Documentation on atmos

Task: atmos
Purpose: Generate ATCA-style mosaic file.
Categories: uv analysis

        ATMOS takes a list of sources (with RA and DEC), sorts them into
        an order to minimise the slew time between the sources, and then
        writes out an ATCA-style mosaic file which can be used by the
        ATCA on-line system to execute a mosaic observation.

        In the mosaic file, the cycles spent on each source is adjusted
        to account for the slew time needed to reach each source.

        NOTE:
        * ATMOS assumes the ATCA does not have wrap limits. It is
        conceivable that the antennas might have to do a pirouette in the
        middle of a mosaic block to move from north to south wrap (or visa
        versa). This will foul up all of ATMOS's calculations.

        * It does not appear that mosaicing is supported in anything but
        J2000 coordinates. All coordinates here should be in J2000.

        * You must give "sched" a reference position (the positions
        in the mosaic file generated by ATMOS will be relative to this
        position). ATMOS uses the position of the first source as the
        reference position.

Key: source
        A text file giving a list of sources. Each line of the file contains
          name ra dec
        The source name cannot contain blanks. RA and DEC are given as three
        numbers, being hh mm ss (for RA) and dd mm ss (for DEC).

        If the source name ends in "C", it is assumed to be a calibrator.
        ATMOS assumes that sources follow their calibrator -- the rearrangement
        ensures that this continues to be so. 
        Note that, for calibrators in a mosaic file, the on-line imaging
        software (CASNAP and friends) require names of calibrators to be 10
        characters long and end in a "C".

        Note that there must be at least two sources in the source list, and
        that the second source must not be a calibrator.

Key: lst
        Start time, given either in the format hh:mm:ss or decimal
        hours. The default is 0:00

Key: out
        Output mosaic text file. Default is mosaic.mos

Key: cycles
        Number of cycles to spend on-source at each source. Default is 2.

Key: interval
        Integration cycle time. Default is 15 seconds.

Key: origin
        The output mosaic file stores positions as an offset from
        some position. You have to give this value in your sched file.
        The `origin' parameter is used to set this position in ATMOS.
        It is an RA and DEC, in the format hh:mm:ss,dd:mm:ss, or decimal hours
        and decimal degrees). The default is the position of the first
        source in the list. NOTE: The on-line system always slews to the
        origin before it starts executing a mosaic. Consequently you
        reduce slewing time by using the default.

Key: ref
        This gives the name, RA and DEC where the antennas are pointing
        before the mosaic sequence is executed (the format for RA is
        hh:mm:ss, or decimal hours; and for declination is dd:mm:ss, or
        decimal degrees). The default is the RA and DEC of the first
        source to be observed (i.e. already on source).