In September 2006 a meter-sized object designated as 6R10DB9 was temporarily captured by Earth’s gravity and made three turns around Earth before leaving a geocentric orbit. This event provided an excellent case study for my upper-level undergraduate classical mechanics course. Students did a four-body (Sun, Earth, Moon, and 6R10DB9) simulation to reproduce the object’s path and examine its dynamics. The initial positions and velocities were downloaded from the Jet Propulsion Laboratory Horizons service. It was found that the Moon’s presence causes 6R10DB9 to orbit Earth three times rather than once. Coupling multi-body dynamical models with Horizons data allows numerous other potential applications for physics and astronomy classes and student research projects; several possibilities are suggested.

Topics
Classical mechanics, Atmospheric radiation, Ephemerides, Asteroids, Solar system dwarf planets, Gravitational force, Numerical integration, Complex systems theory, Educational assessment
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See EPAPS Document No. E-AJPIAS-76-017805 for the MATHCAD software and sample Horizons data to reproduce the four-body solution for 6R10DB9, Sun, Earth, and Moon. For more information on EPAPS, see http://www.aip.org/pubservs/epaps.html.
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6R10DB9 can be found by searching for “NEOCP 6R10DB9” or by choosing the “spacecraft” option and scrolling down the list to find the object.
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The vector data in the Horizons output file contain alternating lines of date/time, position, and velocity. To facilitate reading into MATHCAD these data were separated into two files, one for position (three columns for x⁠, y⁠, and z components of the position) and one for velocity (three columns for x⁠, y⁠, and z components of the velocity).
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© 2008 American Association of Physics Teachers.
2008
American Association of Physics Teachers

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