A5039807256- Astro and Planetary Science
- Geophysics and Gravity Measurements
- Cosmology and Gravitation Theories
- Stellar, planetary, and galactic studies
- Planetary Science and Exploration
- Solar and Space Plasma Dynamics
- Adaptive optics and wavefront sensing
- Pulsars and Gravitational Waves Research
- Relativity and Gravitational Theory
- Astronomy and Astrophysical Research
- History and Developments in Astronomy
- Space Science and Extraterrestrial Life
- Dark Matter and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Gamma-ray bursts and supernovae
- Scientific Research and Discoveries
- Spacecraft Dynamics and Control
- Spacecraft and Cryogenic Technologies
- Black Holes and Theoretical Physics
- Astrophysics and Cosmic Phenomena
- Calibration and Measurement Techniques
- Advanced Frequency and Time Standards
- Space Satellite Systems and Control
- Astronomical Observations and Instrumentation
- Spacecraft Design and Technology
Jet Propulsion Laboratory
2015-2024
University of Arizona
2024
University of Padua
2024
University of California, Los Angeles
2016-2023
The Aerospace Corporation
2002-2021
Mercer Island School District
2021
Planetary Society
2021
Planetary Science Institute
2016
California Institute of Technology
2004-2015
Lomonosov Moscow State University
1997-2013
Analyses of laser ranges to the Moon provide increasingly stringent limits on any violation Equivalence Principle (EP); they also enable several very accurate tests relativistic gravity. We report results our recent analysis Lunar Laser Ranging (LLR) data giving an EP test \Delta (M_G/M_I)_{EP} =(-1.0 +/- 1.4) x 10^{-13}. This result yields a Strong (SEP) (M_G/M_I)_{SEP} =(-2.0 2.0) Also, corresponding SEP parameter \eta is (4.4 4.5) 10^{-4}, where \eta=4\beta-\gamma-3 and both \beta \gamma...
Our previous analyses of radio Doppler and ranging data from distant spacecraft in the solar system indicated that an apparent anomalous acceleration is acting on Pioneer 10 11, with a magnitude ${a}_{P}\ensuremath{\sim}8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8} {\mathrm{c}\mathrm{m}/\mathrm{s}}^{2},$ directed towards Sun. Much effort has been expended looking for possible systematic origins residuals, but none found. A detailed investigation effects both external to internal...
Radio metric data from the Pioneer 10/11, Galileo, and Ulysses spacecraft indicate an apparent anomalous, constant, acceleration acting on with a magnitude $\ensuremath{\sim}8.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}\mathrm{cm}/{\mathrm{s}}^{2}$, directed towards Sun. Two independent codes physical strategies have been used to analyze data. A number of potential causes ruled out. We discuss future kinematic tests possible origins signal.
We investigate the possibility that anomalous acceleration of Pioneer 10 and 11 spacecraft is due to recoil force associated with an anisotropic emission thermal radiation off vehicles. To this end, relying on project design documentation, we constructed a comprehensive finite-element model two spacecraft. Then, numerically solve conduction equations using actual flight telemetry as boundary conditions. use results evaluate effect at various heliocentric distances. found magnitude, temporal...
The Lunar Laser Ranging (LLR) experiment provides precise observations of the lunar orbit that contribute to a wide range science investigations. In particular, time series highly accurate measurements distance between Earth and Moon provide unique information determine whether, in accordance with Equivalence Principle (EP), both these celestial bodies are falling towards Sun at same rate, despite their different masses, compositions, gravitational self-energies. Analyses laser ranges...
Einstein's general theory of relativity is the standard gravity, especially where needs astronomy, astrophysics, cosmology and fundamental physics are concerned. As such, this used for many practical purposes involving spacecraft navigation, geodesy, time transfer. Here I review foundations relativity, discuss recent progress in tests relativistic gravity solar system, present motivations new generation high-accuracy gravitational experiments. advances our understanding that anticipated near...
A primary objective of the lunar laser ranging (LLR) experiment is to provide precise observations orbit that contribute a wide range science investigations. In particular, time series highly accurate measurements distance between Earth and Moon unique information used determine whether, in accordance with equivalence principle (EP), these two celestial bodies are falling toward Sun at same rate, despite their different masses, compositions, gravitational self-energies. Thirty-five years...
