comets.dat is an ASCII file of cometary orbital elements prepared at the "Institut de Mecani... more comets.dat is an ASCII file of cometary orbital elements prepared at the "Institut de Mecanique Celeste et de Calcul des Ephemerides" (related to the Bureau des Longitudes, Paris). The research and computing needed to generate comets.dat are funded by the French Ministry of Education. The data can be freely used, provided that their origin (Bureau des longitudes) and the author (P. Rocher) are properly cited. User feed-back is encouraged. Unless otherwise specified, send comments and bug reports to: E-mail : stc@imcce.fr Fax : (33) 1 46 33 28 34 Postal mail : IMCCE - Observatoire de Paris 77 avenue Denfert Rochereau F-75014 PARIS (1 data file).
A new method of approximation is used to represent the motions of minor planets which allows ephe... more A new method of approximation is used to represent the motions of minor planets which allows ephemerides to be built in a very compact form. A numerical integration fitted to observations is first performed covering 150 years. Then, by frequency analysis, an approximation of the solution is realized. The ephemeris of the heliocentric rectangular coordinates of the planet is given
The accuracy of the rigid Earth solution SMART97 is 2?µ as over the time interval (1968, 2023), a... more The accuracy of the rigid Earth solution SMART97 is 2?µ as over the time interval (1968, 2023), accuracy showed by the comparison with a numerical integration using the positions of the Moon, the Sun, and the planets given by DE403. To obtain a nonrigid Earth solution, we use the transfer function of Mathews et al. (2000) and, to keep the
The new two-dimensional receptors permit to improve astrometric observations. The authors applied... more The new two-dimensional receptors permit to improve astrometric observations. The authors applied two different types of these receptors to the observations of fast moving objects of the Solar System. In a first step they have developed a video system where the signal of an intensified vidicon camera is digitized and processed in an array processor. Results have been obtained with this receptor for observations which need high speed photometric or astrometric differential measurements: appulses or occultations of stars by asteroids, mutual events of the Galilean satellites. More recently the authors have used a CCD receptor mounted on the 1 m telescope of the Pic du Midi Observatory. This new camera has been applied in particular to the observations of differential astrometric measurements of faint satellites near a planet as its performances allow observations of objects with a high contrast. Between 1988 and 1990, 800 satellite-satellite positions of Phobos and Deimos and 900 such...
The prospects for further observations of the intense volcanism on Io discovered during the Voyag... more The prospects for further observations of the intense volcanism on Io discovered during the Voyager 1 mission are discussed. Methods to observe the volcanism and the IR radiation of the associated hot spots are reviewed. The possibility of observing Io during occultations in 1991 is emphasized. The dates for occurrence of occultations predicted by Arlot (1988) and the areas of the earth in which observations should be possible are given.
The study of the rotation of the Earth consists of two parts: the calculation of the precession-n... more The study of the rotation of the Earth consists of two parts: the calculation of the precession-nutation of the Earth in the rigid case, then the determination of complements due to the geophysical components of the Earth. The SMART97 solution (Bretagnon et al., 1998) for the rigid Earth ensures an accuracy at the level of 2 microarcseconds for the three Euler angles. From SMART97, non rigid Earth solutions are built by using transfer functions. For the arguments the frequency of which is close of the frequencies of the FCN or the CW, the amplitudes are multiplied by factors which can reach 100 from the amplitude of the rigid Earth solution. In order to obtain a non rigid Earth solution all the terms of which are computed at the level of precision of 1 microarcsecond, the authors have kept in SMART97 all the terms with an amplitude of 0.01 microarcsecond or more.
Several observational methods have been applied in order to detect asteroidal satellites. Some of... more Several observational methods have been applied in order to detect asteroidal satellites. Some of them were rather successful, such as the stellar occultations and mutual eclipse methods. Recently other techniques such as the space imaging, the adaptive optics and the radar imaging inferred a great improvement in the search for these objects. However several limitations appear in the type of data that each of them allow us to access. We propose to apply an astrometric method in order as well to detect new asteroidal satellites as to get complementary data of some already detected objects (mainly their orbital period). This method is founded on the search of the reflex effect of the primary object due to the orbital motion of a possible satellite. Such an astrometric signature, already searched by Monet & Monet (1998), may reach several tens of MAS. Only a spectral analysis could then detect this signal under good conditions of signal/noise ratio and thanks to high quality astrometri...
