XCOPRAW - Copernicus X-Ray Observations

Overview

Copernicus was the third satellite in the OAO program. It was launched the 21 august of 1972 and operated till 1981. The main instrument was an ultraviolet telescope with a spectrometer to measure interstellar absorption lines in the spectra of stellar objects. However it carried also an X-ray experiment provided by University College of London/MSSL consisted in 4 co-aligned experiments sensitive in the 1-10 keV energy range. This database accesses the raw FITS file containing data obtained from the UCL X-ray Experiment (UCLXE) package on board Copernicus.

Data Products

To each database record is associated one file. Each file includes data from all the experiments in the UCL X-ray Experiment (UCLXE) package. This consisted of four telescopes operating simultaneously. The main telescope was the 1-3 angstrom proportional counter which had a simple tube for collimation. The other three telescopes were Wolter type 0 grazing incidence mirrors with a dedicated detector. Two were proportional counters (3-9 angstrom and 6-18 angstrom) and the other a channel photomultiplier (CPM). The CPM suffers UV contamination and provided no useful data. The 3-9 and 6-18 angstrom telescopes became inoperable in July 1973 following the failure of the background shutter. A six Pulse Height Analyser (PHA) could be connected to any of the three proportional counters and used to extract spectral information. The basic time resolution was 62.509 seconds followed by 24 seconds dead time. This resulted in a 86.509 sampling time. It was possible to achive higher time resolution down to about 2 sec, with the usage of the J20 mode. This mode was used only in few occasions and was not scientifically useful.

The files accessible from this database are in FITS format. The layout consists of one extension bintable containing scientific and housekeeping data. The data are organized in each FITS file with the same content of the original file in its native format, where typically several files contribute to one observation.

Notes on Database Table

The native format of the original Copernicus UCLXE data did not contain the pointing position but only the source name and the observation log was not available in a suitable format when the FITS files were created. The coordinates in the fits file and within this database were mostly obtained by cross-correlating the object name with various catalogs available from HEASARC and SIMBAD and with the object name listed in the archive of the UV experiment, Princeton Experiment Package, on Copernicus (COP_PEP). In a few cases coordinates were assigned using the observation log.

A total of 131 files no matching object name were found in any of the catalogs searched. These entries can be identified by the parameter CATID1 and CATALOG set both to 'NONE' and the RA and DEC at 1950 equinox set to blank.

Offset observations respect to a source position have coordinates equal to the that source position (e.g. 3U1743-29PT3 is MX1743-29 or PUPPIS A (3) is PUPPIS A).

The objects 4U1658-58 and 2U2630-47 have been identified with 4U1658-48 (GX339-4) and 4U1630-47 since there is no record in the 4U catalog of 4U1658-58 and 2U2630-47 is a typo.

The original file structure contained an header followed by the data records. Two types of header record were present in the file storing different parameters. A string set to HEAD or SL identified the header type. The SL data are raster scan around a source position and the original SL header record did not contain either coordinates or object name. The RA_OBJ, DEC_OBJ, OBJECT keywords, in fits file with IDHEADER=SL, are retained from the HEAD observation immediately preceeding (in time) the current SL file.

The observation log was in a form of microfilm and not usable to extract easily coordinates. However we converted the microfilm to gif files (one gif for each microfilm frame). These files are available in the Copernicus FTP area in the HEASARC archive and they can be used to verify the exact pointing.

Parameters

Name
Object name given by the original data record.

RA
Right ascension associated to the catalog object name that matches best the object name in the data file. The catalog object name is stored in the parameter CATID1.

Dec
Declination associated to the catalog object name that matches best the object name in the data file. The catalog object name is stored in the parameter CATID1.

LII
Galactic longitude derived from RA and Dec.

BII
Galactic latitude derived from RA and Dec.

Catid1
This parameter contains the object name found in a catalog that matches best the object name in the data file. The parameter CATALOG contains the catalog or server name.

Catalog
This parameter contains the catalog (or server) name used to match the object name in the data file. The possible values are listed below.

