Acceleration disturbances due to local gravity gradients in ASTROD I

The Astrodynamical Space Test of Relativity using Optical Devices (ASTROD) mission consists of three spacecraft in separate solar orbits and carries out laser interferometric ranging. ASTROD aims at testing relativistic gravity, measuring the solar system and detecting gravitational waves. Because of the larger arm length, the sensitivity of ASTROD to gravitational waves is estimated to be about 30 times better than Laser Interferometer Space Antenna (LISA) in the frequency range lower than about 0.1 mHz. ASTROD I is a simple version of ASTROD, employing one spacecraft in a solar orbit. It is the first step for ASTROD and serves as a technology demonstration mission for ASTROD. In addition, several scientific results are expected in the ASTROD I experiment. The required acceleration noise level of ASTROD I is 10^-13 m s^-2 Hz^{-1/2} at the frequency of 0.1 mHz. In this paper, we focus on local gravity gradient noise that could be one of the largest acceleration disturbances in the ASTROD I experiment. We have carried out gravitational modelling for the current test-mass design and simplified configurations of ASTROD I by using an analytical method and the Monte Carlo method. Our analyses can be applied to figure out the optimal designs of the test mass and the constructing materials of the spacecraft, and the configuration of compensation mass to reduce local gravity gradients.Comment: 6 pages, presented at the 6th Edoardo Amaldi Conference (Okinawa Japan, June 2005); to be published in Journal of Physics: Conference Serie

ASTROD, ASTROD I and their gravitational-wave sensitivities

ASTROD (Astrodynamical Space Test of Relativity using Optical Devices) is a mission concept with three spacecraft -- one near L1/L2 point, one with an inner solar orbit and one with an outer solar orbit, ranging coherently with one another using lasers to test relativistic gravity, to measure the solar system and to detect gravitational waves. ASTROD I with one spacecraft ranging optically with ground stations is the first step toward the ASTROD mission. In this paper, we present the ASTROD I payload and accelerometer requirements, discuss the gravitational-wave sensitivities for ASTROD and ASTROD I, and compare them with LISA and radio-wave PDoppler-tracking of spacecraft.Comment: presented to the 5th Edoardo Amaldi Conference (July 6-11, 2003) and submitted to Classical and Quantum Gravit

Acceleration disturbances and requirements for ASTROD I

ASTRODynamical Space Test of Relativity using Optical Devices I (ASTROD I) mainly aims at testing relativistic gravity and measuring the solar-system parameters with high precision, by carrying out laser ranging between a spacecraft in a solar orbit and ground stations. In order to achieve these goals, the magnitude of the total acceleration disturbance of the proof mass has to be less than 10−13 m s−2 Hz−1/2 at 0.1 m Hz. In this paper, we give a preliminary overview of the sources and magnitude of acceleration disturbances that could arise in the ASTROD I proof mass. Based on the estimates of the acceleration disturbances and by assuming a simple controlloop model, we infer requirements for ASTROD I. Our estimates show that most of the requirements for ASTROD I can be relaxed in comparison with Laser Interferometer Space Antenna (LISA).Comment: 19 pages, two figures, accepted for publication by Class. Quantum Grav. (at press

Orbit optimization for ASTROD-GW and its time delay interferometry with two arms using CGC ephemeris

ASTROD-GW (ASTROD [Astrodynamical Space Test of Relativity using Optical Devices] optimized for Gravitation Wave detection) is an optimization of ASTROD to focus on the goal of detection of gravitation waves. The detection sensitivity is shifted 52 times toward larger wavelength compared to that of LISA. The mission orbits of the 3 spacecraft forming a nearly equilateral triangular array are chosen to be near the Sun-Earth Lagrange points L3, L4 and L5. The 3 spacecraft range interferometrically with one another with arm length about 260 million kilometers. In order to attain the requisite sensitivity for ASTROD-GW, laser frequency noise must be suppressed below the secondary noises such as the optical path noise, acceleration noise etc. For suppressing laser frequency noise, we need to use time delay interferometry (TDI) to match the two different optical paths (times of travel). Since planets and other solar-system bodies perturb the orbits of ASTROD-GW spacecraft and affect the (TDI), we simulate the time delay numerically using CGC 2.7 ephemeris framework. To conform to the ASTROD-GW planning, we work out a set of 20-year optimized mission orbits of ASTROD-GW spacecraft starting at June 21, 2028, and calculate the residual optical path differences in the first and second generation TDI for one-detector case. In our optimized mission orbits for 20 years, changes of arm length are less than 0.0003 AU; the relative Doppler velocities are less than 3m/s. All the second generation TDI for one-detector case satisfies the ASTROD-GW requirement.Comment: 17 pages, 7 figures, 1 tabl

