On-screen Parameters

See Figure on p. .

The date on which the - coverage tracks are 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 uvplot 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'. Uvplot 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 uvplot 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. Uvplot 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 right ascension (ra) of the source to be observed should be entered in decimal hours, and is assigned an initial value equal to the right ascension of the ascending node of the orbit plus six hours. The declination (dec) of the source to be observed should be entered in decimal degrees, and is assigned an initial value of sixty degrees.