Fly-by anomaly

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The fly-by anomaly describes a previously unexplained phenomenon in gravitational research . This is a small additional increase in speed that several space probes experienced during a fly-by on Earth.

observation

So-called fly-by maneuvers are often carried out after space probes have been launched. During these maneuvers, the probes sometimes fly past the earth several times and the path of the missions before and after a fly-by is recorded with high precision. Deviations from the predicted speed were measured for the first time in 1990 on the Galileo space probe .

During the first flyby of the Galileo spacecraft on December 8, 1990 at an altitude of 959.9 kilometers, an increase in the Doppler shift of the 5 GHz signal sent by Galileo by 66 mHz was found, which corresponded to an unexpected increase in speed of 3.92 mm / s. Extensive tests at the Jet Propulsion Laboratory , Goddard Space Flight Center and the University of Texas could not find any measurement errors or other explanations for the deviations. When Galileo approached Earth to within 303.1 kilometers during the second Earth flyby on December 8, 1992, the probe was already flying through the high atmosphere . Suitable measurements to confirm the discrepancies discovered on the first flyby were therefore not possible.

Further deviations were subsequently also observed in the NEAR Shoemaker and Rosetta space probes . When the NEAR Shoemaker probe passed Earth at a distance of 538.8 kilometers on January 23, 1998, there was an unexpected increase in the Doppler shift of 730 mHz, which corresponds to a speed increase of 13.46 mm / s. This was the largest deviation observed to date. When the Rosetta space probe flew past Earth at an altitude of 1954 kilometers on March 4, 2005, the Doppler measurements revealed an inexplicable increase in speed of 1.82 mm / s. The data from the Cassini-Huygens space probe cannot be used in this regard, as the probe accelerated via its own engines during the fly-by. In contrast, no fly-by anomaly was measured in the Messenger space probe in August 2005.

Changes in airspeed have also been observed in the Pioneer 10 and 11 space probes since the 1980s . There the phenomenon is referred to as the Pioneer anomaly . It has been speculated that it is the same phenomenon. Meanwhile, however, the puzzle of the Pioneer anomaly seems solved, which means that the fly-by anomaly should have another cause.

Attempts to explain

The currently inexplicable discrepancy is small enough to be neglected in satellite missions, but leads to doubts as to whether the gravitational physics of the solar system is fully understood. The Lense-Thirring effect predicted by general relativity is insufficient for the observations. In the meantime, researchers at the Jet Propulsion Laboratory have developed an empirical formula for calculating the fly-by anomaly, according to which it depends on the approach and take-off angles in relation to the equator. During the flyby of the Rosetta space probe in November 2007, however, a deviation determined on the basis of this formula could not be confirmed.

A hypothesis by Jean-Paul Mbelek from the French nuclear research center CEA-Saclay proposes to explain the anomaly with the special theory of relativity . In his opinion, the anomaly is not a physical effect in the true sense of the word, but is only due to the inadequate, because non-relativistic, consideration of the phenomenon.

Since the fly-by anomaly did not occur on the second and third fly-bys of the Rosetta space probe , researchers from the International Flyby Collaboration at the International Space Science Institute (ISSI), Bern, who are researching the fly-by anomaly, are now also stopping an inaccuracy in the algorithm from the 1960s, which all computer programs use to calculate fly-bys, is conceivable.

See also

literature

  • Oliver Preuss, Hansjörg Dittus and Claus Lämmerzahl: surprises on the doorstep . In: Stars and Space . tape 46 , no. 4 , April 2007, ISSN  0039-1263 , p. 26-36 .
  • RA Lewis: Field Theory Model of the Flyby Anomaly . In: AIP Conf. Proc. tape 1103 , March 23, 2009, p. 226-234 , doi : 10.1063 / 1.3115499 .

Web links

Individual evidence

  1. ↑ a b picture of science: puzzling speed boost. March 1, 2008, accessed September 8, 2019 .
  2. ↑ a b Researchers Investigate New Cosmic Mystery: The Flyby Anomaly ( Memento of November 10, 2009 in the Internet Archive )
  3. ↑ Guido Meyer: Mysterious force throws space probes off track , Spiegel Online, March 12, 2008.
  4. ↑ Ute Kehse: Pioneer anomaly solved, Rosetta puzzle remains exciting . In: Wissenschaft.de. May 31, 2011, accessed September 8, 2019 .
  5. ↑ NZZ.ch: Strange accelerations in the solar system: The orbital deviations of some space probes in the earth's gravitational field pose a difficult puzzle for physicists
  6. ↑ Einstein's theory could explain fly-by anomaly
  7. ↑ direct spectrum: anomalous anomaly by Maike Pollmann