On June 8 2004 the planet Venus will pass in front of the disk of the Sun. This rare event (no on... more On June 8 2004 the planet Venus will pass in front of the disk of the Sun. This rare event (no one alive today has never seen such a transit) reminds us the story of the measurement of the Solar System and will be emphasized next year. We would like to take benefit of this event to organize a worldwide network of schools high schools and scientific centers to make the timing of the event of June 8. More we would like to help pupils students and general public to understand a scientific procedure needing an international collaboration and to be aware of the powerful tool that is a transit (detection of extra solar planets ...). Our plans are to organize a centralized computation of the Astronomical Unit through Internet thanks to individual timings of the event to provide notes and educational material to participantsto encourage the interest to science and to promote a safe observation of the Sun. Contacts: http://www.eso.org/outreach/eduoff/vt-2004/http://www.imcce.fr/vt2004
The solution SMART97 (Solution du Mouvement de l'Axe de Rotation de la Terre) is an analytica... more The solution SMART97 (Solution du Mouvement de l'Axe de Rotation de la Terre) is an analytical solution of the motion of the axis of rotation of the Earth, resulting from an improvement of the theory presented in Bretagnon et al. (1997). This solution is built with the analytical theories of the motion of the Moon, the Sun and the planets
ABSTRACT Gaia-FUN-SSO (shortly described at https://www.imcce.fr/gaia-fun-sso/ ) is a ground-base... more ABSTRACT Gaia-FUN-SSO (shortly described at https://www.imcce.fr/gaia-fun-sso/ ) is a ground-based network of observatories set up in the framework of the Gaia consortium (DPAC-CU4) for the follow-up of critical Solar System objects to be discovered from space by the Gaia satellite. Its goal is to retrieve from the ground a newly detected object and to complement the astrometry measurements carried out by Gaia to determine its heliocentric orbit. Data from both Gaia and the ground-based network will be sent to the Minor Planet Center, used to determine the orbit and thus to update the database of minor planet orbits, which is subsequently used by Gaia for the identification of moving objects. We are expecting the detection of many asteroids, mainly from the main belt, and also new near-Earth objects (NEO) at low solar elongation. Owing to the specific conditions of Gaia observations, we even expect the detection of objects whose orbit is fully contained within Earth's orbit (called inner-Earth or Atira asteroids). Several training campaigns have already been organized with the network and it is now able to enter in an operating mode when alerts will be triggered. We describe here the expected number of discoveries, the network, its activity, and the data processing of the central node of the network set in place for the operating mode.
An astrometric technique is described for finding and characterizing asteroid satellites. This te... more An astrometric technique is described for finding and characterizing asteroid satellites. This technique has been applied to observations of asteroid 146 Lucina, which suggests that it may have a satellite.
comets.dat is an ASCII file of cometary orbital elements prepared at the "Institut de Mecani... more comets.dat is an ASCII file of cometary orbital elements prepared at the "Institut de Mecanique Celeste et de Calcul des Ephemerides" (related to the Bureau des Longitudes, Paris). The research and computing needed to generate comets.dat are funded by the French Ministry of Education. The data can be freely used, provided that their origin (Bureau des longitudes) and the author (P. Rocher) are properly cited. User feed-back is encouraged. Unless otherwise specified, send comments and bug reports to: E-mail : stc@imcce.fr Fax : (33) 1 46 33 28 34 Postal mail : IMCCE - Observatoire de Paris 77 avenue Denfert Rochereau F-75014 PARIS (1 data file).
A new method of approximation is used to represent the motions of minor planets which allows ephe... more A new method of approximation is used to represent the motions of minor planets which allows ephemerides to be built in a very compact form. A numerical integration fitted to observations is first performed covering 150 years. Then, by frequency analysis, an approximation of the solution is realized. The ephemeris of the heliocentric rectangular coordinates of the planet is given
The accuracy of the rigid Earth solution SMART97 is 2?µ as over the time interval (1968, 2023), a... more The accuracy of the rigid Earth solution SMART97 is 2?µ as over the time interval (1968, 2023), accuracy showed by the comparison with a numerical integration using the positions of the Moon, the Sun, and the planets given by DE403. To obtain a nonrigid Earth solution, we use the transfer function of Mathews et al. (2000) and, to keep the
The new two-dimensional receptors permit to improve astrometric observations. The authors applied... more The new two-dimensional receptors permit to improve astrometric observations. The authors applied two different types of these receptors to the observations of fast moving objects of the Solar System. In a first step they have developed a video system where the signal of an intensified vidicon camera is digitized and processed in an array processor. Results have been obtained with this receptor for observations which need high speed photometric or astrometric differential measurements: appulses or occultations of stars by asteroids, mutual events of the Galilean satellites. More recently the authors have used a CCD receptor mounted on the 1 m telescope of the Pic du Midi Observatory. This new camera has been applied in particular to the observations of differential astrometric measurements of faint satellites near a planet as its performances allow observations of objects with a high contrast. Between 1988 and 1990, 800 satellite-satellite positions of Phobos and Deimos and 900 such...
