Commanding the James Webb Space Telescope using event-driven operations software

Abstract

This paper provides an overview of the event-driven architecture that will be used onboard the James Webb Space Telescope (JWST) to carry out the series of exposures, maneuvers, and engineering activities that were selected beforehand by the JWST planning and scheduling subsystem. Each week during one of the ground communication intervals one observation plan segment that contains an ordered list of tasks for JWST will be uploaded to the telescope. A set of JavaScripts running onboard JWST will be responsible for implementing the series of tasks listed in the weekly observation plan segments as sequences of flight software commands. The JavaScripts will execute the observation plan segments in an event-driven manner, in which the JavaScripts query JWST telemetry to determine when to execute the flight software commands needed to carry out the observation plan. The onboard JavaScripts consult command and telemetry dictionaries to construct command requests and CCSDS telemetry queries. This paper will demonstrate how creating flight software commands as they are needed onboard simplifies the ground to flight interface, and allows onboard events to be taken into consideration during operations.