A5024099958- Planetary Science and Exploration
- Geophysics and Gravity Measurements
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Adaptive optics and wavefront sensing
- Spacecraft Design and Technology
- Space Exploration and Technology
- GNSS positioning and interference
- Inertial Sensor and Navigation
- Space Satellite Systems and Control
- Solar and Space Plasma Dynamics
- History and Developments in Astronomy
- Spacecraft and Cryogenic Technologies
- Space Science and Extraterrestrial Life
- CCD and CMOS Imaging Sensors
- Gamma-ray bursts and supernovae
- Relativity and Gravitational Theory
- Astrophysics and Star Formation Studies
- Geophysics and Sensor Technology
- Advanced Measurement and Metrology Techniques
- Space exploration and regulation
- Advanced Frequency and Time Standards
- Geomagnetism and Paleomagnetism Studies
University of Maryland, College Park
2014-2025
Istituto Nazionale di Fisica Nucleare
2010-2022
Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati
2010-2018
Solar System Exploration Research Virtual Institute
2010-2013
Joint Space Science Institute
2013
Ames Research Center
2010
European Southern Observatory
2002
Joint Institute for Laboratory Astrophysics
1976
University of Hawaii System
1976
Jet Propulsion Laboratory
1976
Relativistic invariance may involve two different theoretical postulates: symmetry of the theory under relativistic transformation group reflecting physical laws changes reference frame, and explicit properties or manifest certain quantities. A Lie formalism, for classical quantum mechanics particle variables fields, is introduced used to show how Lorentz (or Galilei) provided by ten generators satisfying characteristic bracket equations. For a mechanical fixed number particles,...
We present Hubble Space Telescope WFPC2 images of elephant trunks in the H II region M16. There are three principle results this study. First, morphology and stratified ionization structure interface between dense molecular material interior is well understood terms photoionization a photoevaporative flow. Photoionization models an empirical density profile capture essential features observations, including extremely localized [S II] emission at observed offset peaks lower higher lines. The...
The lunar ranging measurements now being made at the McDonald Observatory have an accuracy of 1 nsec in round-trip travel time. This corresponds to 15 cm one-way distance. use lasers with pulse-lengths less than is expected give 2 3 next few years. A new station under construction Hawaii, and additional stations other countries are either operation or development. It hoped that these will form basis for a worldwide network determine polar motion earth rotation on regular basis, assist...
An analysis of six years lunar-laser-ranging data gives a zero amplitude for the Nordtvedt term in Earth-Moon distance yielding parameter $\ensuremath{\eta}=0.00\ifmmode\pm\else\textpm\fi{}0.03$ Thus, Earth's gravitational self-energy contributes equally, \ifmmode\pm\else\textpm\fi{}3%, to its inertial mass and passive mass. At 70% confidence level this result is only consistent with Brans-Dicke theory $\ensuremath{\omega}>29$. We obtain...
The relativistic Hamiltonian formalism is outlined and discussed for classical particles. implications of the requirement that coordinates an event transform according to Lorentz transformation law are expressed in a form, called world-line conditions, which may be considered formalism. It then shown conditions imply there no interaction formalism; is, motion any pair particles described by consists straightline motion. In other words, if events compose world lines law, path particle not...
Classical particles, and interaction among them governed by second-order equations of motion for the positions are considered. Equations motion, defined one instant in an arbitrary frame, derived which invariant under Poincar\'e group. The considered if, when world-line solutions to transformed, point point, into a new world lines obey same equation motion. We illustrate existence wide class such further questions causality separability mentioned.
The classes of equivalent Lagrangians in one-dimensional particle dynamics are found. These contain not only yielding the same equations motion (Lagrangians differing by a total time derivative), but also those implying each other's motion. corresponding Hamiltonians, all which give orbits configuration space, general different phase Some specific examples presented.
It is proved that every density matrix the limit, in sense of weak operator convergence, a sequence operators each which may be represented as an integral over projection onto coherent states (in Glauber) with square-integrable weight function. This result special case one holds for all trace and overcomplete families other than just states. We prove our more general result, at no cost complexity, within framework continuous-representation theory. The significance results representing traces...
Since 1969, 55 years ago, Lunar Laser Ranging (LLR) has provided accurate and precise (down to ~1 cm RMS) measurements of the Moon’s orbit thanks Apollo Lunokhod Cube Corner Retroreflector (CCR) Arrays (LRAs) deployed on Moon. Nowadays, current level precision these is largely limited by lunar librations affecting old generation LRAs. To improve this situation, next-generation libration-free retroreflectors are necessary. end, Satellite/lunar/GNSS laser ranging/altimetry cube/microsat...
