The Experts below are selected from a list of 180 Experts worldwide ranked by ideXlab platform
François Barlier - One of the best experts on this subject based on the ideXlab platform.
-
The rotation of LAGEOS and its long‐term semimajor axis decay: A self‐consistent solution
Journal of Geophysical Research: Solid Earth, 1996Co-Authors: Paolo Farinella, David Vokrouhlicky, François BarlierAbstract:We develop a self-consistent model for the evolution of the spin axis of LAGEOS and the related long-term semimajor axis perturbations, due to asymmetric emission/reflection of radiation from the satellite's surface. We show that the theory developed by Bertotti and Iess [1991] for the evolution of LAGEOS's rotation under magnetic and gravitational torques, which we have somewhat generalized here, can lead to a successful fit of the observed semimajor axis residuals, provided the correct initial conditions for the direction of the spin axis are chosen. The remaining residuals have an rms dispersion of 0.50 × 10−12 m/s2, comparable to that of previous solutions, based on purely empirical fits of the spin axis direction as a function of time. The spectrum of the residuals indicates that they are probably due to unmodeled radiation forces (e.g., from Earth Albedo and/or penumbra passages). Our solution allows us to predict the future evolution of LAGEOS's rotation for about another decade in the future, until the spin rate will become so slow that some basic assumptions of the theory will fail. A similar model can also be used to model/predict the coupled spin-orbit evolution of the LAGEOS II satellite, launched in late 1992, although the available data still cover a span of time too short for reaching significant quantitative conclusions concerning this satellite.
-
the rotation of lageos and its long term semimajor axis decay a self consistent solution
Journal of Geophysical Research, 1996Co-Authors: Paolo Farinella, David Vokrouhlicky, François BarlierAbstract:We develop a self-consistent model for the evolution of the spin axis of LAGEOS and the related long-term semimajor axis perturbations, due to asymmetric emission/reflection of radiation from the satellite's surface. We show that the theory developed by Bertotti and Iess [1991] for the evolution of LAGEOS's rotation under magnetic and gravitational torques, which we have somewhat generalized here, can lead to a successful fit of the observed semimajor axis residuals, provided the correct initial conditions for the direction of the spin axis are chosen. The remaining residuals have an rms dispersion of 0.50 × 10−12 m/s2, comparable to that of previous solutions, based on purely empirical fits of the spin axis direction as a function of time. The spectrum of the residuals indicates that they are probably due to unmodeled radiation forces (e.g., from Earth Albedo and/or penumbra passages). Our solution allows us to predict the future evolution of LAGEOS's rotation for about another decade in the future, until the spin rate will become so slow that some basic assumptions of the theory will fail. A similar model can also be used to model/predict the coupled spin-orbit evolution of the LAGEOS II satellite, launched in late 1992, although the available data still cover a span of time too short for reaching significant quantitative conclusions concerning this satellite.
C B Markwardt - One of the best experts on this subject based on the ideXlab platform.
-
cosmic x ray background and Earth Albedo spectra with swift bat
The Astrophysical Journal, 2008Co-Authors: M Ajello, J Greiner, G Sato, D R Willis, G Kanbach, A W Strong, R Diehl, G Hasinger, N Gehrels, C B MarkwardtAbstract:We use Swift/BAT Earth occultation data at different geomagnetic latitudes to derive a sensitive measurement of the Cosmic X-ray background (CXB) and of the Earth Albedo emission in the 15–200keV band. We compare our CXB spectrum with recent (INTEGRAL, BeppoSAX) and past results (HEAO-1) and find good agreement. Using an independent measurement of the CXB spectrum we are able to confirm our results. This study shows that the BAT CXB spectrum has a normalization � 8 ± 3% larger than the HEAO-1 measurement. The BAT accurate Earth Albedo spectrum can be used to predict the level of photon background for satellites in low Earth and mid inclination orbits.
-
Cosmic X-ray background and Earth Albedo Spectra with Swift/BAT
The Astrophysical Journal, 2008Co-Authors: M Ajello, J Greiner, G Sato, D R Willis, G Kanbach, A W Strong, R Diehl, G Hasinger, N Gehrels, C B MarkwardtAbstract:We use Swift/BAT Earth occultation data at different geomagnetic latitudes to derive a sensitive measurement of the Cosmic X-ray background (CXB) and of the Earth Albedo emission in the 15--200 keV band. We compare our CXB spectrum with recent (INTEGRAL, BeppoSAX) and past results (HEAO-1) and find good agreement. Using an independent measurement of the CXB spectrum we are able to confirm our results. This study shows that the BAT CXB spectrum has a normalization ~8(+/-3)% larger than the HEAO-1 measurement. The BAT accurate Earth Albedo spectrum can be used to predict the level of photon background for satellites in low Earth and mid inclination orbits.
