JWST Guiding on Moving Targets
Requirements and on flight performance of Moving Target tracking are discussed in this article.
See also: Moving Target Acquisition and Tracking
JWST was launched with a requirement to track objects at speeds up to 30 mas/s. During commissioning, tracking was demonstrated at rates up to 67 mas/sec.
All tests of moving targets were successful: centroids showed subpixel scatter in all instruments, jitter rms for the guider was typically <2mas (1-σ, radial), and image quality was comparable to that of fixed targets. Tracking at rates 30–70 mas/s had similar accuracy to that seen with lower rates. These tests verified science instrument performance for moving targets, including dithering and mosaicking.
During Cycle 1, tracking was successfully demonstrated at rates up to 110 mas, but with restrictions on exposure length.
Beginning with Cycle 2, tracking at rates up to 75 mas/s is supported by APT without special approval; shared-risk observations at rates 76–100 mas/s will be allowed, but only with careful coordination and approval from STScI moving target experts and operations support staff.