The flyby anomaly is an unexpected energy increase during Earth-flybys In orbital mechanics and aerospace engineering, a gravitational slingshot, gravity assist maneuver or swing-by is the use of the relative movement and gravity of a planet or other celestial body to alter the path and speed of a spacecraft, typically in order to save propellant, time, and expense. Gravity assistance can be used to accelerate, of spacecraft. This anomaly has been observed as a shift in the S-Band The S band ranges from 2 to 4 GHz, crossing the conventional boundary between UHF and SHF at 3.0 GHz. It is part of the microwave band of the electromagnetic spectrum. The S band is used by weather radar, surface ship radar, and some communications satellites, especially those used by NASA to communicate with the Space Shuttle and the and X-Band The X-band is a segment of the microwave radio region of the electromagnetic spectrum. In some cases, such as in communication engineering, the frequency range of X-band is rather indefinitely set at approximately 7.0 to 11.2 gigahertz . In radar engineering, the frequency range is specified by the IEEE at 8.0 to 12.0 GHz Doppler The Doppler effect , named after Austrian physicist Christian Doppler who proposed it in 1842, is the change in frequency of a wave for an observer moving relative to the source of the wave. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from an observer. The received frequency is higher (compared to and the ranging data. Taken together it causes a significant unaccounted velocity increase of over 13 mm/s during flybys.^[1]

Observations

Gravitational assists In orbital mechanics and aerospace engineering, a gravitational slingshot, gravity assist maneuver or swing-by is the use of the relative movement and gravity of a planet or other celestial body to alter the path and speed of a spacecraft, typically in order to save propellant, time, and expense. Gravity assistance can be used to accelerate, are valuable techniques for solar system exploration. Because the success of these flyby maneuvers depends on the geometry of the trajectory A trajectory is the path a moving object follows through space as a function of time. The object might be a projectile or a satellite, for example. It thus includes the meaning of orbit—the path of a planet, an asteroid or a comet as it travels around a central mass. A trajectory can be described mathematically either by the geometry of the path,, the position and velocity of a spacecraft is continuously tracked during its encounter with a planet by the Deep Space Network The Deep Space Network, or DSN, is an international network of large antennas and communication facilities that supports interplanetary spacecraft missions, and radio and radar astronomy observations for the exploration of the solar system and the universe. The DSN should not be confused with the Interplanetary Transport Network. The network also (DSN).

The flyby anomaly was first noticed during a careful inspection of DSN Doppler data shortly after the Earth-flyby of the Galileo spacecraft Galileo was an unmanned spacecraft sent by NASA to study the planet Jupiter and its moons. Named after the astronomer and Renaissance pioneer Galileo Galilei, it was launched on October 18, 1989 by the Space Shuttle Atlantis on the STS-34 mission. It arrived at Jupiter on December 7, 1995, a little more than six years later, via gravitational on 8 December 1990. While the Doppler residuals (observed minus computed data) were expected to remain flat, the analysis revealed an unexpected 66 mHz shift, which corresponds to a velocity increase of 3.92 mm/s at perigee An apsis, plural apsides , is the point of greatest or least distance of a body from one of the foci of its elliptical orbit. In modern celestial mechanics this focus is also the center of attraction, which is usually the center of mass of the system. Historically, in geocentric systems, apsides were measured from the center of the Earth. An investigation of this effect at the Jet Propulsion Laboratory Jet Propulsion Laboratory is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. The facility is located in the City of La Canada Flintridge near the northern border of Pasadena. JPL is managed by the nearby California Institute of (JPL), the Goddard Space Flight Center The Goddard Space Flight Center is a major NASA space research laboratory established on May 1, 1959 as NASA's first space flight center. GSFC employs approximately 10,000 civil servants and contractors, and is located approximately 6.5 miles (10.5 km) northeast of Washington, D.C. in Greenbelt, Maryland, USA. GSFC, one of ten major NASA field (GSFC) and the University of Texas The University of Texas at Austin is a public research university located in Austin, Texas, United States, and is the flagship institution of The University of Texas System. The main campus is located approximately 0.25 miles (0.40 km) from the Texas State Capitol. Founded in 1883, the university has the fifth-largest single-campus enrollment in has not yielded a satisfactory explanation. It should be noted that no anomaly was detected after the second Earth-flyby of the Galileo spacecraft Galileo was an unmanned spacecraft sent by NASA to study the planet Jupiter and its moons. Named after the astronomer and Renaissance pioneer Galileo Galilei, it was launched on October 18, 1989 by the Space Shuttle Atlantis on the STS-34 mission. It arrived at Jupiter on December 7, 1995, a little more than six years later, via gravitational in December 1992, because any possible velocity increase was masked by atmospheric drag of the lower altitude of 303 km.

