Solar System Targets Position Level 1

The Solar System Targets form is used to specify moving targets in some JWST observations.  This article provides a description of the Level 1 specifications needed for the Astronomer’s Proposal Tool (APT).


 Format definitions...

Purple text indicates the parameter is Limited Access.

Boldface italics type indicates the name of an APT parameter or a value for a parameter.

(warning)Red text indicates restrictions on a parameter.

(red star) Black text indicates an important note.

Brown text indicates notes for the developers.

Green text indicates the name of the parameter used by Commanding.

Items in brackets - <value> - are required values.

Items in square brackets - [<value>] - are optional.

For the Level 1 position, specify your target in one of the following ways:

  1. STD = <object name>, where the name must be from the list of Solar System Standard Targets, or
  2. TYPE = <name>.

The TYPE = <name> target description allows the specification of non-standard targets in a variety of formats and must be the first entry in the field if it is used.

 Positional Parameters for TYPE = COMET

ParameterDefinition

Q = <value>

Perihelion distance, in AU

E= <value>

Eccentricity

I =<value>

Inclination, in degrees

O= <value>

Longitude of ascending node, in degrees

W = <value>

Argument of perihelion, in degrees

T = <value>

Time of perihelion passage, in TDB, TDT, or UTC

EQUINOX = <value>

either B1950, or J2000

EPOCH = <value>

Osculation date, in TDB, TDT, or UTC

[A1 = <value>]

Radial component of non-gravitational acceleration (AU/day2)

[A2 = <value>]

Component of non-gravitational acceleration lying in the orbital plane and parallel to the instantaneous velocity vector (AU/day2)

[A3 = <value>]

Component of non-gravitational acceleration directed perpendicular to the plane defined by A1 and A2 (AU/day2)


Positional Parameters for TYPE = ASTEROID

ParameterDefinition

A = <value>

Semi-major axis, in AU

E = <value>

Eccentricity

I = <value>

Inclination, in degrees

O = <value>

Longitude of ascending node, in degrees

W = <value>

Argument of perihelion, in degrees

M= <value>

Mean anomaly at EPOCH, in degrees

EQUINOX = <value>

J2000

EPOCH = <value>

Osculation date, in TDB, TDT, or UTC


For all cases, the required input data are described below. If the data are valid only over a specific period of time, then specify this time interval using the Solar System special requirements .

(red star) It is the responsibility of the observer to supply accurate orbital elements to STScI when specifying TYPE=COMET or TYPE=ASTEROID. Note that the requirement on how fast JWST can track a moving target is 30 milliarcsec/second.

Change log

Change log