The prospects for further observations of the intense volcanism on Io discovered during the Voyag... more The prospects for further observations of the intense volcanism on Io discovered during the Voyager 1 mission are discussed. Methods to observe the volcanism and the IR radiation of the associated hot spots are reviewed. The possibility of observing Io during occultations in 1991 is emphasized. The dates for occurrence of occultations predicted by Arlot (1988) and the areas of the earth in which observations should be possible are given.
The study of the rotation of the Earth consists of two parts: the calculation of the precession-n... more The study of the rotation of the Earth consists of two parts: the calculation of the precession-nutation of the Earth in the rigid case, then the determination of complements due to the geophysical components of the Earth. The SMART97 solution (Bretagnon et al., 1998) for the rigid Earth ensures an accuracy at the level of 2 microarcseconds for the three Euler angles. From SMART97, non rigid Earth solutions are built by using transfer functions. For the arguments the frequency of which is close of the frequencies of the FCN or the CW, the amplitudes are multiplied by factors which can reach 100 from the amplitude of the rigid Earth solution. In order to obtain a non rigid Earth solution all the terms of which are computed at the level of precision of 1 microarcsecond, the authors have kept in SMART97 all the terms with an amplitude of 0.01 microarcsecond or more.
Several observational methods have been applied in order to detect asteroidal satellites. Some of... more Several observational methods have been applied in order to detect asteroidal satellites. Some of them were rather successful, such as the stellar occultations and mutual eclipse methods. Recently other techniques such as the space imaging, the adaptive optics and the radar imaging inferred a great improvement in the search for these objects. However several limitations appear in the type of data that each of them allow us to access. We propose to apply an astrometric method in order as well to detect new asteroidal satellites as to get complementary data of some already detected objects (mainly their orbital period). This method is founded on the search of the reflex effect of the primary object due to the orbital motion of a possible satellite. Such an astrometric signature, already searched by Monet & Monet (1998), may reach several tens of MAS. Only a spectral analysis could then detect this signal under good conditions of signal/noise ratio and thanks to high quality astrometri...
On June 8 2004 the planet Venus will pass in front of the disk of the Sun. This rare event (no on... more On June 8 2004 the planet Venus will pass in front of the disk of the Sun. This rare event (no one alive today has never seen such a transit) reminds us the story of the measurement of the Solar System and will be emphasized next year. We would like to take benefit of this event to organize a worldwide network of schools high schools and scientific centers to make the timing of the event of June 8. More we would like to help pupils students and general public to understand a scientific procedure needing an international collaboration and to be aware of the powerful tool that is a transit (detection of extra solar planets ...). Our plans are to organize a centralized computation of the Astronomical Unit through Internet thanks to individual timings of the event to provide notes and educational material to participantsto encourage the interest to science and to promote a safe observation of the Sun. Contacts: http://www.eso.org/outreach/eduoff/vt-2004/http://www.imcce.fr/vt2004
The solution SMART97 (Solution du Mouvement de l'Axe de Rotation de la Terre) is an analytica... more The solution SMART97 (Solution du Mouvement de l'Axe de Rotation de la Terre) is an analytical solution of the motion of the axis of rotation of the Earth, resulting from an improvement of the theory presented in Bretagnon et al. (1997). This solution is built with the analytical theories of the motion of the Moon, the Sun and the planets
ABSTRACT Gaia-FUN-SSO (shortly described at https://www.imcce.fr/gaia-fun-sso/ ) is a ground-base... more ABSTRACT Gaia-FUN-SSO (shortly described at https://www.imcce.fr/gaia-fun-sso/ ) is a ground-based network of observatories set up in the framework of the Gaia consortium (DPAC-CU4) for the follow-up of critical Solar System objects to be discovered from space by the Gaia satellite. Its goal is to retrieve from the ground a newly detected object and to complement the astrometry measurements carried out by Gaia to determine its heliocentric orbit. Data from both Gaia and the ground-based network will be sent to the Minor Planet Center, used to determine the orbit and thus to update the database of minor planet orbits, which is subsequently used by Gaia for the identification of moving objects. We are expecting the detection of many asteroids, mainly from the main belt, and also new near-Earth objects (NEO) at low solar elongation. Owing to the specific conditions of Gaia observations, we even expect the detection of objects whose orbit is fully contained within Earth's orbit (called inner-Earth or Atira asteroids). Several training campaigns have already been organized with the network and it is now able to enter in an operating mode when alerts will be triggered. We describe here the expected number of discoveries, the network, its activity, and the data processing of the central node of the network set in place for the operating mode.
An astrometric technique is described for finding and characterizing asteroid satellites. This te... more An astrometric technique is described for finding and characterizing asteroid satellites. This technique has been applied to observations of asteroid 146 Lucina, which suggests that it may have a satellite.
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