James Webb Space Telescope Ground to Flight Interface Design

The James Webb Space Telescope (JWST) is a space-based infrared observatory planned for launch in 2013, which leverages the Hubble Space Telescope (HST) technical and scientific expertise. Unlike HST, JWST uses an event-driven design for 7 to 10 days of autonomous spacecraft and science operations. In the JWST event-driven commanding design, scripts onboard the observatory construct and issue commands in real-time to the flight-software. The on-board scripts interrogate telemetry to determine whether the issued command has been completed. Event-driven commanding simplifies the software systems, especially the uplink products needed for the spacecraft and science operations, since most of the command creation occurs on-board the spacecraft. The JWST high-level ground to flight interface consists of the uplink products and the on-board script directives used to drive science operations. The purpose of the uplink products is to tell the telescope where to look and to specify the observation and instrument parameters. The on-board script directives allow re-planning of observations from the ground in real-time without interrupting ongoing observatory operations. This paper describes the ground to flight interface design and its advantages, which include commonality, simplicity and low lifecycle costs.