     XRBCAT    catalog available at HEASARC
     VERON96   catalog available at HEASARC
     NGC2000   catalog available at HEASARC
     4UHURU    Forman et al., 1978 Ap.J.Supp.S., 38,357
     3UHURU    Giacconi et al., 1974 Ap.J.Supp.S.,27,37
     2UHURU    Giacconi et al., 1972 Ap.J. 178, 281
     BSC       catalog available at HEASARC
     HIC       catalog available at HEASARC
     HD        catalog available at HEASARC
     COP_PEP   Positions listed in the archive of UV experiment on Copernicus
               "Princeton Experiment Package"
     SIMBAD    using the name server
     ULC_OBS   ULC observation log

Head
Stored a string that indicates the header type in the original data. The allow value are "HEAD", "SL ", or "SLEW" and they indicates the following differences

     HEAD - Object name given in the header of the original file.
     SL   - No object name given
     SLEW - Object name is "SLEW".

Num_Rows
Number of rows in the data file.

Telapse
Time elapsed during observation (TELASPE = TSTOP - TSTART) given in seconds.

Start_Obs
Observation start date stored as a string.

End_Obs
Observation end date stored as a string.

Start_Time
Observation start stored as numerical value (browse SHF or W3browse MJD).

End_Time
Observation stop stored as numerical value (browse SHF or W3browse MJD).

Totcn13
Total counts in the 1-3 Angstrom detector. This is the sum of all counts for the 1-3 A detector in the file.

Totcn39
Total counts in the 3-9 Angstrom detector. This is the sum of all counts for the 3-9 A detector in the file.

Totcn618
Total counts in the 6-18 Angstrom detector. This is the sum of all counts for the 6-18 A detector in the file.

Totcncpm
Total counts in the CPM detector.This is the sum of of all counts for the CPM A detector in the file.

Avecn13
Average counts in the 1-3 A detector counts obtained as AVECN13 = TOTCN13/NUM_ROWS.

Avecn39
Average counts in the 3-9 A detector counts obtained as AVECN39 = TOTCN39/NUM_ROWS.

Avecn618
Average counts in the 6-18 A detector counts obtained as AVECN618 = TOTCN618/NUM_ROWS.

Avecncpm
Average counts in the CPM A detector counts obtained as AVECNCPM = TOTCNCPM/NUM_ROWS.

Avegc13
Average 1-3 A guard counts obtained as AVEGC13 = TOTGCN13/NUM_ROWS, where the TOTGCN13 is the total number of guard counts (not recorded in this database).

Avegc39
Average 3-9 A guard counts obtained as AVEGC39 = TOTGCN39/NUM_ROWS, where the TOTGCN39 is the total number of guard counts (not recorded in this database).

Avegc618
Average 6-18 A guard counts obtained as AVEGC618 = TOTGCN618/NUM_ROWS, where the TOTGCN618 is the total number of guard counts (not recorded in this database).

Tdiff_Mean
Time Difference between Rows Mean

Tdiff_Min
Minimun time difference between rows in the FITS file, for this entry, given in seconds (for internal use).

Tdiff_Max
Maximum time difference between rows in the FITS file, for this entry, given in seconds (for internal use).

Root
FITS filename root. Used to extract the file from W3browse. The files are named with the following convention uclYYDDDHHMM_h/s#### where

     ucl  -
     YY   - Year.
     DDD  - Day of year number.
     HH   - Hour.
     MM   - Minute.
     h/s  - "h" for HEAD record, "s" for SL or SLEW record.
     #### - Chronological file number.

Filename
FITS file location and name root used to extract the file from browse. The naming convention is uYYDDDDDD/uclYYDDDHHMM_h/s#### where

     u      -
     YY     - Year.
     DDDDDD - First three DDD day of earliest file second three last day or
              latest file in directory.
     ucl    -
     YY     - Year.
     DDD    - Day of year number.
     HH     - Hour.
     MM     - Minute.
     h/s    - "h" for HEAD record, "s" for SL or SLEW record.
     ####   - Chronological file number.

Contact Person

Questions regarding the XCOPRAW database table can be addressed to the HEASARC Help Desk.

Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:36:56 EDT