JWST's Astronomer’s Proposal Tool (APT) estimates duration for each step in the proposal. This page provides reference tables used in estimation, including slew times, guide star breaking distance, and dither overhead duration

Slew reference tables

   see JWST Slew Times and Overheads

• Duration of Initial slew is 2100 seconds for each new observation, or first visit of a multiple-visit observation (from PRD spacecraft_parameters).
• For subsequent slews, overhead is the slew duration based on distance as as shown in Table 2, plus any guide star dither overhead as shown in Table 1. 

Tables include:

APT guide star dither overhead table

There is an additional overhead for the Guide Star Reacquisition based on the amount of movement in a Slew or SAM, when guiding on FINE, MOVING, or TRACK Modes. Overheads durations are shown in Table 1. 

Table 1.  APT guide star dither overhead

Source: PRDAPTSOC-054, GS_dither_overhead

APT visit slew table

This table applies to all telescope moves modeled by APT, including slews between visits, as well as inside them. Distances between values are interpolated. Note that the distance you can slew within a visit is based on the Galactic latitude of the target, as shown in the Guide Star Breaking Distance table.

Table 2. APT visit slew duration

Source: PRDAPTSOC-058-002, visit_slew

Guide star breaking distance table

Table 3. Guide star breaking distance

Source: PRDAPTSOC-054, visit_splitting_table

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