Asteroidal

The DENIS programme (Deep European Near-Infrared Southern Sky Survey) has carried out a ground-based survey of the southern sky to provide an extensive I, J, K photometric catalog of point and extended sources. The limiting magnitudes of the three bands I, J, K centered at 0.8, 1.25 and 2.15 μm are respectively 18.5, 16.5 and 13.5. Given the short exposure time of the observations, asteroids have been included in the point source catalog as any other regular point-like object. We have searched the first 8000 asteroids on the basis of their predicted positions following a recognition procedure described previously (Baudrand et al. [CITE]); in this first release based on the DENIS data available in January 2001 we recovered 1233 asteroids. We present here the second release which provides 767 asteroids. Their I, J, K magnitudes are compiled in electronic tables available at the CDS

Ephémérides des satellites faibles de Jupiter et de Saturne pour 1996

In the following tables are given the ephemerides of the satellites J VI, J VII, J VIII and J IX of Jupiter, and of the satellite Phoebe (S IX) of Saturn. These ephemerides come from numerical integration of the G.B.S. type (Gragg-Bulirsch-Stoer, 1966). The numerical constants of integration have been corrected by comparison with the observations (for J VI, JVII, J VIII and J IX : P. Eocher, 1993, for Phcebe : A. Bec-Borsenberger and P. Rocher, 1982). The published quantities are equatorial, geocentric and astrometric coordinates. For each year, we find successively the ephemerides for J VI, J VII, J VIII ,J IX, Jupiter and Phoebe developed into Chebyshev series. Each development covers 33 days beginning by the day before the first day in the month, numbered zero. The developments contain 10 coefficients, numbered from zero to nine, the value above the table of coefficients corresponds to the starting date in the given interval of time. The right ascension is expressed in hour, the declination in degree and the distance in au. The argument of the series is the terrestrial time (TT) The planetary ephemerides have been computed from BDL82 (B.D.L. ephemerides). The published coefficients are such that precision of 0.01 second of time in right ascension, 0.1 second of degree in declination and 1.10-6 au in distance, is obtained. This supplement will be published every year, with eventually new satellites.Une plus grande facilité actuelle d’observation des satellites faibles du système solaire nous a incités à élaborer des éphémérides pour ceux-ci. Dans un premier temps, nous proposons des éphémérides des satellites J VI, J VII, J VIII et J IX de Jupiter et du satellite Phœbé (S IX) de Saturne. Ces éphémérides sont obtenues à partir d’intégrations numériques et publiées sous Ia forme de séries de polynômes de TchebychefF, présentation utilisée dans Ia Con­naissance des Temps depuis 1980. Les observations de ces satellites étant essentiellement photographiques, nous publions leurs coordonnées astrométriques géocentriques. Pour permettre un passage à des coordonnées différentielles dans Ie cas des satellites de Jupiter, nous publions également les éphémérides de celui-ci dans Ie même système de coordonnées ; dans Ie cas de Phœbé, nous donnons directement les coordonnées du satellite par rapport à Saturne. Nous présentons tout d’abord un tableau des caractéristiques des satellites de Jupiter et de Saturne, dont nous donnons ici les éphémérides.Ce supplément sera édité tous les ans avec, éventuellement, adjonction de nouveaux satellites. L’ensemble des calculs a été réalisé sur un PC486, pour les satellites de Jupiter, et sur une Vax station 4000.60 pour Phoebé

