FITSMERGE FITSMERGE converts a file in UVFITS format into the standard MERGE-format. The UVFITS format is very flexible, and FITSMERGE can only read some UVFITS files. In particular, the input file must contain data from a single source and a single IF. To transfer a merge file from one machine to another, use MERGEFITS on machine A (specifying INPUT and OUTPUT, defaulting other parameters); copy the FITS file to machine B (in binary mode), and on machine B run FITSMERGE (specifying INPUT and OUTPUT, leaving other parameters at default values). Example $ FITSMERGE INPUT = "0108.UVF" OUTPUT = "0108.MRG" LISTFILE = "fitsmerge.lis" TAI-UTC = 17 NOHISTORY / Parameters Parameters INPUT and OUTPUT must be specified; the others are optional. Parameter names may be abbreviated. End the list of parameters with a slash (/) or end-of-file. INPUT = "filename" : the name of the input FITS-format file, which must exist. OUTPUT = "filename" : a name for the new MERGE-format file. LISTFILE = "filename" : a name for a file to contain a record of the operation of FITSMERGE. This file contains a copy of the information sent to the standard output (the terminal, by default); if LISTFILE is not specified, the file is not created. TAI-UTC = m : specifies the Delta-AT correction, the difference TAI minus UTC, where TAI is International Atomic Time and UTC is Universal Coordinated Time. The time-tags on the data in the input file are assumed to be TAI, and are converted to UTC by subtracting TAI-UTC. By default (TAI-UTC not specified or specified as 0), FITSMERGE will apply the correct TAI-UTC by reference to a table of leap seconds. You should specify this parameter if you suspect that the TAI time in the input file may not be correct; e.g., specify the value of TAI-UTC used when the data were previously converted from UTC to TAI with, say, B2FITS or MERGEFITS. FITSMERGE Page 2 NOHISTORY : if this keyword is specified, the history records from the FITS file are not copied into the Merge file. WTPOWER WTFACTOR : the amplitude error bar in the merge-format file is calculated from the AIPS weight by err = (WTFACTOR/weight)**(1/WTPOWER) [inverse of MERGEFITS]. If the FITS file was created by MERGEFITS, these parameters are ignored and the values used in MERGEFITS are substituted. Weights and Error Bars When using FITSMERGE to read a FITS file created by MERGEFITS, you can ignore WTPOWER and WTFACTOR: FITSMERGE will use the values recorded in the FITS file header to reconstruct the original error bars. When using FITSMERGE to read a FITS file created by some other program, you need to pay careful attention to these parameters. For an AIPS file, usually WTPOWER should be 2 (weight proportional to inverse variance), but WTFACTOR is undefined. You may have to experiment with different values until you get error bars that look right. If you know precisely how the AIPS weights were calculated, it may be possible to determine the correct values for WTPOWER and WTFACTOR a priori. Limitations (some of these may be lifted in due course) 1. Up to 40 stations are accepted. 2. Closure phases are not computed; run ADDCLO after FITSMERGE if you need the closure phases. 3. The entire dataset must fit in memory. 4. For multichannel datasets (i.e., more than one frequency and/or more than one polarization), FITSMERGE extracts the first channel only. History Version 1.0: 1989 Aug 31 - (TJP). Version 1.01: 1989 Oct 26 - allow up to 20 axes. Version 1.02: 1990 Feb 6 - use SLA routine for TAI-UTC. Version 1.03: 1990 Feb 8 - recognize special "CIT" keywords. Version 1.04: 1990 Feb 22 - allow user to override TAI-UTC. Version 1.05: 1990 Feb 23 - add NOHISTORY keyword. Version 1.06: 1990 Mar 17 - accept AIPS 15OCT89 antenna tables. Version 1.07: 1990 May 22 - use RDFITS/RDFITC routines. Version 1.08: 1990 Jun 13 - avoid a divide-by-zero error. Version 1.09: 1990 Nov 13 - remove unused variables. Version 1.10: 1990 Nov 29 - standard Fortran. Version 1.11: 1991 Apr 23 - workaround for Sun Fortran bug. FITSMERGE Page 3 Version 1.12: 1991 Apr 25 - increase to 40 stations, multichannel. Version 1.13: 1991 May 15 - correct error in uvw coordinates. Version 1.14: 1991 Jun 21 - correct error in precession. Version 1.15: 1991 Aug 11 - decode weights.