration and exposure time as the automatic wave calibrations discussed below (based on the spectral element and central wavelength used). If Time_Per_Exposure is not specified as DEF, the specified exposure time will be used. To avoid overuse of the line lamps, the exposure time should not exceed 5 minutes.

Unless specifically requested in the Exposure Specification, a TIME-TAG Mode wavelength calibration will be automatically performed for each set of external spectrographic science exposures using the same spectral element, central wavelength, and OSM offset, including each subexposure of an exposure specification with optional parameter FP-POS=ALL. A wavelength calibration exposure will be added prior to the first such science exposure and after each subsequent science exposure if more than 40 minutes of orbital visibility time have elapsed since the previous wavelength calibration exposure. The calibration lamp configuration and exposure time will be based on the grating and central wavelength of the science exposure. For a detailed description of wavelength calibration exposures, see the COS Instrument Handbook. The automatic addition of wavecals may be disabled using the WAVECAL parameter.

2 DEF = same as the prior or subsequent spectroscopic science observation (i.e., if no element is specified, then the previously used one is assumed. MIRRORA or MIRRORB may be used in engineering programs.

Restricted Table 11.4 (cont)

Table 11.4: Internal Calibration Targets for COS

Target Name

Mode

Description

Aperture and Spectral Element

DEUTERIUM

(Restricted)

TIME-TAG

An exposure taken with the deuterium flat-field lamp. The number of iterations must be 1.

Aperture = FCA, Spectral Element = Any element from Table 11.5: COS Spectral Elements and Central Wavelengths except MIRRORA and MIRRORB

DARK (Restricted)

TIME-TAG

only

An exposure taken with the detector shuttered from external light to measure the detector dark current.

DEF3

3 DEF = no change from previous exposure. If the visit does not contain a prior COS exposure on a non-DARK target, STScI will assign a default aperture, spectral element and wavelength. For the COS/FUV configuration, the default aperture is PSA, the default spectral element is G130M, and the default central wavelength is 1222. For the COS/NUV configuration, the default aperture is PSA, the default spectral element is MIRRORA. DEF should be specified for the aperture and spectral element, while the central wavelength should be left blank.

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Related Links

11.5.2 COS Spectral Elements and Central Wavelengths
11.5.3 COS Apertures
11.5.4 COS WAVECAL Exposure Parameters
11.5.5 COS Coordinate System




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Change Log

Version Cycle 29 May 2021

      Worked on correctinos from the COS team in the restricted section.

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