Ephémérides des satellites faibles de Jupiter et de Saturne pour 1990

In the following tables are given the ephemerides of the satellites J VI, J VII, J VIII and J IX of Jupiter, and of the satellite Phoebe (S IX) of Saturn. These ephemerides come from numerical integration of the G.B.S. type (Gragg-Bulirsch-Stoer, 1966).The numerical constants of integration are those used by T.V. Bordovystina and L.E. Bykova (1978) for J VI and J VII, by K.A. Aksnes (1973) for J VIII and J IX and by L.E. Rose (1979) for Phoebe. For these satellites, these constants are adjusted by comparison with the observations. The published quantities are equatorial, geocentric and astrometric coordinates. For each year, we find successively the ephemerides for J VI, J VII, J VIII ,J IX, Jupiter and Phoebe developed into Chebyshev series. Each development covers 33 days beginning by the day before the first day in the month, numbered zero. The developments contain 10 coefficients, numbered from zero to nine, the value above the table of coefficients corresponds to the starting date in the given interval of time. The right ascension is expressed in hour, the declination in degree and the distance in A.U. The argument of the series is the ephemeris time (T.E) expressed in Julian days. The planetary ephemerides have been computed from DEl02 (J.P.L. ephemerides).The published coefficients are such that precision of 0.01 second of time in right ascension, 0.1 second of degree in declination and 1.10-6 au in distance, is obtained. This supplement will be published every year, with eventually new satellites.Une plus grande facilité actuelle d’observation des satellites faibles du système solaire nous a incités à élaborer des éphémérides pour ceux-ci.Dans un premier temps, nous proposons des éphémérides des satellites J VI, J VII, J VIII et J IX de Jupiter et du satellite Phœbé (S IX) de Saturne. Ces éphémérides sont obtenues à partir d’intégrations numériques et publiées sous Ia forme de séries de polynômes de Tchebycheff, présentation utilisée dans Ia Connaissance des Temps depuis 1980. Les observations de ces satellites étant essentiellement photographiques, nous publions les coordonnées astrométriques géocentriques de ces satellites. Pour per­mettre un passage à des coordonnées différentielles dans Ie cas des satellites de Jupiter, nous publions également les éphémérides de celui-ci dans Ie même système de coordonnées ; dans Ie cas de Phœbé, nous donnons directement les coordonnées du satellite par rapport à Saturne. Nous présentons tout d’abord un tableau des caractéristiques des satellites de Jupiter et de Saturne, dont nous donnons ici les éphémérides.Ce supplément sera édité tous les ans avec, éventuellement, adjonction de nouveaux satellites. L’ensemble des calculs a été réalisé au Centre Inter Régional de Calcul Electronique d’Orsay (CIRCE)

