9 research outputs found
A Mission to Explore the Pioneer Anomaly
The Pioneer 10 and 11 spacecraft yielded the most precise navigation in deep
space to date. These spacecraft had exceptional acceleration sensitivity.
However, analysis of their radio-metric tracking data has consistently
indicated that at heliocentric distances of astronomical units,
the orbit determinations indicated the presence of a small, anomalous, Doppler
frequency drift. The drift is a blue-shift, uniformly changing with a rate of
Hz/s, which can be interpreted as a
constant sunward acceleration of each particular spacecraft of . This signal has become known as the Pioneer
anomaly. The inability to explain the anomalous behavior of the Pioneers with
conventional physics has contributed to growing discussion about its origin.
There is now an increasing number of proposals that attempt to explain the
anomaly outside conventional physics. This progress emphasizes the need for a
new experiment to explore the detected signal. Furthermore, the recent
extensive efforts led to the conclusion that only a dedicated experiment could
ultimately determine the nature of the found signal. We discuss the Pioneer
anomaly and present the next steps towards an understanding of its origin. We
specifically focus on the development of a mission to explore the Pioneer
Anomaly in a dedicated experiment conducted in deep space.Comment: 8 pages, 9 figures; invited talk given at the 2005 ESLAB Symposium
"Trends in Space Science and Cosmic Vision 2020", 19-21 April 2005, ESTEC,
Noordwijk, The Netherland
Fundamental Physics with the Laser Astrometric Test Of Relativity
The Laser Astrometric Test Of Relativity (LATOR) is a joint European-U.S.
Michelson-Morley-type experiment designed to test the pure tensor metric nature
of gravitation - a fundamental postulate of Einstein's theory of general
relativity. By using a combination of independent time-series of highly
accurate gravitational deflection of light in the immediate proximity to the
Sun, along with measurements of the Shapiro time delay on interplanetary scales
(to a precision respectively better than 0.1 picoradians and 1 cm), LATOR will
significantly improve our knowledge of relativistic gravity. The primary
mission objective is to i) measure the key post-Newtonian Eddington parameter
\gamma with accuracy of a part in 10^9. (1-\gamma) is a direct measure for
presence of a new interaction in gravitational theory, and, in its search,
LATOR goes a factor 30,000 beyond the present best result, Cassini's 2003 test.
The mission will also provide: ii) first measurement of gravity's non-linear
effects on light to ~0.01% accuracy; including both the Eddington \beta
parameter and also the spatial metric's 2nd order potential contribution (never
measured before); iii) direct measurement of the solar quadrupole moment J2
(currently unavailable) to accuracy of a part in 200 of its expected size; iv)
direct measurement of the "frame-dragging" effect on light by the Sun's
gravitomagnetic field, to 1% accuracy. LATOR's primary measurement pushes to
unprecedented accuracy the search for cosmologically relevant scalar-tensor
theories of gravity by looking for a remnant scalar field in today's solar
system. We discuss the mission design of this proposed experiment.Comment: 8 pages, 9 figures; invited talk given at the 2005 ESLAB Symposium
"Trends in Space Science and Cosmic Vision 2020," 19-21 April 2005, ESTEC,
Noodrwijk, The Netherland
Pioneer Anomaly and the Kuiper Belt mass distribution
Pioneer 10 and 11 were the first probes sent to study the outer planets of
the Solar System and Pioneer 10 was the first spacecraft to leave the Solar
System. Besides their already epic journeys, Pioneer 10 and 11 spacecraft were
subjected to an unaccounted effect interpreted as a constant acceleration
toward the Sun, the so-called Pioneer anomaly. One of the possibilities put
forward for explaining the Pioneer anomaly is the gravitational acceleration of
the Kuiper Belt. In this work we examine this hypothesis for various models for
the Kuiper Belt mass distribution. We find that the gravitational effect due to
the Kuiper Belt cannot account for the Pioneer anomaly. Furthermore, we have
also studied the hypothesis that drag forces can explain the the Pioneer
anomaly; however we conclude that the density required for producing the
Pioneer anomaly is many orders of magnitude greater than those of
interplanetary and interstellar dust. Our conclusions suggest that only through
a mission, the Pioneer anomaly can be confirmed and further investigated. If a
mission with these aims is ever sent to space, it turns out, on account of our
results, that it will be also a quite interesting probe to study the mass
distribution of the Kuiper Belt.Comment: Plain latex; 17 pages, 12 figures. Version to appear in Classical and
Quantum Gravity (2006
Quantum Physics Exploring Gravity in the Outer Solar System: The Sagas Project
We summarise the scientific and technological aspects of the SAGAS (Search
for Anomalous Gravitation using Atomic Sensors) project, submitted to ESA in
June 2007 in response to the Cosmic Vision 2015-2025 call for proposals. The
proposed mission aims at flying highly sensitive atomic sensors (optical clock,
cold atom accelerometer, optical link) on a Solar System escape trajectory in
the 2020 to 2030 time-frame. SAGAS has numerous science objectives in
fundamental physics and Solar System science, for example numerous tests of
general relativity and the exploration of the Kuiper belt. The combination of
highly sensitive atomic sensors and of the laser link well adapted for large
distances will allow measurements with unprecedented accuracy and on scales
never reached before. We present the proposed mission in some detail, with
particular emphasis on the science goals and associated measurements.Comment: 39 pages. Submitted in abridged version to Experimental Astronom