M Ajello - One of the best experts on this subject based on the ideXlab platform.
-
Fermi Large Area Telescope Observations of the Cosmic-Ray Induced gamma-ray Emission of the Earth's Atmosphere
Physical Review D, 2009Co-Authors: A. A. Abdo, M Ajello, Markus Ackermann, W. B. Atwood, Luca Baldini, Jean Ballet, Guido Barbiellini, D. Bastieri, B. M. Baughman, K. BechtolAbstract:We report on measurements of the cosmic-ray induced gamma-ray emission of Earth's atmosphere by the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope. The LAT has observed the Earth during its commissioning phase and with a dedicated Earth-limb following observation in September 2008. These measurements yielded 6.4 x 10^6 photons with energies >100MeV and ~250hours total livetime for the highest quality data selection. This allows the study of the spatial and spectral distributions of these photons with unprecedented detail. The spectrum of the emission - often referred to as Earth Albedo gamma-ray emission - has a power-law shape up to 500 GeV with spectral index Gamma = 2.79+-0.06.
-
cosmic x ray background and Earth Albedo spectra with swift bat
The Astrophysical Journal, 2008Co-Authors: M Ajello, J Greiner, G Sato, D R Willis, G Kanbach, A W Strong, R Diehl, G Hasinger, N Gehrels, C B MarkwardtAbstract:We use Swift/BAT Earth occultation data at different geomagnetic latitudes to derive a sensitive measurement of the Cosmic X-ray background (CXB) and of the Earth Albedo emission in the 15–200keV band. We compare our CXB spectrum with recent (INTEGRAL, BeppoSAX) and past results (HEAO-1) and find good agreement. Using an independent measurement of the CXB spectrum we are able to confirm our results. This study shows that the BAT CXB spectrum has a normalization � 8 ± 3% larger than the HEAO-1 measurement. The BAT accurate Earth Albedo spectrum can be used to predict the level of photon background for satellites in low Earth and mid inclination orbits.
-
Cosmic X-ray background and Earth Albedo Spectra with Swift/BAT
The Astrophysical Journal, 2008Co-Authors: M Ajello, J Greiner, G Sato, D R Willis, G Kanbach, A W Strong, R Diehl, G Hasinger, N Gehrels, C B MarkwardtAbstract:We use Swift/BAT Earth occultation data at different geomagnetic latitudes to derive a sensitive measurement of the Cosmic X-ray background (CXB) and of the Earth Albedo emission in the 15--200 keV band. We compare our CXB spectrum with recent (INTEGRAL, BeppoSAX) and past results (HEAO-1) and find good agreement. Using an independent measurement of the CXB spectrum we are able to confirm our results. This study shows that the BAT CXB spectrum has a normalization ~8(+/-3)% larger than the HEAO-1 measurement. The BAT accurate Earth Albedo spectrum can be used to predict the level of photon background for satellites in low Earth and mid inclination orbits.
Paolo Farinella - One of the best experts on this subject based on the ideXlab platform.
-
The rotation of LAGEOS and its long‐term semimajor axis decay: A self‐consistent solution
Journal of Geophysical Research: Solid Earth, 1996Co-Authors: Paolo Farinella, David Vokrouhlicky, François BarlierAbstract:We develop a self-consistent model for the evolution of the spin axis of LAGEOS and the related long-term semimajor axis perturbations, due to asymmetric emission/reflection of radiation from the satellite's surface. We show that the theory developed by Bertotti and Iess [1991] for the evolution of LAGEOS's rotation under magnetic and gravitational torques, which we have somewhat generalized here, can lead to a successful fit of the observed semimajor axis residuals, provided the correct initial conditions for the direction of the spin axis are chosen. The remaining residuals have an rms dispersion of 0.50 × 10−12 m/s2, comparable to that of previous solutions, based on purely empirical fits of the spin axis direction as a function of time. The spectrum of the residuals indicates that they are probably due to unmodeled radiation forces (e.g., from Earth Albedo and/or penumbra passages). Our solution allows us to predict the future evolution of LAGEOS's rotation for about another decade in the future, until the spin rate will become so slow that some basic assumptions of the theory will fail. A similar model can also be used to model/predict the coupled spin-orbit evolution of the LAGEOS II satellite, launched in late 1992, although the available data still cover a span of time too short for reaching significant quantitative conclusions concerning this satellite.