Ephémérides des satellites faibles de Jupiter et de Saturne pour 1989

In the following tables are given the ephemerides of the satellites J VI, J VII, J VIII and J IX of Jupiter, and of the satellite Phoebe (S IX) of Saturn. These ephemerides come from numerical integration of the G.B.S. type (Gragg-Bulirsch-Stoer, 1966).The numerical constants of integration are those used by T.V. Bordovystina and L.E. Bykova (l978) for J VI and J VII, by K.A. Aksnes (1973) for J VIII and J IX and by L.E. Rose(1979) for Phoebe. For these satellites, these constants are adjusted by comparison with the observations. The published quantities are equatorial, geocentric and astrometric coordinates. For each year, we find successively the ephemerides for J VI, J VII, J VIII ,J IX, Jupiter and Phoebe developed into Chebyshev series. Each development covers 33 days beginning by the day before the first day in the month, numbered zero. The developments contain 10 coefficients, numbered from zero to nine, the value above the table of coefficients corresponds to the starting date in the given interval of time. The right ascension days. The planetary ephemerides have been computed from DEl02 (J.P.L. ephemerides). The published coefficients are such that precision of 0.01 second of time in right ascension, 0.1 second of degree in declination and 1.10~6 A.U in distance, is obtained. This supplement will be published every is expressed in hour, the declination in degree and the distance in A.U. The argument of the series is the ephemeris time (T.E) expressed in Julian year, with eventually new satellites.Une plus grande facilité actuelle d’observation des satellites faibles du système solaire nous a incités à élaborer des éphémérides pour ceux-ci.Dans un premier temps, nous proposons des éphémérides des satellites J VI, J VII, J VIII et J IX de Jupiter et du satellite Phœbé(S IX) de Saturne. Ces éphémérides sont obtenues à partir d’intégrations numériques et publiées sous Ia forme de séries de polynômes de Tchebycheff, présentation utilisée dans Ia Connaissance des Temps depuis 1980. Les observations de ces satellites étant essentiellement pho­tographiques, nous publions les coordonnées astrométriques géocentriques de ces satellites. Pour per­mettre un passage à des coordonnées différentielles dans Ie cas des satellites de Jupiter, nous publions également les éphémérides de celui-ci dans Ie même système de coordonnées; dans Ie cas de Phœbé, nous donnons directement les coordonnées du satellite par rapport à Saturne. Nous présentons tout d’abord un tableau des caractéristiques des satellites de Jupiter et de Saturne, dont nous donnons ici les éphémérides.Ce supplément sera édité tous les ans avec, éventuellement, adjonction de nouveaux satellites.L’ensemble des calculs a été réalisé au Centre Inter Régional de Calcul Electronique d’Orsay (CIRCE)

Ephémérides des satellites faibles de Jupiter et de Saturne pour 1994

In the following tables are given the ephemerides of the satellites J VI, J VII, J VIII and J IX of Jupiter, and of the satellite Phoebe (S IX) of Saturn. These ephemerides come from numerical integration of the G.B.S. type (Gragg-Bulirsch-Stoer, 1966).The numerical constants of integration are those used by T.V. Bordovystina and L.E. Bykova (1978) for J VI and J VII, by K.A. Aksnes (1973) for J VIII and J IX and by L.E. Rose (1979) for Phoebe. For these satellites, these constants have been corrected by comparison with the observations. The published quantities are equatorial, geocentric and astrometric coordinates. For each year, we find successively the ephemerides for J VI, J VII, J VIII ,J IX, Jupiter and Phoebe developed into Chebyshev series. Each development covers 33 days beginning by the day before the first day in the month, numbered zero. The developments contain 10 coefficients, numbered from zero to nine, the value above the table of coefficients corresponds to the starting date in the given interval of time. The right ascension is expressed in hour, the declination in degree and the distance in au. The argument of the series is the terrestrial time (TT) The planetary ephemerides have been computed from BDL82 (B.D.L. ephemerides).The published coefficients are such that precision of 0.01 second of time in right ascension, 0.1 second of degree in declination and 1.10-6 au in distance, is obtained. This supplement will be published every year, with eventually new satellites.Une plus grande facilité actuelle d’observation des satellites faibles du système solaire nous a incités à élaborer des éphémérides pour ceux-ci.Dans un premier temps, nous proposons des éphémérides des satellites J VI, J VII, J VIII et J IX de Jupiter et du satellite Phœbé(S IX) de Saturne. Ces éphémérides sont obtenues à partir d’intégrations numériques et publiées sous Ia forme de séries de polynômes de Tchebycheff, présentation utilisée dans Ia Con­naissance des Temps depuis 1980. Les observations de ces satellites étant essentiellement photographiques, nous publions leurs coordonnées astrométriques géocentriques. Pour permettre un passage à des coordonnées différentielles dans Ie cas des satellites de Jupiter, nous publions également les éphémérides de celui-ci dans Ie même système de coordonnées ; dans Ie cas de Phœbé, nous donnons directement les coordonnées du satellite par rapport à Saturne. Nous présentons tout d’abord un tableau des caractéristiques des satellites de Jupiter et de Saturne, dont nous donnons ici les éphémérides.Ce supplément sera édité tous les ans avec, éventuellement, adjonction de nouveaux satellites.L’ensemble des calculs a été réalisé sur un PC486, pour les satellites de Jupiter, et sur une Vax station 4000.60 pour Phoebé