Faint Object Spectrograph: dataset description

During the pipeline calibration, datasets consisting of

a Standard Header Packet (SH),
a Unique Data Log (UL),
a Science Data file (D0),
an associated set of Data Quality files (Q0, XQ, Q1)
a Science Trailer Line file (D1)
and a Science Header Line file (X0)

are created for the Faint Object Spectrograph.

These data sets are used as input to the standard calibration program, CALFOS, which produces a new set of calibrated data files:

a calibrated wavelength file (C0)
a calibrated flux file (C1)
a propagated statistical error file (C2)
an output data quality file (CQ)
a special statistics file (C3)
five sets of intermediate calibrated output (C4, C5, C6, C7, C8)

All calibrated data file headers are a copy of the Science Data header with appropriate keywords containing updated values.

All files for a particular observation have the same root file name;
the type of data in each file is identified by its extension.

The format of all retrieved files from the ST-ECF archive is FITS.

File Type Short Name File Extension Short Description

Standard Header Packet SH shf.fits Telemetry values for engineering data (such as temperatures, currents and voltages at various points in the instrument), spacecraft operation data (such as target position and spacecraft orbit), and some FOS-unique data (which are dependent on the on-board processing used for a given observation and include error flags associated with the mode II target acquisition).

Unique Data Log UL ulf.fits Mechanism control blocks used to control the entrance aperture, entrance port, polarizer, and filter and grating wheel assembly. The UL also includes instrument configuration and exposure parameters.

Science Header Line X0 x0f.fits It is a one-dimensional array with a length equal to a line of science data. It contains a copy of the uppermost words of the UDL data.

Science Data file D0 d0f.fits It contains single-precision floating-point values representing the number of detected counts accumulated for each pixel. The number of data elements in the one-dimensional science data array depends on the observation mode. Specifically, the number of data elements is based on the number of channels used, whether comb-addition is used, the number of steps, the number of substeps, the number of Y steps and the number of repeats ('slices' or 'bins').

Science Trailer Line STL d1f.fits It is a one-dimensional array containing the number of measurements rejected from the comb-addition steps, X substeps, Y steps, and repeats. The rejection is controlled by a threshold value, which is indicated in the UDL header as the keyword YNOISELM.

Science Data Quality file Q0 q0f.fits It contains flags for bad or suspect data in the corresponding data file.

Science Trailer Line Data Quality file Q1 q1f.fits It contains flags for bad or suspect data in the corresponding data file.

Science Header Line Data Quality file XQ xqf.fits It contains flags for bad or suspect data in the corresponding data file.

Calibrated Wavelength file C0 c0.fits It contains the single-precision floating-point calibrated wavelengths corresponding to each element of the science data.

Calibrated Flux file C1 c1.fits It contains the single-precision floating-point calibrated fluxes.

Propagated Statistical Error file C2 c2.fits It contains a measure of the statistical errors of the original data values; this file is calibrated in lock-step with the Science Data file. Errors caused by sky and background subtraction are ignored.

Output Data Quality file CQ cq.fits It flags bad pixels values in the Calibrated Wavelength and Flux files. The files retain the information in the input data quality files (although change the values) and flag problems detected in the calibration process. Good data values are still assigned a data quality value of zero.

Special Statistics file C3 c3.fits It is produced for the special ground software modes. In the rapid-readout mode the file contains total flux, integrated over all pixels for each readout, and the associated statistical errors.
In the time-resolved mode the file contains the average object spectrum, the difference of each slice (repeat) from the average, and the propagated statistical errors.
In the spectropolarimetry mode the file contains the four Stokes parameters, the linear polarization, the circular polarization, the polarization angle, and the error estimates for each of these parameters. These polarimetric quantities are provided for each pass direction, for the combined spectra, and for the combined spectra after correction for interference effects in the polarimeter.

Intermediate Calibrated Output files C4, C5, C6, C7, C8 c4-8.fits These 5 sets of intermediate files are dumped by CALFOS. These are: count-rate (C4), flat-fielded object spectra (C5), flat-fielded sky spectra (C6) (only if obtained by the observation), background spectra (C7), and flat-fielded object spectra with smoothed-sky spectra subtracted (subtracted form the flat-fielded object spectra prior to flux conversion if the sky is observed) (C8).

File Type	Short Name	File Extension	Short Description
Standard Header Packet	SH	shf.fits	Telemetry values for engineering data (such as temperatures, currents and voltages at various points in the instrument), spacecraft operation data (such as target position and spacecraft orbit), and some FOS-unique data (which are dependent on the on-board processing used for a given observation and include error flags associated with the mode II target acquisition).
Unique Data Log	UL	ulf.fits	Mechanism control blocks used to control the entrance aperture, entrance port, polarizer, and filter and grating wheel assembly. The UL also includes instrument configuration and exposure parameters.
Science Header Line	X0	x0f.fits	It is a one-dimensional array with a length equal to a line of science data. It contains a copy of the uppermost words of the UDL data.
Science Data file	D0	d0f.fits	It contains single-precision floating-point values representing the number of detected counts accumulated for each pixel. The number of data elements in the one-dimensional science data array depends on the observation mode. Specifically, the number of data elements is based on the number of channels used, whether comb-addition is used, the number of steps, the number of substeps, the number of Y steps and the number of repeats ('slices' or 'bins').
Science Trailer Line	STL	d1f.fits	It is a one-dimensional array containing the number of measurements rejected from the comb-addition steps, X substeps, Y steps, and repeats. The rejection is controlled by a threshold value, which is indicated in the UDL header as the keyword YNOISELM.
Science Data Quality file	Q0	q0f.fits	It contains flags for bad or suspect data in the corresponding data file.
Science Trailer Line Data Quality file	Q1	q1f.fits	It contains flags for bad or suspect data in the corresponding data file.
Science Header Line Data Quality file	XQ	xqf.fits	It contains flags for bad or suspect data in the corresponding data file.
Calibrated Wavelength file	C0	c0.fits	It contains the single-precision floating-point calibrated wavelengths corresponding to each element of the science data.
Calibrated Flux file	C1	c1.fits	It contains the single-precision floating-point calibrated fluxes.
Propagated Statistical Error file	C2	c2.fits	It contains a measure of the statistical errors of the original data values; this file is calibrated in lock-step with the Science Data file. Errors caused by sky and background subtraction are ignored.
Output Data Quality file	CQ	cq.fits	It flags bad pixels values in the Calibrated Wavelength and Flux files. The files retain the information in the input data quality files (although change the values) and flag problems detected in the calibration process. Good data values are still assigned a data quality value of zero.
Special Statistics file	C3	c3.fits	It is produced for the special ground software modes. In the rapid-readout mode the file contains total flux, integrated over all pixels for each readout, and the associated statistical errors. In the time-resolved mode the file contains the average object spectrum, the difference of each slice (repeat) from the average, and the propagated statistical errors. In the spectropolarimetry mode the file contains the four Stokes parameters, the linear polarization, the circular polarization, the polarization angle, and the error estimates for each of these parameters. These polarimetric quantities are provided for each pass direction, for the combined spectra, and for the combined spectra after correction for interference effects in the polarimeter.
Intermediate Calibrated Output files	C4, C5, C6, C7, C8	c4-8.fits	These 5 sets of intermediate files are dumped by CALFOS. These are: count-rate (C4), flat-fielded object spectra (C5), flat-fielded sky spectra (C6) (only if obtained by the observation), background spectra (C7), and flat-fielded object spectra with smoothed-sky spectra subtracted (subtracted form the flat-fielded object spectra prior to flux conversion if the sky is observed) (C8).

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Last update: Jul 31, 1996