On 23 January 1998 the Near Earth Asteroid Rendezvous (NEAR The Near Earth Asteroid Rendezvous - Shoemaker , renamed after its 1996 launch in honor of planetary scientist Eugene M. Shoemaker, is a robotic space probe designed by NASA to study the near-Earth asteroid Eros from close orbit over a period of a year. The mission succeeded in closing in with the asteroid and orbited several times around it,) spacecraft experienced an anomalous velocity increase of 13.46 mm/s after its Earth encounter. Cassini-Huygens Cassini–Huygens is a joint NASA/ESA/ASI robotic spacecraft mission currently studying the planet Saturn and its many natural satellites. The spacecraft consists of two main elements: the NASA-designed and -constructed Cassini orbiter, named for the Italian-French astronomer Giovanni Domenico Cassini, and the ESA-developed Huygens probe, named gained ~0.11 mm/s in August 1999 and Rosetta Rosetta is a European Space Agency-led robotic spacecraft mission launched in 2004, intended to study the comet 67P/Churyumov-Gerasimenko. Rosetta consists of two main elements: the Rosetta space probe and the Philae lander. The spacecraft will also flyby and examine two asteroids on its way to the comet 1.82 mm/s after its Earth-flyby in March 2005.

An analysis of the MESSENGER spacecraft (studying Mercury Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about the axis for every two orbits. The perihelion of Mercury's orbit precesses around the) did not reveal any significant unexpected velocity increase. Scientists^[who?] think the reason for this may be that MESSENGER both approached and departed earth symmetrically about the equator (approached: latitude 31 degrees north The 31st parallel north is a circle of latitude that is 31 degrees north of the Earth's equatorial plane. It crosses Africa, Asia, the Pacific Ocean, North America and the Atlantic Ocean; departed: latitude 32 degrees south The 32nd parallel south is a circle of latitude that is 32 degrees south of the Earth's equatorial plane. It crosses the Atlantic Ocean, Africa, the Indian Ocean, Australasia, the Pacific Ocean and South America). This may suggest that the anomaly is related to Earth's rotation.

Summary of Earth-flyby spacecraft is provided in table below.^[2] It should be noted that the Rosetta data is for its first flyby in 2005; the second flyby produced no significant anomalous increase, and the third a negligible decrease.^[3]

Proposed equation

Empirical equation for flyby anomaly velocity change was proposed by J.D. Anderson et al.

where ω_e is the angular frequency In physics, angular frequency ω is a scalar measure of rotation rate. Angular frequency (or angular speed) is the magnitude of the vector quantity angular velocity. The term angular frequency vector is sometimes used as a synonym for the vector quantity angular velocity of Earth, R_e is the radius of Earth, and φ_i and φ_o are the inbound and outbound equatorial angles of the spacecraft.

In November 2009, ESA's Rosetta spacecraft Rosetta is a European Space Agency-led robotic spacecraft mission launched in 2004, intended to study the comet 67P/Churyumov-Gerasimenko. Rosetta consists of two main elements: the Rosetta space probe and the Philae lander. The spacecraft will also flyby and examine two asteroids on its way to the comet was tracked closely during flyby in order to precisely measure its velocity, in an effort to gather further data about the anomaly, but no significant anomaly was found.^[4]

Possible explanations

It is not known whether the flyby anomaly is related to the Pioneer anomaly The Pioneer anomaly or Pioneer effect is the observed deviation from predicted trajectories and velocities of various unmanned spacecraft visiting the outer solar system, most notably Pioneer 10 and Pioneer 11. In the case of spacecraft that transit over Earth's rotational or magnetic polar regions, the flyby anomaly is an acceleration rather than a deceleration. It is possible that during an equatorial transit an unmeasured small (relative to Earth) deceleration occurs; this is very similar to the Pioneer spacecraft's deceleration relative to the Sun.

