The date on which the allsky 
-
coverage is to be calculated
is that on which observations began, i.e. the day of the start time. This
date is initially given a value equal to the epoch of launch, and must be
manually changed by the user when allsky is run. It is to be entered as
day month year (all integers) and the computer will verify that the input is
of the correct format. The year may be entered as the number of years after
1900, in other words, `1993' may be entered as `93'. Allsky will
recognize both entries, that is, `1993' or `93', `2013' or `113', etc..
Note that once a new value for the observation date is entered, the values of
and 
will take on slightly new values. This is
due to the fact that allsky incorporates a routine which takes into
account some orbital evolution effects. This routine performs a first order
calculation of the orbit evolution based upon the J2 coefficent of the Earth's
gravitational potential. This correction is not highly accurate, and the
cumulative errors will build up as the difference between the launch date and
the observations date becomes large.
The start ut is the universal time on which calculation of the -
coverage is to begin on the date given. The format for input of the start
time is hours minutes seconds (all integers). The hours are based on a 24 hour
clock, so that 2 pm should be entered as 14 0 0. Allsky will verify that
the time is given in an acceptable range and format. The stop ut is the
universal time on which the - coverage calculation should be stopped, in
other words, the time after UT0 on the start date. It
is handled in the same manner as the start ut time. If it is desired to
calculate the - tracks for more than 24 hours, the stop ut hour value
will be greater than 24; for example,
if the - coverage over 36 hours is desired starting at 03 00 00, the stop
time should be entered as 39 0 0. The default value is 0 for for both the start
and stop UT; in this case calculations are carried out for one orbital period.
The frequency at which data is collected is entered in MHz, and is set to 5000 MHz by default.
The ra step and dec step allow the user to specify the intervals
in right ascension and declination on the sky between successive -
coverage plots created by allsky. These should be entered in decimal
hours (ra step) and degrees (dec step).