KEYWORDS: Mirrors, James Webb Space Telescope, Space telescopes, Space operations, Wavefront sensors, Observatories, Wavefronts, Interfaces, Point spread functions
Aligning and commissioning the James Webb Space Telescope's segmented mirrors after launch will last many months and involve the telescope itself, all science instruments, and all parts of the observatory ground system. In an effort to assess and demonstrate readiness of the complete end-to-end system - i.e. the flight optical telescope elements (OTE), the Integrated Science Instruments Module, the on-board operational scripts, and the ground processing infrastructure - we performed two operations tests during the JWST OTIS cryogenic campaign in 2017. They are the Wavefront Sensing and Control Demonstration activities at NASA Johnson Space Center (JSC), where we performed flight-like sensing and control using the flight software to command mirror moves and take measurements, and a "Shadow Mode test" at the Space Telescope Science Institute's Mission Operations Center (MOC), where we demonstrated processing of the JSC data through the entire ground system infrastructure. Overall, these tests demonstrated that the full system that will support OTE commissioning is soundly designed although still not fully mature. This paper focuses on the operations and systems testing aspects and some lessons learned. We also report on a series of Wavefront Rehearsals being held at the MOC that are providing additional opportunities to build team readiness in operating the ground system as a whole using high fidelity observatory simulators
In late 2015/early 2016, a major cryo-vacuum test was carried out for the Integrated Science Instrument Module (ISIM) of the James Webb Space Telescope (JWST). This test comprised the final cryo-certification and calibration test of the ISIM, after its ambient environmental test program (vibration, acoustics, EMI/EMC), and before its delivery for integration with the rest of the JWST observatory. Over the 108-day period of the round-the-clock test program, the full complement of ISIM flight instruments, structure, harness radiator, and electronics were put through a comprehensive program of thermal, optical, electrical, and operational tests. The test verified the health and excellent performance of the instruments and ISIM systems, proving the ISIM element’s readiness for integration with the telescope. We report here on the context, goals, setup, execution, and key results for this critical JWST milestone.
KEYWORDS: James Webb Space Telescope, Observatories, Calibration, Space operations, Mirrors, Computing systems, Stars, Space telescopes, Telescopes, Computer architecture
The software architecture of the James Webb Space Telescope (JWST) includes an operational layer implemented by
on-board JavaScripts that orchestrate event-driven operations. Request files specifying up to ten days of high-level
science and engineering tasks and a time-ordered execution list are uploaded periodically to the on-board event-driven
system. The processing of these files is dictated by on-board events. The tasks execute within their specified windows or
could be skipped due to an isolated anomaly, such as a guide star locate failure. For each high-level task, the necessary
flight software commands are constructed on-board according to operational rules, and positive completion confirmation
is required before proceeding to the next flight software command.
The event-driven nature of JWST operations presents challenges to the Science and Operations Center being constructed
at the Space Telescope Science Institute. This paper will outline the design implications on science and engineering
operations planning, flight real-time operations, and post-observation data management. Included will be descriptions of
how the Operations Center 1) plans time-windowed tasks to ensure that the event-driven system will remain
scientifically productive even when anomalies occur, 2) interfaces with and monitors JWST event-driven operations, and
3) records Observatory status information for each science image.
KEYWORDS: James Webb Space Telescope, Observatories, Software development, Mid-IR, Space telescopes, Stars, Space operations, Prototyping, Hubble Space Telescope, Commercial off the shelf technology
The James Webb Space Telescope (JWST) will use an event-driven system architecture to provide efficient and flexible operations as initiated by a simplified, high-level ground command interface. Event-driven operations is provided through the use of an on-board COTS JavaScript engine hosted within the payload flight software. After presenting the overall software architecture, we summarize the trade study that led to the selection of a commercial JavaScript interpreter and review our experiences developing scripts over the past year. Our script development approach is based upon the process successfully used at Space Telescope Science Institute for the last six Hubble Space Telescope science instruments. The major characteristics of our process are 1) coordinated development of the operational scripts and the flight software, 2) an incremental buildup of the operational requirements, and 3) recurring integrated testing. Our iterative script implementation process addresses how to gather requirements from a geographically dispersed team, and then how to design, build, and test the script software to accommodate the changes that are inevitable as flight hardware is built and tested. The concurrent development of the operational scripts and the flight software enables early and frequent "test-as-you-will-fly" verification, thus reducing the risk of on-orbit software problems.
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