This article describes the parameters for Fixed Targets for the Roman telescope. 

Introduction 

A Roman Fixed Target consists of a specification of coordinates and other target parameters for use as the base pointing of an Observation. 

• All Fixed Targets specified in the program may be referenced in multiple Observations within the Program.
• Any modifications to a Target Specification are used in all Observations that reference that Fixed Target.
  

Fixed Target Identification Parameters

The Target Identification form for Fixed Targets includes 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 ranging from APT Range Field 1 TO 9999 ;  note that these can be changed by the user. 

Name 

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

Resolvable Name 

APT Parameter Field Resolvable Name is a name you provide for use by the Archive. Using a common name for the target (e.g. CRABNEBULA instead of NGC1952) can make a program more readable. Annotating the name (e.g. CRAB1, CRAB2) may be useful when sampling parts of an extended object. But these names are not as helpful for people searching the Archive. So the APT Parameter Field Resolvable Name is an optional second target name. Proposers and archival researchers use these names to determine whether Roman has observed a particular object. This facility will be most useful if the names supplied are resolvable with standard name resolvers such as NED or SIMBAD.  

APT Parameter Field Resolvable Name is not required, but if used must be 2 to 31 characters in length.

Category

APT Parameter Field Category - Each target must be assigned a single APT Parameter Field Category fromthe Table of Target Categories, and at least one descriptive keyword ( APT Parameter Field Description ), chosen from the appropriate tables.

APT Parameter Field Category is required and is selected from a list.

Description

APT Parameter Field Description - One to five keywords must be selected for each target. Descriptions are selected from a table depending on the selected APT Parameter Field Category (see the Table of Target Categories). APT Parameter Field Description is one of the fields used by archival researchers in searching through the Roman data archive; thus it is extremely important that the information be supplied by the observer who knows the intention for each target.

Fixed Target Coordinates Parameters

Target Coordinates for Fixed Targets include a number of parameters described below.

J2000 Coordinates (ICRS)

The right ascension ( APT Parameter Field RA ) and declination ( APT Parameter Field Dec ) for the target are required and 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.

Proper Motion 

Proper motion for the target may be specified with APT Parameter Field RA PM for right ascension and APT Parameter Field Dec PM for declination. At the time of the observation, the proper motion correction will be applied to the target coordinates (from the specified APT Parameter Field Epoch to the date of observation). The user must determine whether or not proper motion or parallax is significant.

• APT Parameter Field RA PM units may be mas/yr, arcsec/yr, or seconds of time/yr. 
• APT Parameter Field Dec PM units may be mas/yr or arcsec/yr.
• Both APT Parameter Field RA PM and  APT Parameter Field Dec PM may be left blank but if either one is entered, both are required.

Epoch

APT Parameter Field Epoch  is the the date of the target coordinates (either the date the target coordinates were measured or the date to which the target coordinates have been corrected using the proper motion).

• If proper motion has been specified for the target, APT Parameter Field Epoch of the target coordinates must also be specified. 
• APT Parameter Field Epoch  must be entered in a decimal year format (yyyy.nnn).

Annual Parallax

APT Parameter Field Parallax is the annual parallax of the target's position in arcsec/year.  As with proper motion, the user must determine if parallax is significant.   APT Parameter Field Parallax is applied to the target coordinates at the time of the observation. 

• APT Parameter Field Parallax may be left blank. The allowed range is APT Range Field 0.00 TO 0.08 arcsec/year.

Comments

Enter any comments about the target. Comments are stored with the target data within the program.

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