In summary a 140 meter diameter equivalent, Hayabusa-shaped NEO, with a rotation period
of 6 hours was approached by the t-GT spacecraft with the initial task of determining a
precise orbit for the NEO. Effective convergence in the orbit determination was reached
after approximately 8 days of tracking and resulted in about a 5 meter (one sigma) error
ellipse projected forward 18 years in time. A second orbit determination was performed
following a simulated kinetic impact deflection during which the t-GT functioned as a standoff
observer. The post-deflection orbit determination converged to the pre-deflection
precision level of accuracy in only one day of tracking.
The solar powered, 1150kg. t-GT spacecraft towing performance evaluation was performed
in a 200 day simulated operation in which the t-GT was stationed 155 meters forward of the
NEO center of mass along its velocity vector. A very simple control law was employed to
maintain the spacecraft within a “box” centered on this nominal location. No control
problems or unusual excursions were experienced during the months of towing which
produced the desired velocity change of ~0.07cm/sec. During towing a NEO acceleration of
0.22 microns/sec/day was achieved at a fuel expenditure of approximately 0.05 kg/day.
EDIT:
oops, they fail:
Our preferred solution to deflecting an incoming near Earth asteroid (NEA), for reasons that are clarified below, is to rendezvous and "dock" with it at either its North or South Pole, realign the asteroid’s spin vector to a preferred direction and then push it (gently and for a long time) until we’ve changed its speed enough to miss the Earth. This scenario is very direct. It makes the key assumption, well supported by statistics and common sense that we will know of a pending impact many years ahead of time. The strange logic of NEA detection is that we will either know that an impact is pending several decades ahead of time, or that we will be hit by an asteroid we don’t know about with no warning at all! The critical importance of the detection program is that as you detect and track more and more NEAs you increase the former category and reduce the latter.
of 6 hours was approached by the t-GT spacecraft with the initial task of determining a
precise orbit for the NEO. Effective convergence in the orbit determination was reached
after approximately 8 days of tracking and resulted in about a 5 meter (one sigma) error
ellipse projected forward 18 years in time. A second orbit determination was performed
following a simulated kinetic impact deflection during which the t-GT functioned as a standoff
observer. The post-deflection orbit determination converged to the pre-deflection
precision level of accuracy in only one day of tracking.
The solar powered, 1150kg. t-GT spacecraft towing performance evaluation was performed
in a 200 day simulated operation in which the t-GT was stationed 155 meters forward of the
NEO center of mass along its velocity vector. A very simple control law was employed to
maintain the spacecraft within a “box” centered on this nominal location. No control
problems or unusual excursions were experienced during the months of towing which
produced the desired velocity change of ~0.07cm/sec. During towing a NEO acceleration of
0.22 microns/sec/day was achieved at a fuel expenditure of approximately 0.05 kg/day.
EDIT:
oops, they fail:
Our preferred solution to deflecting an incoming near Earth asteroid (NEA), for reasons that are clarified below, is to rendezvous and "dock" with it at either its North or South Pole, realign the asteroid’s spin vector to a preferred direction and then push it (gently and for a long time) until we’ve changed its speed enough to miss the Earth. This scenario is very direct. It makes the key assumption, well supported by statistics and common sense that we will know of a pending impact many years ahead of time. The strange logic of NEA detection is that we will either know that an impact is pending several decades ahead of time, or that we will be hit by an asteroid we don’t know about with no warning at all! The critical importance of the detection program is that as you detect and track more and more NEAs you increase the former category and reduce the latter.