We report on the ESA Leonid campaign in 2002. As in 1999, our team went to Southern Spain for dou... more We report on the ESA Leonid campaign in 2002. As in 1999, our team went to Southern Spain for double station observations around Granada. We mainly performed video observations; two of our cameras were equipped with objective gratings. We operated one video camera on board an airplane. The electric field of the Earth's atmosphere was also measured. This paper describes our setup and gives some very first results.
During the International Polar Year (IPY) in 2007-2009, EISCAT measured space debris at its Svalb... more During the International Polar Year (IPY) in 2007-2009, EISCAT measured space debris at its Svalbard radar (ESR, latitude 78.2 • N), simultaneously with the stan-dard ionospheric measurement. From the 239 000 events which were recorded in 5060 hours only a "Quality Set" (QS) was extracted for further analysis. The QS essen-tially consists of 101 complete 24-hour beam park debris measurements, between 13 Mar 2007 and 10 Feb 2008, and contains about 95 000 events. The data provide a rel-atively dense sampling of the debris environment above ESR in the first year following the Chinese ASAT event, in January 2007. The QS is freely available in the web.
During the final reentry phase of the Salyut-7 orbital complex, transmissions of radar data were ... more During the final reentry phase of the Salyut-7 orbital complex, transmissions of radar data were received weekly (in January) and daily (last seven days). The radar data comprised measurements of slant range, range rate, azimuth, and elevation. The data were processed by an iterative least squares algorithm to derive the state vector and the ballistic coefficient of the space station. The algorithm is explained, and critical areas where straightforward convergence is hampered are highlighted. Methods to solve the problem of convergence are presented together with the solutions of the orbit determination.
ABSTRACT Chapter 5 outlined the consequences of continuing space activities in a businessas-usual... more ABSTRACT Chapter 5 outlined the consequences of continuing space activities in a businessas-usual fashion, with the conclusion that a timely change of operational practices is required in order to maintain a stable space debris environment, which will permit safe space operations in the long-term future. The main driver for future debris proliferation was found to be the on-orbit mass reservoir, predominantly of LEO objects beyond 100 kg, and potential large-size colliders (mission-related, or due to on-orbit explosions), capable of producing catastrophic break-ups. These break-ups may lead to enhanced feedback collisions and to the onset of a selfsustained runaway situation due to collisional cascading. In the current chapter debris mitigation measures will be identified that can effectively tackle the main causes of an uncontrolled population growth.
In this paper it is derived that the libration of Mercury can be described by γ=Φ0sinM+Φ0/Ksin2M ... more In this paper it is derived that the libration of Mercury can be described by γ=Φ0sinM+Φ0/Ksin2M where Φ0 is the unknown libration amplitude, M is Mercury's mean anomaly and K=−9.483. Φ0 can be determined by comparing pairs of images of the same landmarks taken by an orbiter at different positions of Mercury. If the angle between the orbit plane of a polar orbiter and Mercury's line of periapsis is between −60° and 60° and if one landmark at the equator is imaged per day with a relative precision of 1.6arcsec, then the libration amplitude can be determined in two Mercury years (176 days) with an accuracy of 1arcsec or better, which is sufficient to answer the question whether Mercury has a solid or fluid core.
BepiColombo mission shall answer a number of questions about Mercury. Among them: the rotation st... more BepiColombo mission shall answer a number of questions about Mercury. Among them: the rotation state of the planet, the static and dynamic gravitational field. Very precise range and range-rate tracking will be used together with on-board accelerometer data and the observation of landmarks on the surface of Mercury. This paper presents the achievable accuracy for the gravitational field coefficients up
BepiColombo, an ESA science mission, will reach Mercury in early 2017. The complex nearly 5-year ... more BepiColombo, an ESA science mission, will reach Mercury in early 2017. The complex nearly 5-year long transfer consists of 6 flybys and many extended thrust arcs where the spacecraft is accelerated by solar electric propulsion. The thrust level is too low for a capture from a hyperbolic approach. To avoid a single point failure of a classical chemical orbit insertion
We report on the ESA Leonid campaign in 2002. As in 1999, our team went to Southern Spain for dou... more We report on the ESA Leonid campaign in 2002. As in 1999, our team went to Southern Spain for double station observations around Granada. We mainly performed video observations; two of our cameras were equipped with objective gratings. We operated one video camera on board an airplane. The electric field of the Earth's atmosphere was also measured. This paper describes our setup and gives some very first results.
