The Special Requirements and their parameters are described below.

Fiducial Point Override

This requirement specifies an aperture for pointing (instead of the default aperture) for all exposure pointings in the Observation.

The target is placed at the fiducial point of the override aperture, but data are collected in all apertures regardless of this pointing change. Default apertures and pointing apertures are listed in the APT pointings report.

FIDUCIAL POINT OVERRIDE = APERTURE NAME

This requirement takes only one parameter (APERTURE NAME), which is required. Users may select any aperture defined in the Science Instrument Aperture File (SIAF). The SIAF defines apertures and their fiducial points. See Table for Apertures for a list of available apertures.

Settle Mode Exit Override

SETTLE MODE EXIT OVERRIDE = COARSE FINE

Upon exit from Settle Mode (after guide star acquisition), by default the attitude offset is set to zero. The SETTLE MODE EXIT OVERRIDE special requirement is used to set attitude offset to either COARSE or FINE instead upon Settle Mode exit.

Non Interruptible Passes

(added using the Survey Plan form)

This requirement specifies that each Pass in a survey plan step must execute without interruption. If a Pass is repeated, each Pass must not be interrupted, but interruptions are allowed between repeated passes. This special requirement has no parameters.

Orient Range

(added using the Survey Plan form)

This requirement limits the spacecraft orientation to the specified range of angles for each observation in a survey plan step.

ORIENT RANGE is specified by MIN-ANGLE   and MAX-ANGLE values.

Each angle indicates a rotation of the spacecraft V3 axis on the sky measured in a counterclockwise direction (North through East) around the target. Note that if the ORIENT RANGE crosses zero, the MIN-ANGLE value would be greater than the MAX-ANGLE value. For example: ORIENT RANGE = 350 TO 10 degrees specifies a 20 degree range across zero. MIN-ANGLE should be less than MAX-ANGLE otherwise.

In general, a larger range increases opportunities for scheduling.  If necessary, it is possible for MIN-ANGLE and MAX-ANGLE to be equal, thus restricting scheduling to a narrow time window when observations at that orient are possible.

Multiple ORIENT RANGE requirements may be applied to the same survey plan step to allow multiple acceptable angle ranges. For example:

ORIENT RANGE = MIN-ANGLE 1 TO MAX-ANGLE 1

ORIENT RANGE = MIN-ANGLE 2 TO MAX-ANGLE 2

ORIENT RANGE = MIN-ANGLE 3 TO MAX-ANGLE 3

Note for many observations, two angle ranges can have a 180 degree offset and still be schedulable. If this is possible (for greater scheduling flexibility), please specify the additional possible angles. It is also possible for the position angle region to be larger than 180 degrees

Between

(added using the Survey Plan form)

This requirement specifies that all visits of a survey plan step must start (but not necessarily end) between START-DATE and END-DATE   For example,  BETWEEN 14-SEP-2025 AND 21-SEP-2025 indicates that all visits of the survey plan step must be started after 14 September 2025 and before 21 September 2025.

Valid date formats are listed in the Table of Date formats. A date chooser is available in APT.

Multiple BETWEEN Special Requirements may be specified on a survey plan step.

For additional questions not answered in this article, please contact the Roman Help Desk at STScI.