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Development of Satellite and Hazard Detection and Tracking
Capability for Spacecraft Flybys, 15-9097

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Principal Investigators
William J. Merline
William B. Colwell
Clark R. Chapman

Inclusive Dates: 09/16/98 - 01/16/99

Background - Detection of debris and orbiting bodies around spacecraft targets is important for several reasons. Flyby and orbital-encounter missions are subject to hazards posed by orbiting debris and unknown satellites that could result in loss of spacecraft or mission objectives through collisions and gravitational perturbation. Flyby missions, which occur over tens of minutes and on a timescale comparable to the round-trip light-time, have insufficient time to send data to the ground for analysis and to uplink new instructions to the spacecraft. Overall science return from a flyby mission would be significantly enhanced by automated real-time target identification capability based directly on data from the spacecraft's "eyes," thus closing the loop by autonomous on-board decision-making and enabling acquisition of higher quality data. Current spacecraft do not have this capability.

Approach - The objective of this project was to complete development of SwRI’s satellite/hazard detection software to take advantage of the December 1998 -January 1999 encounter of the Near Earth Asteroid Rendezvous (NEAR) spacecraft with the asteroid Eros. This unique and timely opportunity allowed SwRI to apply the software in a real-time situation with actual spacecraft data as it arrived on the ground. The simulation consisted of obtaining image files as they were downlinked from the NEAR spacecraft, identifying known and potential objects within each image, and then processing sequences of images to remove cosmic ray noise and identify persistent unknown objects -- candidates for asteroid satellites. However, on December 20, 1998, the orbital insertion engine on NEAR shut down prematurely, causing NEAR to approach Eros at 3,600 kilometers per hour rather than the planned 32 kilometers per hour. This premature shutdown changed the mission from an orbital insertion to a fast flyby and moved the arrival date from January 10 to December 23, just three days away. This situation presented the research team with a real challenge in that the planned activities were changed from one of analyzing a series of observations taken on a slow approach covering three weeks to a fast flyby contingency scenario with less than three days to prepare. The team redesigned the software and search strategies to accommodate this change and applied the semiautonomous software to the data in parallel with human data analysis.

Accomplishments - The SwRI software development and demonstration were successful, under even the unexpectedly severe and demanding conditions. Rapid analysis of the satellite data enabled the results to be reported within two weeks of the flyby, a much more rapid time frame than was possible for the entirely human analysis of the August 1997 NEAR flyby of asteroid Mathilde. No satellite was discovered by either the automated or traditional human-search methods, and these results have been presented at a conference. However, the recent ground-based discovery of the second ever-identified asteroid satellite by one of the principal investigators reinforces the need for this technology on future flyby missions. The software performed well, the objectives were met, and SwRI is in a much stronger position to approach future missions or projects with its satellite-detection technology. SwRI is currently applying this technology to search for vulcanoids, that is, asteroids that orbit the sun within the orbit of Mercury. The Institute will apply the knowledge gained from this effort to the next NEAR/Eros encounter in February 2000. The success of this project has opened opportunities for funding on pending missions and ensured external funding from the Jet Propulsion Laboratory for scientific support of on-board science analysis for at least one year and possibly well beyond. This work has supported the Institute’s developing expertise in automated analysis, which has been influential in identification of the NASA Applied Information Systems Research program as a new source of external funding.

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