Non-standard Timing Models

JWST's Astronomer’s Proposal Tool (APT) estimates duration for each step in the proposal.This page describes non-standard cases where the standard timing models are not used.

Because of the nature of some templates which are handled almost exclusively within the Scripts, there are some cases where the standard timing model presented above is not used. Instead, there are a set of rules for calculating the timing for those templates. The following sections lists these non-standard timing models.

NIRISS focus

Calculate the timing as for a normal NIRISS visits, but note that there are additional exposures that will occur.

Table 1: NIRISS Focus Exposures

Delta Parameters

Number of Exposures

<blank>

12

1 position

2

N-positions, one containing 0.0

N+1

N-positions, not containing 0.0

N+2

NIRCam wheel exercise

If "ALL" is specified, all four wheels move simultaneously (almost). If individual wheels are specified, they are moved one at a time. One rotation is 360 degrees (or 12 spectral elements). The speed of the wheels in the current NIRCam FSW is approximately 1 element per second.

So the formula is NumWheels*NumRotations*12. Treat ALL as 1 Wheel.

NIRCam focus

Calculate the timing as for a normal NIRCam visits, but note that there are additional exposures that will occur. If there are N Linear Actuator positions, there will be N+1 exposures.

NIRCam IPR imaging

Use the following table to determine the number of exposures that will occur with this template. Each image takes 43 seconds.

Table 2: NIRCam IPR Imaging Number of Exposures

Module

PRIME

REDUNDANT

BOTH

ALL

15

15

24

A

9

9

15

ASHORT

6

6

12

ALONG

3

3

6

B

9

9

15

BSHORT

6

6

12

BLONG

3

3

6

MIRI anneal

MIRI Anneal duration is modeled as 500 seconds per detector for the entire anneal visit.

MIRI Anneal Duration = Anneal warmup OSS timeout + Anneal cooldown OSS timeout + MIRI anneal overhead

ActivityDuration in secondsPRD elementPRD file
Anneal warmup OSS timeout80 secondsmiri_anneal_warming_durationtiming_model_parameters
Anneal cooldown OSS timeout300 secondsmiri_anneal_cooling_durationtiming_model_parameters
Anneal overhead120 secondsmiri_anneal_overhead_durationtiming_model_parameters
Total500 seconds

FGS internal flat

FULLONLY will take about 700 s per pointing, WITHSUBARRAYS will take about 5500 s per pointing. Since 3 pointings are hardcoded into the OSS script, this will result in total times of about 2,100 and 16,500 seconds, respectively.

FGS focus

Fine guiding must be terminated prior to each move of the focus mechanism and reacquired after each move. This will require about 90 seconds per focus mechanism position. Unless only one position is supplied, there will be one additional position to return to the starting position.

NIRSpec focus

If there is one position and it is 0, then 1 exposures is taken.

If there is one position that is != 0, then 2 exposures are taken.

If there are N positions (N>1), then N+1 exposures are taken.

NIRSpec anneal

NIRSpec Anneal is modeled as taking 2765 seconds.

NIRSpec focus reference

We have no information for this template and are allocating 0 seconds.

NIRSpec MSA short detection

We have no information for this template and are allocating 0 seconds.

NIRSpec MSA masking

We have no information for this template and are allocating 0 seconds.

NIRSpec filter/grating wheel test

We have no information for this template and are allocating 0 seconds.

WFSC commissioning

There are a number of exposures taken equal to the Number of WFSC Groups + 1.

Realtime commanding

Science Duration is the value of the Realtime Duration field, while the instrument overhead is the sum of the Initial Setup Duration and Cleanup Duration fields. The Handoff Window Duration occurs in parallel with the other times and does not contribute to Science Duration. The maximum value allowed for this field is the sum of the values of the other three fields.

Science Duration = Realtime Duration

Instrument Overhead = Initial Setup Duration + Cleanup Duration

Station keeping

Science Duration is the value of the Realtime Duration field, while the instrument overhead is the sum of the Initial Setup Duration and Cleanup Duration fields. The Handoff Window Duration occurs in parallel with the other times and does not contribute to Science Duration. The maximum value allowed for this field is the sum of the values of the other three fields.

Science Duration = Realtime Duration

Instrument Overhead = Initial Setup Duration + Cleanup Duration

Safe mode recovery

Science Duration is the expected duration of the safe mode activity and is used for scheduling purposes.

Science Duration = Duration

Instrument Overhead = 20s Initial Setup from default OPE constraint overhead

Change log

 Click here to expand...

Version 3 (October 2, 2018)

  1. PR 90899 - updated durations in the MIRI Anneal section.


Version 2 (October 24, 2017)

  1. PR 88837 - added new sections for Realtime Commanding and Station Keeping.


Version 1 (June 6, 2017)

  1. Initial version.