SPHERES ISS Test Sessions

Test Session Details

NameSlosh, Formation Flight, and Lost in Space Maneuvers
GMT Date339/2009
Start (ET)09:10
End (ET)19:12
Crew MembersJeff Williams

The SPHERES Test Session 20 occurred on 2009-December-05, operated by astronaut Jeffrey Williams. Overall, the session went smoothly with operational difficulties quickly resolved. A total of 28 tests were run in 2.5 hours. These tests were organized into three groups that tested the following research areas: (1) fluid slosh, (2) formation flight and human supervision, and (3) lost in space maneuvers.

The fluid slosh tests investigated four linear translations to check for experiment repeatability, thruster characterization, and spin stabilization. The tests conducted built upon present data and allowed for identification of the apparent slosh event observed in Test Session 18. It was determined that acceleration levels induced by the satellite in its current configuration are too low to induce a slosh event that adversely affects the satellite’s trajectory.

The first formation flight test that was run explored using a relative controller that accounted for the coupled dynamics of the satellites, while not controlling the centroid of the formation in order to reduce fuel usage. The test was successful in reducing fuel usage while maintaining precision in relative positioning. Another formation flight test investigated using a diamond-shaped path as an alternative to an interferometric spiral to reduce test time. The test was successful in reducing the time of the test, but fuel usage increased and precision decreased. Additionally, new control laws for formation flight that use only relative information to converge to a circular formation were tested. These control laws validated previous analytical results and could be helpful for deep space formation missions. The tests successfully achieved control in the formation plane. Tests on human supervision were run to test collision avoidance techniques with different levels of crew involvement. The autonomous collision avoidance algorithm allowed the crew to focus on the actual task rather than avoiding collisions. That way, the human task performance could be enhanced. The repositioning task of a satellite was performed in a shorter amount of time with less fuel. No collisions occured during the tests and the autonomous collision avoidance algorithm was proven to work reliably when used in scenarios with human interaction. Further, the test on human navigation showed that the crew can approach multiple targets in three-dimensional space with high accuracy and safety.

Finally, several formation acquisition tests were run. They successfully used relative measurements to create a formation with limited knowledge of the other members of the formation using a limited field-of-view instrument.

Test PlanOnline test plan: View
Results ReportSPHERES_ISS_TS020_Report.pdf
Last Updated byedlopez
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Source last updated: 2014/07/24 15:13:38 by alvarso