Possible explanations of the flyby anomaly include:

• Unaccounted Transverse Doppler effect The relativistic Doppler effect is the change in frequency of light, caused by the relative motion of the source and the observer (as in the classical Doppler effect), when taking into account effects of the special theory of relativity, i.e. the redshift of light source with zero radial and non-zero tangential velocity^[5]. However, this cannot explain the similar anomaly in the ranging data, or the possibly related Pioneer anomaly The Pioneer anomaly or Pioneer effect is the observed deviation from predicted trajectories and velocities of various unmanned spacecraft visiting the outer solar system, most notably Pioneer 10 and Pioneer 11.
• A dark matter In astronomy and cosmology, dark matter is matter that is inferred to exist from gravitational effects on visible matter and background radiation, but is undetectable by emitted or scattered electromagnetic radiation. Its existence was hypothesized to account for discrepancies between measurements of the mass of galaxies, clusters of galaxies and halo around the Earth^[6].
• A Modification of Inertia resulting from a Hubble-scale Casimir effect (MIHsC). ^[7].
• The impact of General Relativity General relativity or the general theory of relativity is the geometric theory of gravitation published by Albert Einstein in 1915. It is the current description of gravitation in modern physics. It generalises special relativity and Newton's law of universal gravitation, providing a unified description of gravity as a geometric property of space, in its weak-field and linearized form yielding gravitoelectric and gravitomagnetic phenomena like, e.g., frame-dragging Albert Einstein's theory of general relativity predicts that rotating bodies drag spacetime around themselves in a phenomenon referred to as frame-dragging. The rotational frame-dragging effect was first derived from the theory of general relativity in 1918 by the Austrian physicists Josef Lense and Hans Thirring, and is also known as the Lense-, has been investigated as well^[8]: it turns out to be unable to account for the flyby anomaly.

References

1. ^ "ESA's Rosetta spacecraft may help unravel cosmic mystery". European Space Agency. November 12, 2009. http://www.spaceref.com/news/viewpr.html?pid=29609. Retrieved 13 March 2010.
2. ^ Anderson, John D.; James K. Campbell, Michael Martin Nieto (July 2007). "The energy transfer process in planetary flybys". New Astronomy 12 (5): 383–397. http://arxiv.org/abs/astro-ph/0608087.
3. ^ "Mystery remains: Rosetta fails to observe swingby anomaly". ESA. http://webservices.esa.int/blog/post/5/916.
4. ^ "ESA Spacecraft May Help Unravel Cosmic Mystery", ScienceDaily, Nov. 13, 2009, http://www.sciencedaily.com/releases/2009/11/091112103425.htm
5. ^ J. P. Mbelek (2008), Special relativity may account for the spacecraft flyby anomalies, arXiv The arXiv is an archive for electronic preprints of scientific papers in the fields of mathematics, physics, computer science, quantitative biology and statistics which can be accessed via the world wide web. In many fields of mathematics and physics, almost all scientific papers are placed on the arXiv. On 3 October 2008, arXiv.org passed the:0809.1888 [gr-qc]
6. ^ S.L.Adler (2008), Can the flyby anomaly be attributed to Earth-bound dark matter?, arXiv The arXiv is an archive for electronic preprints of scientific papers in the fields of mathematics, physics, computer science, quantitative biology and statistics which can be accessed via the world wide web. In many fields of mathematics and physics, almost all scientific papers are placed on the arXiv. On 3 October 2008, arXiv.org passed the:0805.2895 [astro-ph]
7. ^ M.E. McCulloch (2008), "Modelling the flyby anomalies using a modification of inertia", MNRAS-letters 389 (1): L57–L60, doi A digital object identifier is a character string used to uniquely identify an electronic document or other object. Metadata about the object is stored in association with the DOI name and this metadata may include a location, such as a URL, where the object can be found. The DOI for a document is permanent, whereas its location and other metadata:10.1111/j.1745-3933.2008.00523.x Preprint at arXiv The arXiv is an archive for electronic preprints of scientific papers in the fields of mathematics, physics, computer science, quantitative biology and statistics which can be accessed via the world wide web. In many fields of mathematics and physics, almost all scientific papers are placed on the arXiv. On 3 October 2008, arXiv.org passed the:0806.4159 [astro-ph].
8. ^ L. Iorio (2009), "The Effect of General Relativity on Hyperbolic Orbits and Its Application to the Flyby Anomaly", Scholarly Research Exchange 2009, doi A digital object identifier is a character string used to uniquely identify an electronic document or other object. Metadata about the object is stored in association with the DOI name and this metadata may include a location, such as a URL, where the object can be found. The DOI for a document is permanent, whereas its location and other metadata:10.3814/2009/807695, 807695

