Realtime Commanding Template Parameters

JWST's Realtime Commanding Template, available in the Astronomer’s Proposal Tool (APT), is used for Realtime commanding of JWST.

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.

The Realtime Commanding template is used for Realtime commanding of JWST in support of critical activities. These activities must occur during the command uplink periods of Deep Space Network (DSN) contacts. No other activities are allowed during this time period unless coordinated beforehand through the Realtime Commanding template.

An individual Realtime visit first executes slews and guide star acquisitions and then any preparation tasks which can take place prior to the start of the DSN contact. The Realtime commanding period starts after the scheduled start time of the DSN commanding uplink window. Optional cleanup tasks can also be executed if required.

The Special Requirements NO PARALLEL, REALTIME, REQUIRED, PCS MODE COARSE (if a target is chosen) or PCS MODE NONE (if target is NONE), and SPECIAL COMMANDING are implied for this template. Special Commanding is required so it will need sign-off by the Commanding team using OPGS. Otherwise, this visit cannot be added to the FLIGHT baseline, since the Special Commanding flag will prevent it from getting onto an OP until approved.

Note for developers: The SPECIAL COMMANDING text field is "Special Commanding Realtime Commanding".

The following parameters are used to define Realtime Commanding observations.

General Information
Observation Numberassign observation numbernumber
Observation Labelprovide observation labeltext
Observation Commentsprovide observation commentstext
Target Nameselect Target Namechoose from listfrom Target List
Special Requirementsspecify special requirementschoose from listif needed
Template specific information

Target Name

select target name

choose from list

from Target list

Science Instrumentselect science instrumentchoose from list
select aperturechoose from listif target is selected
Realtime Durationspecify Realtime Durationnumber
Handoff Window Durationspecify Handoff Window Durationnumber
Initial Setup Durationspecify Initial Setup Durationnumber
Cleanup Durationspecify Cleanup Durationnumber

General information  

The following parameters are generic to all templates, and are not discussed in this article: Observation Number,  Observation Label, Observation Comments, Target Name, and Special Requirements.

Target Name

Select the TARGET NAME [TBD] from the list of targets previously entered (see list of targets) if the observation is to be a "pointed internal"; or select NONE   if the observation is to inherit the attitude from the previously executed visit.  

Note for developer: Make NONE the default for Target Name.

Science Instrument


Specify the science instrument that is being used in the Realtime Commanding visit. If no science instrument is being used then select NONE.

Note for developer: If the Realtime Commanding visit is included in SEQ NON-INT observation list with EXCLUSIVE USE OF INSTRUMENT and the Science Instrument = NONE then APT should ignore the SCIENCE INSTRUMENT for the Realtime Commanding visit and not display an error.


Select an APERTURE if a Target Name was selected. Any legal value in the SIAF is allowed.

Note for developer: This is an expert user, so allowing any SIAF aperture should be fine, with no need to massage the name. Or we could come up with shorthands for the expected apertures, such as the Imager, MRS, NIRCam A and B, etc.

Realtime Duration

REALTIME DURATION [RTDURATION] specifies the maximum amount of time needed to complete the Realtime commanding. This duration must fall within a DSN uplink commanding window.

(warning) This value must be in the range 1 to 28800 seconds.

(warning)  If HANDOFF WINDOW DURATION is not specified, REALTIME DURATION must be greater than or equal to 1800.

Handoff window duration

HANDOFF WINDOW DURATION [RTHANDOFF] specifies the time during which the S&OC FOT must acknowledge taking observatory control. Failure to respond within this window results in the Realtime observation being skipped after any cleanup activities are completed. 

(warning)  This parameter is optional but if specified must be in the range 1 to 28800 seconds, and must be less than or equal to REALTIME DURATION

(warning)  If not specified, this parameter will default to thirty minutes (1800 seconds) by OSS scripts

Initial setup duration

INITIAL SETUP DURATION [INITDURATION] specifies the amount of time required to complete any initial setup activities; (warning)this value must be in the range 0 to 28800 seconds.

Cleanup duration

CLEANUP DURATION [CLEANDURATION] specifies the amount of time required to complete any cleanup activities; (warning)this value must be in the range 0 to 28800 seconds.

Change log

Version 4 (February 21, 2022)

  1. PROPINSTJWST-83399 Updated limits and diagnostics for Realtime Duration and Handoff Window duration.

Version 3 (April 19, 2019)

  1. Editorial change (moved change log to main article)

Version 2 (October 5, 2017)

  1. PR 84147 -  revised note on default special requirements

Version 1 (May 22, 2017)

  1. This is the converted Word File from from Chapter 70.
  2. PR 87714 - Realtime Duration and Handoff Window Duration can't be 0
  3. PR 87632 -  made order match the GUI