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Flyby Anomaly  
Information about the Pioneer Anomaly and anomalous velocity increases during Earth flyby's.
Chris P. Duif

Pioneer 10
  Rosetta's Earth flyby

Space probes have exhibited unexplained changes in speed during so-called Earth gravity assists (see links on the left). When NASA's Galileo and NEAR spacecraft and ESA's Rosetta flew past Earth, they showed an expected change in speed. The largest anomaly was recorded for NEAR, whose velocity changed 13 millimetres per second more than it should have. This excess is much larger than the expected errors in measurement.

ESA Blog: Mystery remains: Rosetta fails to observe swingby anomaly

  • P.G. Antreasian and J.R. Guinn, Investigations into the unexpected delta-V increases during the Earth gravity assists of Galileo and NEAR, AIAA 98-4287 (available at this site, pdf, 1.4 MB).
  • Abstract: Unexpected energy increases during Earth flybys of both the Galileo and Near Earth Asteroid Rendezvous (NEAR) spacecraft have drawn evidence of spacecraft trajectory modeling errors, an unknown perturbing force or failure of Newtonian gravity. This paper investigates the gravity field of Earth as a possible source of these anomalous Delta-Vs. Other possible sources of errors are considered, including: the mathematical models representing the perturbing forces acting on the spacecraft while in the sphere of influence of Earth, such as relativistic effects, tidal effects, Earth radiation pressure, and atmospheric drag. However, most of these perturbations, such as atmospheric drag, can be ruled out because the acceleration imparted to the spacecraft is several orders of magnitude less than observed. Since the oblateness effect is several orders of magnitude greater than the non-gravitational perturbations, errors in the spherical harmonic representation of Earth''s gravity field are examined. Other sources that have already been examined and tentatively dismissed include numerical round-off, integration errors, spacecraft antenna phase center offset, and spacecraft antenna switching during encounter.

  • J.D. Anderson and J.G. Williams, Long range tests of the equivalence principle, Class. Quant. Grav. 18 (2001) 2447.

  • Is the physics within the Solar system really understood? C. Lämmerzahl, O. Preuss, H. Dittus. gr-qc/0604052.
  • J.D. Anderson, J.K. Campbell, M.M. Nieto, The Energy Transfer Process in Planetary Flybys, astro-ph/0608087.

  • L. Iorio, The effect of general relativity on hyperbolic orbits and its application to the flyby anomaly, gr-qc/0811.3924.

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