Einstein's general theory of relativity is the standard gravity, especially where needs astronomy, astrophysics, cosmology and fundamental physics are concerned. As such, this used for many practical purposes involving spacecraft navigation, geodesy time transfer. Here I review foundations relativity, discuss recent progress in tests relativistic present motivations new generation high-accuracy beyond relativity. Space-based experiments capable today to uniquely address important questions...
We consider the propagation of electromagnetic (EM) waves in gravitational field Sun within first post-Newtonian approximation general theory relativity. solve Maxwell's equations for EM propagating on background a static mass monopole and find an exact closed form solution Debye potentials, which, turn, yield to problem diffraction Sun. The is given terms confluent hypergeometric function and, as such, it valid all distances angles. Using this solution, we develop wave-theoretical...
The small satellite 'Galileo Galilei' (GG) will test the universality of free fall and hence weak equivalence principle which is founding pillar general relativity to 1 part in 1017. It use proof masses whose atoms differ substantially from one another their mass energy content, so as maximize chance violation. GG improve by four orders magnitude current best 'Eöt-Wash' tests based on slowly rotating torsion balances, have been able reach thermal noise level. In GG, expected violation signal...
The Pioneer anomaly is a small sunward anomalous acceleration found in the trajectory analysis of 10 and 11 spacecraft. As part investigation effect, recently recovered Doppler data for both spacecraft has been completed. presence confirmed using spans more than twice as long those that were previously analyzed. We examine constancy direction anomaly, conclude that: i) favor temporally decaying (~2\times 10^{-11} m/s^2/yr) with an over 10% improvement residuals compared to constant model;...
We present initial results of an ongoing engineering study on the feasibility a space mission to focal region solar gravitational lens (SGL). The goal is conduct exoplanet imaging operations at heliocentric distances in range ~548-900 astronomical units (AU). Starting 548 AU from Sun, light located behind Sun greatly amplified by SGL. objective capture this and use it for multipixel up 100 years distant. Using meter-class telescope one can produce images with surface resolution measured tens...
We investigate light propagation in the gravitational field of multiple lenses. Assuming these lenses are sufficiently spaced to prevent interaction, we consider a linear alignment for transmitter, lenses, and receiver. Remarkably, this axially symmetric configuration, can solve relevant diffraction integrals---result that offers valuable analytical insights. show point-spread function (PSF) is affected by number system. Even single lens useful transmission either it used as part transmitter...
We present a high-power continuous-wave (CW) lunar laser ranging (LLR) technique that has the potential to significantly improve Earth--Moon distance measurements. Using 1 kW CW at 1064 nm and m-aperture telescope as an example, we develop detailed link budget analyze prevailing noise sources assess system performance when next-generation ~10 cm corner-cube retroreflectors (CCRs). Unlike legacy arrays, these smaller CCRs are designed yield lower intrinsic range errors, yet their reduced...
Accurate analysis of precision ranges to the Moon has provided several tests gravitational theory including Equivalence Principle, geodetic precession, parameterized post-Newtonian (PPN) parameters γ and β, constancy constant G. Since beginning experiment in 1969, uncertainties these have decreased considerably as data accuracies improved time span lengthened. We are exploring modeling improvements necessary proceed from cm mm range enabled by new Apache Point Observatory Lunar Laser-ranging...
This paper discusses new fundamental physics experiment to test relativistic gravity at the accuracy better than effects of 2nd order in gravitational field strength. The Laser Astrometric Test Of Relativity (LATOR) mission uses laser interferometry between two micro-spacecraft whose lines sight pass close by Sun accurately measure deflection light solar gravity. key element experimental design is a redundant geometry optical truss provided long-baseline (100 m) multi-channel stellar...
The Pioneer 10/11 spacecraft yielded the most precise navigation in deep space to date. However, their radiometric tracking data has consistently indicated presence of a small, anomalous, Doppler frequency drift. drift is blue shift, uniformly changing with rate ~6 × 10 -9 Hz/s and can be interpreted as constant sunward acceleration each particular P = (8.74±1.33) -10 m/s 2 (or, alternatively, time t (2.92±0.44) -18 s/s ). This signal become known anomaly; nature this anomaly remains...