11.5.3 COS Apertures
There are a few apertures available for HST's COS detectors, and this articles describes those apertures. |
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Format definitions
Boldface type indicates the name of an APT parameter or a value for a parameter.
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.
Valid COS apertures are listed in Table 11.7: COS Apertures. Science observations should use the PSA or BOA apertures. The BOA aperture is the same size as the PSA but contains a neutral-density filter that attenuates the source by a factor of ~200. The WCA is intended for wavelength calibrations using the WAVE target.
Table 11.7: COS Apertures
Aperture | Definition | Size | Usage |
PSA | Primary Science Aperture | 2.5 arc-seconds | Default science aperture |
BOA | Bright Object Aperture | 2.5 arc-seconds | Contains neutral density filter (ND2) for bright objects Not permitted for grating/wavelength combinations that default to lifetime position LP7 or LP10 ; those need to request use of LP4. |
WCA | Wavelength Calibration Aperture | 20 microns (dispersion) × 100 microns | Wavelength Calibrations |
Restricted FCA
Related Links
11.5.1 COS Internal Calibration Targets
11.5.2 COS Spectral Elements and Central Wavelengths
11.5.4 COS WAVECAL Exposure Parameters
11.5.5 COS Coordinate System