Event-driven James Webb Space Telescope operations using on-board JavaScripts - art. no. 62740A

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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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... In the absolute time commanding design, similar events will consume valuable telescope time, since the onboard software will wait until the affected observation time has elapsed before proceeding to the next observation. For further discussion regarding the JWST event-driven commanding concept and operations, see Balzano and Isaacs (2006). ...
... The process for the on-board script development applies a " test-as-you-will-fly " philosophy (Balzano & Isaacs, 2006). The " test-as-you-will-fly " approach involves early and frequent testing of the on-board scripts, which includes realistic flight scenarios and failure cases. ...
... Based on the Visit parameters, the on-board scripts will generate the associated commands in real-time, which are issued to the flight software for execution. (Balzano and Zak, 2006) In the Visit file (refer to Figure 4), observation parameters are specified in a layered fashion: ...
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.
The James Webb Space Telescope (JWST) will enable a wealth of new scientific investigations in the near- and mid-infrared, with sensitivity and spatial/spectral resolution greatly surpassing its predecessors. In this paper, we focus upon Solar System science facilitated by JWST, discussing the most current information available concerning JWST instrument properties and observing techniques relevant to planetary science. We also present numerous example observing scenarios for a wide variety of Solar System targets to illustrate the potential of JWST science to the Solar System community. This paper updates and supersedes the Solar System white paper published by the JWST Project in 2010. It is based both on that paper and on a workshop held at the annual meeting of the Division for Planetary Sciences in Reno, NV, in 2012.
In this paper, the authors propose a concept of an onboard management mechanism to handle mission planning, scheduling, executing, and system monitoring, that is commonly necessary for many fields of autonomous remote systems. The main emphasis is placed on the onboard script-engine to implement the algorithm of re-planning of on-going mission so that the paper introduces a new type of command, “logic command”. The logic command is a kind of a sub-routine that can be sent in the same way as usual commands, but it makes onboard software behavior change to respond in any situation. In addition, an experimental implementation of the proposal onto an AUV is also shown.
The observer program implementation, planning, and scheduling subsystems are undergoing software development for the James Webb Space Telescope front-end ground segment and are being tested in an integrated fashion. This part of the ground system leverages what was developed and fine-tuned for the Hubble Space Telescope over previous decades. This paper will describe the testing design, methods, results, plus the current capabilities and elements still to be developed for these subsystems through the time of publication. We will point out elements from Hubble's systems, from an operations perspective, which have been preserved for the new telescope, and those which require redevelopment.
The James Webb Space Telescope (JWST) will be a powerful space observatory whose four science instruments will deliver rich imaging and multiplexed spectroscopic datasets to the astronomical and planetary science communities. The ground segment for JWST, now being designed and built, will carry out JWST's science operations. The ground segment includes: software that the scientific community will use to propose and specify new observations; systems that will schedule science and calibration observations in a way that respects physical and investigator-specified constraints, while satisfying preferences for efficient observing, low background levels, and distributed subscription across a year; the infrastructure to regularly measure and maintain the telescope's wavefront; orbit determination, ranging, and tracking; communication via the Deep Space Network to command the observatory and retrieve scientific data; onboard scripts that execute each observing program in an event-driven fashion, with occasional interruptions for targets of opportunity or time-critical observations; and a system that processes and calibrates the data into science-ready products, automatically recalibrates when calibrations improve, and archives the data for timely access by the principal investigator and later worldwide access by the scientific community. This ground system builds on experience from operating the Hubble Space Telescope, while solving challenges that are unique to JWST. In this paper, we describe the elements of the JWST ground system, how it will work operationally from the perspective of the observatory itself, and how a typical user will interact with the system to turn their idea into scientific discovery.
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.
At the Space Telescope Science Institute, the Data Management Subsystem (DMS) is responsible for data reformatting from telemetry to FITS, pipeline calibration, and providing the data archive. A DMS has been previously developed for two astronomical telescopes in space, the Hubble Space Telescope and the Kepler Mission. DMS software analysis and design has begun for the James Webb Space Telescope (JWST), which is scheduled for launch in 2014 by the National Aeronautics and Space Administration. Although there will be a great deal of software reuse from the previous missions, differences in the operations concept for JWST will have implications for the DMS software system architecture. A number of the design challenges for the DMS software system architecture that result from the JWST operations concept will be considered. Event-driven operations, which mean the detailed observation schedule cannot be predicted ahead of execution time, will require extensive changes to the data flow at the beginning of DMS science data processing. A scheme for priority processing of exposures must be implemented to insure rapid turn-around on time critical wave front sensing data. JWST science data product design will reflect infrared detectors utilizing up-the-ramp processing. The concept of an observation in program planning will result in a new model to associate exposures and form higher level data products. In addition, the JWST DMS will introduce a new paradigm for reprocessing to meet data user demands and be compatible with the Virtual Observatory protocols.
In this paper we propose an onboard software framework for many types of remote systems with the capabilit y of dynamic self-update without halting the software or shutting the hardware system, which are necessary for conventional onboard software updates. The key idea is to express an operational plan, which is usually a sequence of system-built-in commands, as a text script. This script contains not only the conventional plan but also "logic"-type commands so that the operational plan can be expressed in the form of a program fragment such as "IF A THEN DO B". Once this logic-type command is received, a remote system can change its behavior without requiring the software to be rebooted. Using this software architecture, we propose a new search algorithm using an orthogonal experiment design in the onboard planning and scheduling process; orthogonal experiment designs have been used in many quality control processes. Heuristics is used in conventional applications to create options for what to do next in the planning process, whereas here the focus is placed on transforming the conventional use of the orthogonal experiment design to create sufficient number of optional plans for the system to test as small as possible. Finally, we report the result of a demonstration experiment using an autonomous underwater vehicle that is controlled by onboard software based on the proposed software architecture and the searching algorithm.
The James Webb Space Telescope (JWST) will use an innovative event-driven architecture, which will maximize the flexibility of telescope operations. The autonomy of the event-driven system provides commanding of the spacecraft and science instruments based on the telemetry response. In the event of a failure, the telescope will continue with the portions of the science observation plan unaffected by the event, maximizing the efficiency of the observatory. Furthermore, lessons learned from the successful Hubble Space Telescope (HST) mission result in several lifecycle reduction measures, including a high-level ground to flight interface to minimize ground systems, since the detailed planning traditionally performed by ground software systems will be accomplished on-board the spacecraft. After reviewing the HST and JWST space telescope operations, the JWST event-driven design will be discussed and how it minimizes ground systems. Also, other cost-effective approaches employed by JWST will be presented. 1. BACKGROUND
Conference Paper
In this paper we propose an algorithm of onboard mission replanning using the orthogonal array to solve the problem of repairing of the original mission plan without human operator interventions. The orthogonal array plays an important role to create a group of tentative plans more efficiently than heuristics that is commonly used in standard onboard planning applications. The key idea to implement the proposing mission replanning software is the expression of an operational plan by a “script”. Most spacecraft mission plans are defined as a sequence of system-built-in commands, whereas this “script” contains not only the usual plans but also “logic” type commands. The logic type command is expressed in a form of a program fragment such as “IF A THEN DO B”. To make a further discussion on the proposing idea, this paper also shows a result of an experiment using an autonomous underwater vehicle. The onboard software is based on the proposing software architecture and the replanning algorithm to demonstrate its feasibility in an actual circumstance.
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