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40.1 Data Products and File Structures

There are five standard data formats for HSP data. They are listed in Table 40.1.


HSP Data Formats

Format

Description

BYTE

One-byte digital

WORD

Two-byte digital

LONGWORD (LWRD)

Three-byte digital

ANALOG (ALOG)

12-bit analog (in two bytes)

ALL

Three-byte digital plus two-byte analog

The Post-Observation Data Processing System (PODPS) pipeline calibration process produces datasets in Generic Edited Information Set (GEIS) format. The datasets contain a standard header packet, a unique data log, and one to four science data files (and corresponding data quality files). Each file contains an ASCII header file and a binary data file. Each of the files has the same rootname, and the type of file is designated by its suffix. The following table lists the description of the suffixes as determined by the data format and the mode.


HSP Data Files

Extension

File Contents

Raw Data Files

.shh/.shd

Standard header packet

.ulh/.uld

Unique data log

.d0h/.d0d

Science data, digital star

.d1h/.d1d

Science data, digital sky

.d2h/.d2d

Science data, analog star

.d3h/.d3d

Science data, analog sky

.q0h/.q0d

Data quality, digital star

.q1h/.q1d

Data quality, digital sky

.q2h/.q2d

Data quality, analog star

.q3h/.q3d

Data quality, analog sky

Calibrated Data Files

.c0h/.c0d

Calibrated digital star data

.c1h/.c1d

Calibrated digital sky data

.c2h/.c2d

Calibrated analog star data

.c3h/.c3d

Calibrated analog sky data

40.1.1 Standard Header Packet

The Standard Header Packet (SHP) contains the instrument engineering telemetry values, and other data from spacecraft operations. The telemetry values found in the SHP are observed values and may include quantities that are not controllable.

40.1.2 Unique Data Log

The Unique Data Log contains commanded values for various instrument settings. The UDL also contains data from the flight software.

40.1.3 Science Data Files

Science data are stored as single-precision floating point values. The results of the pipeline calibration are files containing the HSP count rates as a function of time. The number of files in the dataset depends on the mode and the data type. A single observation could generate up to eight separate data files. Science data files are identified by their suffixes as shown in Table 40.2.

40.1.4 Quality Mask Files

Each of the science data files has a corresponding quality file that contains single-precision floating point values. Good data values are identified in the file with a value of zero. An error at any pixel during the data capture process results in a non-zero value. HSP data quality flag values are listed in Table 40.3.


HSP Data Quality Flag Values

Flag Value

Description

0

Good data

1

Reed-Solomon decoding error

8

A/D converter saturation

16

Missing data

40.1.5 Calibrated Data Files

The HSP calibration program, calhsp, generates the calibrated file for each corresponding raw science data file. The calibrated and the raw data header files contain the same keywords, except the raw data are corrected for instrument signatures.


Note that the photometric sensitivity is poorly determined and the calibration correspondingly uncertain.

40.1.6 HSP Data Products

Generally, most HSP data are delivered from the Archive in FITS format. For large volume data samples, FITS format files may not be produced. In this case the delivered data remain in GEIS format.

40.1.7 HSP Keywords

Table 40.4 describes important HSP keywords. This table does not include all keywords that are found in all of the data headers.


HSP -Keywords

Keyword

Description

ROOTNAME

Root file name of the observation dataset

RA_TARG

Right ascension of target, in degrees (J2000)

DEC_TARG

Declination of target, in degrees (J2000)

MODE

Instrument mode (SCP, SSP, or ARS)

DETECTOB

Detector in use (0-5); object data

DETECTSK

Detector in use (0-5); sky data

APERTOBJ

Aperture in use-object data

APERTSKY

Aperture in use-sky data

DEADTIME

Deadtime correction

TRUE_CNT

Compute the true count rates

TRUE_PHC

Compute the true photocurrents

DATA_TYP

Data type (digital or analog)

DATA_SRC

Data source (star, sky, or area scan)

DATA_FMT

Data format (byte, word, lwrd, alog, or all)

TIMEBIAS

Instrument time bias (in seconds)

SAMPTIME

Time of integration (in seconds)

PT_EFFIC

Scaled point source cathode efficiency

EX_EFFIC

Scaled extended source cathode efficiency

DARKRATE

Scaled cathode dark rate

PRE_AMP

Scaled tube pre-amp contribution

HIGHVOLT

Scaled high voltage factor

TUBEGAIN

Scaled tube gain factor

DEADTM

Deadtime

CVCOFSET

Scaled CVC offset

EXPSTART

Exposure start time (modified Julian date)

EXPEND

Exposure end time (modified Julian date)

FILETYPE

shp, udl, or dst (digital sky); dsk (digital sky); ast (analog star); ask (analog sky); asd (area scan digital); or asa (area scan analog)

PTSRCFLG

Point source flag (P for point, or E for extended)



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