During the International Polar Year (IPY) in 2007-2009, EISCAT measured space debris at its Svalb... more During the International Polar Year (IPY) in 2007-2009, EISCAT measured space debris at its Svalbard radar (ESR, latitude 78.2 • N), simultaneously with the stan-dard ionospheric measurement. From the 239 000 events which were recorded in 5060 hours only a "Quality Set" (QS) was extracted for further analysis. The QS essen-tially consists of 101 complete 24-hour beam park debris measurements, between 13 Mar 2007 and 10 Feb 2008, and contains about 95 000 events. The data provide a rel-atively dense sampling of the debris environment above ESR in the first year following the Chinese ASAT event, in January 2007. The QS is freely available in the web.
During the final reentry phase of the Salyut-7 orbital complex, transmissions of radar data were ... more During the final reentry phase of the Salyut-7 orbital complex, transmissions of radar data were received weekly (in January) and daily (last seven days). The radar data comprised measurements of slant range, range rate, azimuth, and elevation. The data were processed by an iterative least squares algorithm to derive the state vector and the ballistic coefficient of the space station. The algorithm is explained, and critical areas where straightforward convergence is hampered are highlighted. Methods to solve the problem of convergence are presented together with the solutions of the orbit determination.
ABSTRACT Chapter 5 outlined the consequences of continuing space activities in a businessas-usual... more ABSTRACT Chapter 5 outlined the consequences of continuing space activities in a businessas-usual fashion, with the conclusion that a timely change of operational practices is required in order to maintain a stable space debris environment, which will permit safe space operations in the long-term future. The main driver for future debris proliferation was found to be the on-orbit mass reservoir, predominantly of LEO objects beyond 100 kg, and potential large-size colliders (mission-related, or due to on-orbit explosions), capable of producing catastrophic break-ups. These break-ups may lead to enhanced feedback collisions and to the onset of a selfsustained runaway situation due to collisional cascading. In the current chapter debris mitigation measures will be identified that can effectively tackle the main causes of an uncontrolled population growth.
In this paper it is derived that the libration of Mercury can be described by γ=Φ0sinM+Φ0/Ksin2M ... more In this paper it is derived that the libration of Mercury can be described by γ=Φ0sinM+Φ0/Ksin2M where Φ0 is the unknown libration amplitude, M is Mercury's mean anomaly and K=−9.483. Φ0 can be determined by comparing pairs of images of the same landmarks taken by an orbiter at different positions of Mercury. If the angle between the orbit plane of a polar orbiter and Mercury's line of periapsis is between −60° and 60° and if one landmark at the equator is imaged per day with a relative precision of 1.6arcsec, then the libration amplitude can be determined in two Mercury years (176 days) with an accuracy of 1arcsec or better, which is sufficient to answer the question whether Mercury has a solid or fluid core.
BepiColombo mission shall answer a number of questions about Mercury. Among them: the rotation st... more BepiColombo mission shall answer a number of questions about Mercury. Among them: the rotation state of the planet, the static and dynamic gravitational field. Very precise range and range-rate tracking will be used together with on-board accelerometer data and the observation of landmarks on the surface of Mercury. This paper presents the achievable accuracy for the gravitational field coefficients up
BepiColombo, an ESA science mission, will reach Mercury in early 2017. The complex nearly 5-year ... more BepiColombo, an ESA science mission, will reach Mercury in early 2017. The complex nearly 5-year long transfer consists of 6 flybys and many extended thrust arcs where the spacecraft is accelerated by solar electric propulsion. The thrust level is too low for a capture from a hyperbolic approach. To avoid a single point failure of a classical chemical orbit insertion
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Papers by R. Jehn