978 research outputs found
Seeking a solution of the Pioneer Anomaly
The 1972 and 1973 launched Pioneer 10 and 11 were the first missions to
explore the outer solar system. They achieved stunning breakthroughs in
deep-space exploration. But around 1980 an unmodeled force of \sim 8 \times
10^{-8} cm/s^2, directed approximately towards the Sun, appeared in the
tracking data. It later was unambiguously verified as not being an artifact.
The origin remains unknown (although radiant heat remains a likely cause).
Increasing effort has gone into understanding this anomaly. We review the
situation and describe programs to resolve the issue.Comment: 7 pages, 1 figure, invited talk at the Fourth Meeting on CPT and
Lorentz Symmetry, 8-11 Aug. 2007, held at Indiana Universit
Earth Flyby Anomalies
In a reference frame fixed to the solar system's center of mass, a
satellite's energy will change as it is deflected by a planet. But a number of
satellites flying by Earth have also experienced energy changes in the
Earth-centered frame -- and that's a mystery.Comment: 5 pagea 3 figure
Lessons Learned from the Pioneers 10/11 for a Mission to Test the Pioneer Anomaly
Analysis of the radio-metric tracking data from the Pioneer 10/11 spacecraft
at distances between 20--70 astronomical units (AU) from the Sun has
consistently indicated the presence of an anomalous, small, constant Doppler
frequency drift. The drift is a blue-shift, uniformly changing with rate a_t =
(2.92 +/- 0.44) x 10^(-18) s/s^2. It can also be interpreted as a constant
acceleration of a_P = (8.74 +/- 1.33) x 10^(-8) cm/s^2 directed towards the
Sun. Although it is suspected that there is a systematic origin to the effect,
none has been found. As a result, the nature of this anomaly has become of
growing interest. Here we discuss the details of our recent investigation
focusing on the effects both external to and internal to the spacecraft, as
well as those due to modeling and computational techniques. We review some of
the mechanisms proposed to explain the anomaly and show their inability to
account for the observed behavior of the anomaly. We also present lessons
learned from this investigation for a potential deep-space experiment that will
reveal the origin of the discovered anomaly and also will characterize its
properties with an accuracy of at least two orders of magnitude below the
anomaly's size. A number of critical requirements and design considerations for
such a mission are outlined and addressed.Comment: 11 pages, invited talk given at ``35th COSPAR Scientific Assebly,''
July 18-24, 2004, Paris, Franc
Directly Measured Limit on the Interplanetary Matter Density from Pioneer 10 and 11
The Pioneer 10 and 11 spacecraft had exceptional deep-space navigational
capabilities. The accuracies of their orbit reconstruction were limited,
however, by a small, anomalous, Doppler frequency drift that can be interpreted
as an acceleration of (8.74 +/- 1.33) x 10^{-8} cm/s^2 directed toward the Sun.
We investigate the possibility that this anomaly could be due to a drag on the
spacecraft from their passing through the interplanetary medium. Although this
mechanism is an appealing one, the existing Pioneer radiometric data would
require an unexpectedly high mass density of interplanetary dust for this
mechanism to work. Further, the magnitude of the density would have to be
nearly constant at distances ~ 20-70 AU. Therefore, it appears that such an
explanation is very unlikely, if not ruled out. Despite this, the measured
frequency drift by itself places a directly-measured, model-independent limit
of \lessim 3 x 10^{-19} g/cm^3 on the mass density of interplanetary dust in
the outer(~20-70 AU) solar system. Lower experimental limits can be placed if
one presumes a model that varies with distance. An example is the limit \lessim
6 x 10^{-20} g/cm^3 obtained for the model with an axially-symmetric density
distribution that falls off as the inverse of the distance. We emphasize that
the limits obtained are experimentally-measured, in situ limits. A mission to
investigate the anomaly would be able to place a better limit on the density,
or perhaps even to measure it.Comment: 16 pages, 2 figures, publication versio
The Pioneer Anomaly: The Data, its Meaning, and a Future Test
The radio-metric Doppler tracking data from the Pioneer 10/11 spacecraft,
from between 20-70 AU, yields an unambiguous and independently confirmed
anomalous blue shift drift of a_t = (2.92 \pm 0.44)\times 10^{-18} s/s^2. It
can be interpreted as being due to a constant acceleration of a_P = (8.74 \pm
1.33) \times 10^{-8} cm/s^2 directed towards the Sun. No systematic effect has
been able to explain the anomaly, even though such an origin is an obvious
candidate. We discuss what has been learned (and what might still be learned)
from the data about the anomaly, its origin, and the mission design
characteristics that would be needed to test it. Future mission options are
proposed.Comment: 16 pages, 7 figures, to be published in the AIP Conference
Proceedings of the 2nd Mexican Meeting on Mathematical and Experimental
Physic
The Pioneer Anomaly and Its Implications
The Pioneer 10/11 spacecraft yielded the most precise navigation in deep
space to date. However, their radio-metric tracking data has consistently
indicated the presence of a small, anomalous, Doppler frequency drift. The
drift is a blue-shift, uniformly changing with a rate of ~6 x 10^{-9} Hz/s and
can be interpreted as a constant sunward acceleration of each particular
spacecraft of a_P =(8.74 +/- 1.33) x 10^{-10} m/s^2. The nature of this anomaly
remains unexplained. Here we summarize our current knowledge of the discovered
effect and review some of the mechanisms proposed for its explanation.
Currently we are preparing for the analysis of the entire set of the available
Pioneer 10/11 Doppler data which may shed a new light on the origin of the
anomaly. We present a preliminary assessment of such an intriguing possibility.Comment: 7 pages, 2 figures. Invited talk given at the XXIst IAP Colloquium on
"Mass Profiles and Shapes of Cosmological Structures", Paris, France, July
4-9, 200
The Energy Transfer Process in Planetary Flybys
We illustrate the energy transfer during planetary flybys as a function of
time using a number of flight mission examples. The energy transfer process is
rather more complicated than a monotonic increase (or decrease) of energy with
time. It exhibits temporary maxima and minima with time which then partially
moderate before the asymptotic condition is obtained. The energy transfer to
angular momentum is exhibited by an approximate Jacobi constant for the system.
We demonstrate this with flybys that have shown unexplained behaviors: i) the
possible onset of the "Pioneer anomaly" with the gravity assist of Pioneer 11
by Saturn to hyperbolic orbit (as well as the Pioneer 10 hyperbolic gravity
assist by Jupiter) and ii) the Earth flyby anomalies of small increases in
energy {\it in the geocentric system} (Galileo-I, NEAR, and Rosetta, in
additioon discussing the Cassini and Messenger flybys). Perhaps some small, as
yet unrecognized effect in the energy-transfer process can shed light on these
anomalies.Comment: 29 pages, 43 images combined into 13 figures. Additions to answer
comments of refere
Study of the Pioneer Anomaly: A Problem Set
Analysis of the radio-metric tracking data from the Pioneer 10 and 11
spacecraft at distances between 20--70 astronomical units from the Sun has
consistently indicated the presence of an anomalous, small, and constant
Doppler frequency drift. The drift is a blue-shift, uniformly changing at the
rate of (5.99 +/- 0.01) x 10^{-9} Hz/s. The signal also can be interpreted as a
constant acceleration of each particular spacecraft of (8.74 +/- 1.33) x
10^{-8} cm/s^2 directed toward the Sun. This interpretation has become known as
the Pioneer anomaly. We provide a problem set based on the detailed
investigation of this anomaly, the nature of which remains unexplained.Comment: 14 pages, 3 figures, 5 tables, minor corrections before publicatio
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