StarFinder is a new code for the deep analysis of stellar fields, designed well-sampled images with high and low Strehl ratio. It organized in form self-contained IDL widget-based application, 'user-friendly' graphic interface. We give here general description along some applications to real data space-invariant Point Spread Function (PSF). present also methods handle anisoplanatic effects wide-field Adaptive Optics (AO)observations.
We have investigated the potential accuracy with which distances between 12 observing stations that are spread fairly uniformly over earth can be determined by using laser range measurements to a high-altitude satellite equipped optical retro-reflectors. For each of 30 positions, it was assumed were made at about same time from 4 closest stations. ideal distribution stations, expected uncertainty in distance any 2 found less than 45 cm, little dependence on altitude 20,000–110,000 km. With...
view Abstract Citations (104) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Astrometric Analysis of the Homunculus eta Carinae With Hubble Space Telescope Currie, Douglas G. ; Dowling, Daniel M. Shaya, Edward J. Hester, Jeff Scowen, Paul Groth, Lynds, Roger O'neil, Earl J., Jr. Wide Field/Planetary Camera Instrument Definition Team Images η Carinae, obtained with HST in 1990 October (WFl), 1991 April (PC 1), and 1992 December (WF2) have...
view Abstract Citations (71) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Four stellar-diameter measurements by a new technique: amplitude interferometry. Currie, D. G. ; Knapp, S. L. Liewer, K. M. Diameters are reported for four late-type giant stars, Boo, Ori, Tau, and p Peg. The diameters were obtained with kind of interferometer designed expressly to operate in the presence atmospheric fluctuations. technique, called interferometry, is...
Abstract The Lunar Geophysical Network (LGN) mission is proposed to land on the Moon in 2030 and deploy packages at four locations enable geophysical measurements for 6–10 yr. Returning lunar surface with a long-lived network key next step advance planetary science. LGN will greatly expand our primarily Apollo-based knowledge of deep interior by identifying characterizing mantle melt layers, as well core size state. To meet objectives, instrument suite provides complementary seismic,...
Abstract The Lunar Laser Ranging (LLR) retroreflector arrays have been on the Moon for half a century. During that time, laser range uncertainty has improved by factor of 100. Consequently, science results also orders magnitude. New retroreflectors are scheduled to go Commercial Lander Payload Services missions and Geophysical Network mission. new single 10 cm corner cube will not spread pulse during reflection like existing do. Due orbital Earth rotational speeds, there is velocity...
view Abstract Citations (102) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Planetary Camera Observations of the Central Parsec M32 Lauer, Tod R. ; Faber, S. M. Currie, Douglas G. Ewald, P. Groth, Edward J. Hester, Jeff Holtzman, Jon A. Light, Robert O'Neil, Earl J., Jr. Shaya, Westphal, James Analysis V band HST images elliptical galaxy shows that its nucleus is extremely dense and remains unresolved at even diffraction limit. A combined...
After successful acquisition in August of reflected ruby laser pulses from the Apollo 11 ranging retro-reflector (LRRR) with telescopes at Lick and McDonald observatories, repeated measurements round-trip travel time light have been made Observatory September an equivalent range precision +/-2.5 meters. These period observations demonstrated performance LRRR through lunar night during sunlit conditions on moon. Instrumentation activated October has yielded a +/-0.3 meter, improvement to...
The satellites LAGEOS‐I and LAGEOS‐II are essential for the scientific study of various (geo)physical phenomena, such as geocenter motion absolute scale. high quality science products strongly depends on SLR observations that orbit description. Therefore all accelerations experienced by spacecraft need to be modeled accurately possible, thermal radiation forces being one them. Traditionally, this is done estimating so‐called empirical accelerations. However, rotational dynamics in particular...
The estimated median accuracy of 194 single-day determinations the earth's angular position in space is 0.7 millisecond (0.01 arc second). Comparison with classical astronomical results gives agreement to about expected 2-millisecond uncertainty 5-day averages obtained by Bureau International de l'Heure. Little evidence for very rapid variations rotation present data.
We have designed and constructed a ``dispersed Fourier Transform Spectrometer'' (dFTS), consisting of conventional FTS followed by grating spectrometer. By combining these two devices, we negate substantial fraction the sensitivity disadvantage for high resolution, broadband, optical spectroscopy, while preserving many advantages inherent to interferometric spectrometers. In addition, implemented simple inexpensive laser metrology system, which enables very precise calibration interferometer...