OPHA is the parameter for OPTMODE=HAS that sets the desired hour angle at the reference station OPHASTA for this scan. If this parameter is not set, SCHED figures out how many scans there are on the source, when the source can first be seen (either because of elevation limits or experiment start time) and when it can last be seen. It then spaces the desired observation times evenly between those times.
The weight based on deviation from the desired hour angle is calculated using the formula:
TIMEWT=OPHAWT(JSCN)*(0.5+(1.0/PI)* ATAN(1.5*(TAPPROX-OPHAT(JSCN))/ OPHAWIDT(JSCN)))where OPHAT is OPHA converted to a time, TAPPROX is the proposed observe time of the next scan, and OPHAWT and OPHAWIDT are other SCHED input parameters. Note TAPPROX is likely to be adjusted slightly once the scan is chosen and full account of slew times is taken.
See the discussion of the possible optimization modes in the section on OPTMODE for more information on OPTMODE=HAS