LISTs

The LISTs contain a set of properties for each event (or for each primitive instrument bin, see below). Their structure looks like:

        X_CORR               <LIST>
           DATA_ARRAY(N)        <_REAL>
           QUANTUM              <_REAL>    Scalar or vector
           UNITS                <_CHAR*80>
           FIELD_MIN            <_REAL>
           FIELD_MAX            <_REAL>
           DECREASING           <_LOGICAL>

Of these components, only DATA_ARRAY is mandatory, though FIELD_MIN and FIELD_MAX are required by binning software. Data type does not have to be _REAL, but it is wise to make the types of the numerical components consistent. Note that each LIST is in fact an NDF (containing only DATA_ARRAY, and possibly UNITS), hence a LIST can be used as input to many analysis applications, which will default the missing components such as axis information.

The contents of the various components are:

DATA_ARRAY - the actual list values. 
QUANTUM    - width of bins used to locate the data array values
             (i.e. quantum of measurement). Can either be the same
             for all events (scalar value) or given separately for
             each event (vector of values). Where QUANTUM is not
             specified it will be assumed by binning software to
             be 1 for integer data types, and 0 (i.e. 
             infinite instrumental precision) for _REAL data.
UNITS      - char*80 string giving data units.
FIELD_MIN  - minimum and maximum values of field
FIELD_MAX    over which the list data have been collected. (Note
             that this is not the same as the observed data range).
             Binning software requires these to be present. 
DECREASING - This is a flag which tells binning software to bin this
             axis in decreasing order (e.g. azimuth angle is usually
             treated in this way).

Note that FIELD_MIN and _MAX values correspond to the CENTRE values of the extreme primitive bins, not to their boundaries. Unlike ranges entered by users (see section 6) both _MIN and _MAX values are INCLUSIVE.

For some LISTs (e.g. TIMETAG, X_CORR, Y_CORR), the DATA_ARRAY values MUST be expressed as offsets from information in the HEADER. In this case the FIELD_MAX and _MIN values should also be expressed as offsets.

For example, consider a TIMETAG LIST. The values in DATA_ARRAY are offsets from BASE_TAI (in the HEADER). Hence if the observation starts at the time given by BASE_TAI and lasts for a total of OBS_LENGTH seconds, with a measurement quantum of size QUANTUM, then (remembering that FIELD_MIN and _MAX refer to the CENTRES of the extreme bins)

     FIELD_MIN = QUANTUM/2
     FIELD_MAX = OBS_LENGTH - QUANTUM/2