LET @name = @name UNION @nameor symbolically
LET @name = @name + @name
The union of two schedules is analogous to the union of two sets: the
resulting schedule contains every point contained in one or both of the
original schedules. Unions are useful primarily for determining intervals
during which at least one of two or more constraints are valid.
A graphical description of the UNION command is shown below.
Input schedule : --- --------- --------- - Input schedule : - ----- ----- ----- Output schedule : - --- --------------------- -----
In the following example, schedules OCC, ECL, and TRN contain intervals when
a satellite (Io) is occulted, eclipsed, and in transit. The union of OCC and
TRN yields a schedule containing intervals when the satellite is hidden by
Jupiter. The union of the resulting schedule with ECL yields a schedule
containing intervals when the satellite cannot be observed.
FIND OCC OCCULTATION OF IO
BY JUPITER
FROM EARTH
STEP SIZE 15 MINUTES;
FIND ECL ECLIPSE OF IO
BY JUPITER
FROM EARTH
STEP SIZE 15 MINUTES;
FIND TRN TRANSIT OF IO
ACROSS JUPITER
FROM EARTH
STEP SIZE 15 MINUTES;
LET BAD = OCC + ECL;
LET BAD = TRN + BAD;