Catalogs

  Two types of catalogs can be used by OBS _E :

a)

The source catalog which contains the basis system, source positions, and velocities. The search key is the source name, and the first match is extracted. The source catalog is used by the SOURCE command.

b)

The line catalog which contains the rest frequencies of spectral lines.

The search key is the name of the spectral line. In contrast to OBS at the 30-m MRT, all characters of the line name have to be given. The line frequency is extracted by the LINE command.

Both catalogs have the default file extension .CAT. Default catalogs are loaded at start up. If the item of interest is to be extracted from a different catalog by either of the commands SOURCE or LINE, the appropriate command should be accompanied by the adverb CATALOG. If a new catalog is to be used as the subsequent default, type,

OBSE >

SET_DEFAULT CATALOG_C < source-catalog filename > or

OBSE >

SET_DEFAULT CATALOG_L < line-catalog filename >

respectively.

The SOURCE Catalog

 

The command SOURCE transfers the source and catalog names to the OBSINP SOUR command. There, the source catalog is scanned sequentially for the first matching source name, which coincides in his first characters with the characters typed in.

Rules for preparing a catalog file are:

a)

Lines beginning with an exclamation mark (!) are taken as comments.

b)

Only one source per line, but commands for one source can extend to more than one line.

c)

Individual commands on a line are separated by a semi-colon (;).

d)

A line beginning with COMMON: defines commands that apply to all following entries until a new COMMON: or INDIVIDUAL: statement is encountered.

e)

A line beginning with INDIVIDUAL: defines commands that may be set for each following source seperately or else set to zero until another COMMON: or INDIVIDUAL: statement is encountered.

f)

A source entry must begin with a SNAM < source-name > statement, because the < source-name > is the key-string by which the search in the catalog is conducted. However < source-name > can be a list of alternative names seperated by blank characters.

In general, the source name, the basis system, the longitude, latitude and source velocity are extracted from the catalog. Details of this, and of preparing a source catalog, are given in the OBSINP manual. A sample catalog can be found in MPI$OBS:CATALOG_C.CAT. Due to the sequential search, we advise not to use too large a catalog, but to extract a reduced source list from a large catalog, and use this as the default catalog during your observing session.

EXAMPLE: for a source catalog:

INDIVIDUAL: SNAM SLAM SBET
COMMON: SBAS = 1; VHEL = 0.0;
SNAM= 0420-014 ; SLAM= 04 20 43.54 S; SBET= -01 27 28.7;
SNAM= 1226+023 3C273 ; SLAM= 12 26 33.25 S; SBET= 02 19 43.3;

etc. ...

NOTE: The first source in the catalog with an entry for SNAM containing the character string that matches the typed-in string will be taken. This can result in reading the wrong entry, if the order in the catalog is not respected. For example, suppose a catalog containing the following entries:
SNAM = 3C84; ....
SNAM = 3C8 ; ....
Then the command ''SOURCE  3C8'' would read in the source 3C84 instead of the wanted 3C8, as the string ''3C8'' is first encountered in the line with 3C84.
In a catalog the shorter source names have to be placed fist, if their initial string agree.

The LINE Catalog

 

If just a line name is present in the command LINE, the line catalog is searched for a perfect match between the name in the command and the name in the catalog. Then the frequency, possibly the side band, and perhaps a fixed frequency indicator are taken from the line catalog. A sample catalog can be found in MPI$OBS:CATALOG_L.CAT.

NOTE: The rules for the line catalog differ from those for the source catalog.

Rules for the line catalog:

a)

Information has to be on a single line. Letters are converted to UPPER CASE, as are the letters of the name in the LINE command.

b)

The line name has to be the first item of the line, but it can be preceded by blanks or a < TAB > . The frequency must be separated by a blank or a < TAB > .

c)

THz, GHz (default), MHz and kHz are recognized after the frequency, as are USB and LSB and the combination FIX. The sequence is irrelevant.

d)

The rest of the line can be used for comments. These should be preceded by an exclamation mark (!).

EXAMPLES :

		 EFFELSBERG_2.8_CM  10550.0 MHz  USB 		! center frequency of the 2.8 cm RX
		E3.6_cm 8.665650 FIX USB 		 ! technical frequency for 3.6 cm RX