The Pioneer Anomaly

Abstract

Radio-metric Doppler tracking data received from the Pioneer 10 and 11 spacecraft from heliocentric distances of 20 -70 AU has consistently indicated the presence of a small, anomalous, blue-shifted frequency drift uniformly changing with a rate of ∼ 6 × 10 −9 Hz/s. Ultimately, the drift was interpreted as a constant sunward deceleration of each particular spacecraft at the level of aP = (8.74 ± 1.33) × 10 −10 m/s 2 . This apparent violation of the Newton's gravitational inverse-square law has become known as the Pioneer anomaly; the nature of this anomaly remains unexplained. In this review, we summarize the current knowledge of the physical properties of the anomaly and the conditions that led to its detection and characterization. We review various mechanisms proposed to explain the anomaly and discuss the current state of efforts to determine its nature. A comprehensive new investigation of the anomalous behavior of the two Pioneers has begun recently. The new efforts rely on the much-extended set of radio-metric Doppler data for both spacecraft in conjunction with the newly available complete record of their telemetry files and a large archive of original project documentation. As the new study is yet to report its findings, this review provides the necessary background for the new results to appear in the near future. In particular, we provide a significant amount of information on the design, operations and behavior of the two Pioneers during their entire missions, including descriptions of various data formats and techniques used for their navigation and radio-science data analysis. As most of this information was recovered relatively recently, it was not used in the previous studies of the Pioneer anomaly, but it is critical for the new investigation.

Support for temporally varying behavior of the Pioneer anomaly from the extended Pioneer 10 and 11 Doppler data sets

“…Following the 2002 study [3], an effort was initiated to collect all available Doppler data for both spacecraft [4,5]. Using standard data conditioning techniques [3], several decades-old archival data tracking files (see discussion in [5]) were converted to modern formats, processed, edited and filtered for corrupt data.…”

“…Uplink frequency records at NASA's Deep Space Network (DSN) were reconstructed from redundant information. We summarize the newly recovered Pioneer 10 & 11 Doppler data sets in Table I, including the range of dates covered and number of two-way and three-way [3,4] coherent Doppler data points available. The largest portion of the data lies in "deep space" ("DS") beyond planetary encounters (heliocentric distances of 18-80 AU and 9-32 AU for Pioneer 10 & 11 respectively).…”

“…As the Pioneers were spin-stabilized, periodic attitude maneuvers were required to realign the spin and antenna axis to the spacecraft-Earth direction to within 1.5 • . While attitude maneuvers used a fore-aft pair of thrusters in tandem, small residual impulses along the spin direction may occur for [4]. Information about maneuvers is available from recovered mission records and from the spacecraft telemetry [5], and is summarized in Table I.…”

“…There were also earlier reports that, in the case of Pioneer 11, the anomaly may have begun with a relatively sudden "onset" [3] shortly after the spacecraft's encounter with Saturn. This acceleration of unknown origin is today known as the Pioneer anomaly (for a review, see [4]). In this paper, we present an analysis of newly recovered Doppler data for both Pioneer 10 and 11, and probe the question of the constancy of the anomalous acceleration, as well as place constraints on its direction.…”

Is It Possible to Relate Mond With Hořava Gravity?

“…For example, it explains the rotation curves of different galaxies and the Tully-Fisher relation [2]. Besides, MOND has an explanation for the so called Pioneer anomaly [3]. We also have to mention that, MOND presents problems to predict the cluster's of galaxies dynamics, in this case however, the baryonic mass has not been measured with certainty [4].…”