A Region Target is a array of RA/Dec coordinate pairs to fill a region of the sky. Each coordinate pair specifies where one Segment of the Pass Plan will be executed. Planning for the Region Target must be done externally to APT, taking into account segment dimensions, segment overlap, and orientation.

Region Target Definition Parameters

A Region Target  is defined using a number of parameters described below.

Number

APT Parameter Field Number  - Each target in your Program will be assigned its own unique number by APT but may be changed by the user (as long as it remains unique within the program). APT Parameter Field Number is required and may be from  APT Range Field 1 TO 9999

Name

APT Parameter Field Name  is a name you provide for the target within the Program. You must provide a unique name for a target. APT Parameter Field Name is required, must be 2 to 31 characters in length and only use letters, numbers, “.”, “+”, and “-”. No other characters are allowed including blanks.

Reference Position

The orientation of all segments in a Region Target is represented with respect to its APT Parameter Field Reference Position , specified as a single RA/Dec point. APT Parameter Field Reference Position is required and may be entered manually or automatically.

To add the APT Parameter Field Reference Position  automatically, click the Set Reference Position button. APT calculates the APT Parameter Field Reference Position as the center of all the Region Coordinates.

Right ascension ( APT Parameter Field RA ) and declination ( APT Parameter Field Dec )  must be entered as ICRS coordinates (International Celestial Reference System).

• APT Parameter Field RA may be entered in HMS format (hh mm ss.ssss), or as decimal degrees (ddd.dddd). Decimal numbers will be converted to HMS. 
• APT Parameter Field Dec may be entered in DMS format (dd mm ss.ssss) or as decimal degrees (ddd.dddd). Decimal degrees will be converted to DMS.

Planned Orient 

APT Parameter Field Planned Orient documents the spacecraft orientation assumed when planning the region target. Note that APT Parameter Field Planned Orient has no effect on the execution of the Observation of this Region Target. In order to control the orientation of the observations, use the APT Parameter Field Orient Range Special Requirement. APT Parameter Field Planned Orient is required.

Region Coordinates

The right ascension ( APT Parameter Field RA ) and declination ( APT Parameter Field Dec ) for the pointings necessary to cover the region are required and must be entered as ICRS coordinates (International Celestial Reference System). Note that a Region Target is not required to be geometrically continuous.

• APT Parameter Field RA may be entered in HMS format (hh mm ss.ssss), or as decimal degrees (ddd.dddd). Decimal numbers will be converted to HMS. 
• APT Parameter Field Dec may be entered in DMS format (dd mm ss.ssss) or as decimal degrees (ddd.dddd). Decimal degrees will be converted to DMS.

There are options to Add, Import, Export, Set Reference Position, Duplicate, Insert Above, and Remove.

Region Planner

One option for calculating the pointings necessary to cover the region is to use the Region Planner. The Region Planner allows the user to calculate pointings required to cover the region using segments of various sizes and at various orientation angles. 

• First define the desired region (any polygon) by supplying the right ascension ( APT Parameter Field RA ) and declination ( APT Parameter Field Dec ) of the vertices of the region to be covered. The order of the vertices can produce polygons of different shapes, so a small viewer is provided to support visual verification and iteration.
• Then supply the   APT Parameter Field Segment Width (arcmin), APT Parameter Field Segment Height (arcmin), APT Parameter Field Segment Orient (arcmin). The region will be automatically filled by these segments at a default orientation. Note that the tool starts with a default segment size, and returns to it each time the tool is opened.
• Select a APT Parameter Field Tiling Orient (inputs outside the legal values from APT Range Field 0.0 TO 360.0 will throw a APT Warning Warning ) by typing in a number or using the slider. A plot is provided which previews the number of tiles required to cover the region as a function of tiling orient.
• APT Parameter Field Execution Orient (inputs outside the legal values from APT Range Field 0.0 TO 360.0 will throw a APT Warning Warning ) can be adjusted by typing in a number or using the slider.  APT Parameter Field Execution Orient is the same as the APT Parameter Field Tiling Orient by default. When a different value is selected it allows you to preview any gaps in coverage that would occur if the region target was planned at the APT Parameter Field Tiling Orient yet executed at the APT Parameter Field Execution Orient

• Apply Plan to Target: once parameters have been optimized, click this button to generate the array of coordinates that define the Region Target.

• There are options to Add, Import, Export, Duplicate, Insert Above, Remove.
  
  

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