the external data set must have the following form
record 1:  title  (a80)
record 2:  information describing the table
columns
1-32  format of data entries  (a32)
33-34  kind of data in table  (i2)
=1 ut1-utc
=2 tai-ut1
=3  a1-ut1
36-42  julian day of first value in table  (i7)
44-50  julian day of last value in table  (i7)
52-53  maximum number of values per record  (i2)
55-56  interval in days betweeen tabular values  (i2)
58-72  units of values in seconds  (e15.7)
records 3-end:  data entries - format is read in record 2, but
must be of the form integer mjd folowed by up
to 12 integer values of ut1.  if a record is
short, the number of values in that record is
given in columns 79-80 (i2).

Compute the zonal tide corrections.  The coefficients are the
MERIT standards (USNO Circ. No. 167, p a11-2).  The coefficients
already include k/c=0.94; this is removed and the values from
kcf and kcm are then used.