USING THE AUTO-ADJUST FEATURE FOR ORBIT PACKING

Overview

This document describes how to use the auto-adjust feature; see the training movie. The auto-adjust function can be used to pack your orbits in an automatic manner. For underfilled orbits, you select the sub-exposures whose Actual Durations (i.e. exposure times) you want to lengthen to use the remaining orbital visibility. Auto-adjust will divide the unused orbital visibility time equally amongst the sub-exposures you have selected to pack your orbits, leaving no more than 10s of unused visibility remaining. The auto-adjust function will work on both prime and parallel exposures.

Exclusions

While most classes of exposures are adjustable, certain classes are not (either with Auto-adjust or by manually setting the Actual Durations). Non-adjustable exposures include:

all WFC3/IR exposures
FGS TRANS mode exposures
all visits with LOW SKY, SHADOW, CVZ special requirements
all exposures with internal targets (such as WAVECALs)
there are other instrument-specific cases which will be noted later

Example 1 - WFC3

In Visit 01, we have a 600s (CR-SPLIT=2, 300s each sub-exposure) and a 1000s (CR-SPLIT=2, 500s each sub-exposure) exposure in Orbit 1, and a 4-point pattern (200s per exposure) in Orbit 2. An initial run of the

Orbit Planner reveals 222s of unused orbital visibility in Orbit 1, and 479s of unused orbital visibility in Orbit 2. We can either select all the sub-exposures or select a subset of sub-exposures to utilize the time. The

green box next to the exposure label in the

Orbit Planner display indicates the sub-exposure is adjustable.

To select all sub-exposures in the visit (if a multi-orbit visit, you can adjust all orbits at one time), you can either manually select each one or select no sub-exposures (which defaults to all sub-exposures). Note that if you select no sub-exposures, and some sub-exposures in the visit are not adjustable, Auto-adjust will only expand those sub-exposures that are adjustable. To select discrete sub-exposures, click on the sub-exposure in the Orbit Planner window or the Tree Editor. To select consecutive sub-exposures, click on the first sub-exposure, then Shift-click on the last sub-exposure desired. To select non-consecutive sub-exposures, click on the first sub-exposure, then Cntl-Click on the others.

In this example, we will select the last 2 sub-exposures in the Orbit 1, and the middle two pattern points in Orbit 2.

Clicking on the Auto-adjust button will initiate processing, and APT will divide the unused orbital visibility equally among each sub-exposure. Note that changing exposure times can result in changing overheads or buffer dumps, and APT will take these into account when packing your orbits. The results of Auto-adjust show that each sub-exposure in Orbit 1, which were originally 300s long, has now been expanded to 611s. In Orbit 2, the two middle pattern points, which were originally 200s long, have been expanded to 1087s; this leaves 41s of unused orbital visibility.

The reason there is so much unused orbital visibility (for Orbit 2) is due to buffer management.

Note that if you did not like the results, you can reset back to the original exposure times by hitting the Clear Actual Durations button. If, in addition, you wanted to also clear the orbit numbers, hit the Clear Orbit Numbers and Actual Durations button.

Example 2 - COS

In Visit 03, we have a target acquisition, followed by an 1800s G230L/2635 exposure in Orbit 1, a 1800s G230L/2950 exposure in Orbit 2, and a 1800s G230L/3000 exposure in Orbit 3. Note that the target acquisition exposure is not adjustable.

In this example, we will select no sub-exposures, which results in all adjustable sub-exposures being used.

After clicking on the Auto-adjust button, we see that all orbits are completely packed.

Last modified: May 21, 2014.