-
the rotation of lageos and its long term semimajor axis decay a self consistent solution
Journal of Geophysical Research, 1996Co-Authors: Paolo Farinella, David Vokrouhlicky, François BarlierAbstract:We develop a self-consistent model for the evolution of the spin axis of LAGEOS and the related long-term semimajor axis perturbations, due to asymmetric emission/reflection of radiation from the satellite's surface. We show that the theory developed by Bertotti and Iess [1991] for the evolution of LAGEOS's rotation under magnetic and gravitational torques, which we have somewhat generalized here, can lead to a successful fit of the observed semimajor axis residuals, provided the correct initial conditions for the direction of the spin axis are chosen. The remaining residuals have an rms dispersion of 0.50 × 10−12 m/s2, comparable to that of previous solutions, based on purely empirical fits of the spin axis direction as a function of time. The spectrum of the residuals indicates that they are probably due to unmodeled radiation forces (e.g., from Earth Albedo and/or penumbra passages). Our solution allows us to predict the future evolution of LAGEOS's rotation for about another decade in the future, until the spin rate will become so slow that some basic assumptions of the theory will fail. A similar model can also be used to model/predict the coupled spin-orbit evolution of the LAGEOS II satellite, launched in late 1992, although the available data still cover a span of time too short for reaching significant quantitative conclusions concerning this satellite.
David Vokrouhlicky - One of the best experts on this subject based on the ideXlab platform.
-
The rotation of LAGEOS and its long‐term semimajor axis decay: A self‐consistent solution
Journal of Geophysical Research: Solid Earth, 1996Co-Authors: Paolo Farinella, David Vokrouhlicky, François BarlierAbstract:We develop a self-consistent model for the evolution of the spin axis of LAGEOS and the related long-term semimajor axis perturbations, due to asymmetric emission/reflection of radiation from the satellite's surface. We show that the theory developed by Bertotti and Iess [1991] for the evolution of LAGEOS's rotation under magnetic and gravitational torques, which we have somewhat generalized here, can lead to a successful fit of the observed semimajor axis residuals, provided the correct initial conditions for the direction of the spin axis are chosen. The remaining residuals have an rms dispersion of 0.50 × 10−12 m/s2, comparable to that of previous solutions, based on purely empirical fits of the spin axis direction as a function of time. The spectrum of the residuals indicates that they are probably due to unmodeled radiation forces (e.g., from Earth Albedo and/or penumbra passages). Our solution allows us to predict the future evolution of LAGEOS's rotation for about another decade in the future, until the spin rate will become so slow that some basic assumptions of the theory will fail. A similar model can also be used to model/predict the coupled spin-orbit evolution of the LAGEOS II satellite, launched in late 1992, although the available data still cover a span of time too short for reaching significant quantitative conclusions concerning this satellite.
-
the rotation of lageos and its long term semimajor axis decay a self consistent solution
Journal of Geophysical Research, 1996Co-Authors: Paolo Farinella, David Vokrouhlicky, François BarlierAbstract:We develop a self-consistent model for the evolution of the spin axis of LAGEOS and the related long-term semimajor axis perturbations, due to asymmetric emission/reflection of radiation from the satellite's surface. We show that the theory developed by Bertotti and Iess [1991] for the evolution of LAGEOS's rotation under magnetic and gravitational torques, which we have somewhat generalized here, can lead to a successful fit of the observed semimajor axis residuals, provided the correct initial conditions for the direction of the spin axis are chosen. The remaining residuals have an rms dispersion of 0.50 × 10−12 m/s2, comparable to that of previous solutions, based on purely empirical fits of the spin axis direction as a function of time. The spectrum of the residuals indicates that they are probably due to unmodeled radiation forces (e.g., from Earth Albedo and/or penumbra passages). Our solution allows us to predict the future evolution of LAGEOS's rotation for about another decade in the future, until the spin rate will become so slow that some basic assumptions of the theory will fail. A similar model can also be used to model/predict the coupled spin-orbit evolution of the LAGEOS II satellite, launched in late 1992, although the available data still cover a span of time too short for reaching significant quantitative conclusions concerning this satellite.
