AABEA Technical Seminar Series Date: July 16, 2023 Time: 12 PM Eastern Speaker: Dr. Nazma Ferdous, Principal Software Engineer Astronomical Planning and Support Space Telescope Science Institute (STScI)
ABSTRACT The James Webb Space Telescope (JWST) was launched on December 25th, 2021, and was placed into orbit around the second Sun-Earth Lagrange point on January 21st, 2022. After 6 months of commissioning JWST began its science operations on July 11th, 2022. The STScI developed the Spike planning and scheduling software in support of the Hubble Space Telescope as a general toolkit for planning and scheduling with the National Aeronautics and Space Administration (NASA). Although the SPIKE planning and scheduling software system was initially developed for the Hubble Space Telescope (HST), it was extended and specialized for JWST long range planning. This talk will present an overview of the observation planning and scheduling process flow for JWST showing how the core scheduling engine has been extended from the process used for HST. The new challenges faced and mitigated by the development team over the first 9 months of operations include: (1) Inadequacies and inflexibilities of quickly updating mission defined parameters that forces recalculation of observation constraints, had to be addressed. (2) Early in the mission the JWST mirror was unexpectedly hit by micro-meteoroids. JWST scheduling engine SPIKE needed to quickly introduce new constraints so that the primary mirror faces away from the trail of micro-meteoroids to minimize the future chance of meteoroid strikes. (3) A high percentage of JWST observations are linked to other observations via temporal (timing) constraints (e.g., Observation 2 after Observation 1 by 10-20 days). Unlike HST, the JWST observations sometimes are either executed outside of originally calculated windows or are skipped entirely which rendered the existing temporal constraint propagator that have been in place for over 30 years of HST operations, ineffective. The temporal constraint propagator had be extended to handle such anomalies. (4) A grating wheel for the JWST Mid Infrared instrument (MIRI) was found to have excess friction when switching directions during scheduling these observations. The team is currently developing software to mitigate the problems with the wheel by having the planning system define campaigns which control the frequency of direction changes and ensure that the wheel operates within safe limits.