• P.G. Antreasian; J.R. Guinn (1998), "Investigations into the unexpected delta-v increase during the Earth Gravity Assist of GALILEO and NEAR", AIAA/AAS Astrodynamics Specialist Conf. and Exhibition, Boston, paper no. 98-4287, http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/20322/1/98-1237.pdf
• J.D. Anderson; J.G. Williams (2001), "Long-range tests of the equivalence principle", Class. Quantum Grav. Classical and Quantum Gravity is a peer-reviewed journal that covers all aspects of gravitational physics and the theory of spacetime 18 (13): 2447–2456, doi A digital object identifier is a character string used to uniquely identify an electronic document or other object. Metadata about the object is stored in association with the DOI name and this metadata may include a location, such as a URL, where the object can be found. The DOI for a document is permanent, whereas its location and other metadata:10.1088/0264-9381/18/13/307
• C. Lämmerzahl; O. Preuss; H. Dittus (2006), "Is the physics within the Solar system really understood?", Proceedings of the 359th WE-Heraeus Seminar on "Lasers, Clocks, and Drag-Free: Technologies for Future Exploration in Space and Tests of Gravity" , Preprint at arXiv The arXiv is an archive for electronic preprints of scientific papers in the fields of mathematics, physics, computer science, quantitative biology and statistics which can be accessed via the world wide web. In many fields of mathematics and physics, almost all scientific papers are placed on the arXiv. On 3 October 2008, arXiv.org passed the:gr-qc/0604052. Associated presentation slides
• J.D. Anderson; J.K. Campbell; M.M. Nieto (2006), The Energy Transfer Process in Planetary Flybys, arXiv The arXiv is an archive for electronic preprints of scientific papers in the fields of mathematics, physics, computer science, quantitative biology and statistics which can be accessed via the world wide web. In many fields of mathematics and physics, almost all scientific papers are placed on the arXiv. On 3 October 2008, arXiv.org passed the:astro-ph/0608087
• NASA Baffled by Unexplained Force Acting on Space Probes, at Space.com Space.com is a space and astronomy news website. Its stories are often syndicated to other media outlets, including CNN, MSNBC, Yahoo!, and USA Today
• J.D. Anderson; J.K. Campbell; J.E. Ekelund; J. Ellis; J.F. Jordan (2008), "Anomalous Orbital-Energy Changes Observed during Spacecraft Flybys of Earth", Phys. Rev. Lett. Physical Review Letters is one of the most prestigious journals in physics. Since 1958, it has been published by the American Physical Society as an outgrowth of Physical Review 100 (091102), doi A digital object identifier is a character string used to uniquely identify an electronic document or other object. Metadata about the object is stored in association with the DOI name and this metadata may include a location, such as a URL, where the object can be found. The DOI for a document is permanent, whereas its location and other metadata:10.1103/PhysRevLett.100.091102, http://www2.phys.canterbury.ac.nz/editorial/Anderson2008.pdf
• Wanted: Einstein Jr, at Economist.com
• K. Svozil (2008), Microphysical analogues of flyby anomalies, arXiv:0804.2198 [quant-ph]
• G. G. Nyambuya (2010), Are Flyby Anomalies and the Pioneer Effect an ASTG Phenomenon?, arXiv:0803.1370

External links

• Claus Lämmerzahl, University of Bremen:The Pioneer Anomaly or Do We Really Understand the Physics With the Solar System? (PDF file; 6.25 MB, 139 pages)
• Andreas Aste, University of Basel:Spacecraft Anomalies: An Update(PDF file; 9.8 MB, talk/slides)

Categories: Unsolved problems in physics | Gravitation

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