Mark Vincent | RAYTHEON - Academia.edu (original) (raw)

Papers by Mark Vincent

PixelLearn is an integrated user-interface computer program for classifying pixels in scientific ... more PixelLearn is an integrated user-interface computer program for classifying pixels in scientific images. Heretofore, training a machine-learning algorithm to classify pixels in images has been tedious and difficult. PixelLearn provides a graphical user interface that makes it faster and more intuitive, leading to more interactive exploration of image data sets. PixelLearn also provides image-enhancement controls to make it easier to see subtle details in images. PixelLearn opens images or sets of images in a variety of common scientific file formats and enables the user to interact with several supervised or unsupervised machine-learning pixel-classifying algorithms while the user continues to browse through the images. The machinelearning algorithms in PixelLearn use advanced clustering and classification methods that enable accuracy much higher than is achievable by most other software previously available for this purpose. Pixel-Learn is written in portable C++ and runs natively on computers running Linux, Windows, or Mac OS X.

Frozen orbits are orbits which have only short-period changes in their mean eccentricity and argu... more Frozen orbits are orbits which have only short-period changes in their mean eccentricity and argument of periapse, so that they basically keep a fixed orientation within their plane of motion. Nearly frozen orbits are those whose eccentricity and argument of periapse have values close to those of a frozen orbit. We call them "nearly" frozen because their eccentricity vector (a vector whose polar coordinates are eccentricity and argument of periapse) will stay within a bounded distance from the frozen orbit eccentricity vector, circulating around it over time. For highly inclined orbits around the Earth, this distance is effectively constant over time. Furthermore, frozen orbit eccentricity values are low enough that these orbits are essentially eccentric (i.e., off center) circles, so that nearly frozen orbits around Earth are bounded above and below by frozen orbits.

The NISAR mission is a proposed joint mission of the space agencies of India and the United State... more The NISAR mission is a proposed joint mission of the space agencies of India and the United States. It would use L-band SAR radar interferometry to measure very small changes in the topography of the Earth including ice sheets. The use of interferometry places more stringent requirements on the orbit design and maintenance of this mission than any earlier robotic mission in either agency has had to meet. This paper discusses how the requirements led to the orbit design and outlines orbit maintenance strategies to meet the orbit requirements.

Frozen orbits are orbits which have only short-period changes in their mean eccentricity and argu... more Frozen orbits are orbits which have only short-period changes in their mean eccentricity and argument of periapse, so that they basically keep a fixed orientation within their plane of motion. Nearly frozen orbits are those whose eccentricity and argument of periapse have values close to those of a frozen orbit. We call them "nearly" frozen because their eccentricity vector (a vector whose polar coordinates are eccentricity and argument of periapse) will stay within a bounded distance from the frozen orbit eccentricity vector, circulating around it over time. For highly inclined orbits around the Earth, this distance is effectively constant over time. Furthermore, frozen orbit eccentricity values are low enough that these orbits are essentially eccentric (i.e., off center) circles, so that nearly frozen orbits around Earth are bounded above and below by frozen orbits.

The currently preferred design for a global topography satellite mission poses a challenging task... more The currently preferred design for a global topography satellite mission poses a challenging task in orbit design and navigation since it requires close formation flying of two radar antenna equipped satellites. This paper describes the origin of the orbital requirements and some methods to achieve success. Preliminary analysis indicates that the mission is technically sound but would require precise navigation and intensive mission opcrat ions. lNTROT)lJCI'10N Although the topographies of cer(ain small areas of the Earth's land masses are well known, there is a need for a high resolution global map. Vertical accuracy of 5 meter or bet ter, on a horizontal grid of 30 m would be a useful product to a number of customers. This paper presents the interesting astrodynamics involved with a dual satellite mission concept which was the leading candidate chosen out of an intensive study of so-called '1'OPSAT missions carried out at JPI., The basic mission would provide the required data for all the land masses between f 70° ]atitude. The recently proven InSAR (Interfcrometric Synthetic Aperture Radar) method would be used to obtain the aeeuracy needed. MISSION CONCEPTS 'J'hree different methods of obtaining the lnSAR images were considered. The * Tk rcsc,arch dcscribcd in this paper was carried out by the JCL Propulsion 1,aboratory, California lnstiwc of Technology, under contract with National Acmnautics and Space, Adn)inistmtion. Prepared for technical papers that may Iatcr k published in the proceedings of the Arncrican As(ronaatical SOcicty.

Celestial mechanics, May 1, 1986

The relativistic equations of motion are derived for N self-gravitating, rotating finite bodies. ... more The relativistic equations of motion are derived for N self-gravitating, rotating finite bodies. These equations are then applied to the near-Earth satellite orbit determination problem. The apparent change of the shape of the Earth from the Earth centered frame to the Solar System barycentric frame changes the value of the Newtonian potential term in the metric. This in turn leads to a simplification of the equations of motion in the barycentric frame.

Journal of Geophysical Research, 1990

Covariance studies were performed to investigate the orbit determination problem for a small tran... more Covariance studies were performed to investigate the orbit determination problem for a small transponder satellite in a nearly circular polar orbit with 4-hour period around Mercury. With X band and Ka band Doppler and range measurements, the analysis indicates that the gravitational field through degree and order 10 can be solved for from as few as 40 separate 8-hour arcs of tracking data. In addition, the Earth-Mercury distance can be determined during each ranging period with about 6-cm accuracy. The expected geoid accuracy is 10 cm up through degree 5, and 1 m through degree 8. The main error sources were the geocentric range measurement error, the uncertainties in higher degree gravity field terms, which were not solved for, and the solar radiation pressure uncertainty.

AIAA/AAS Astrodynamics Specialist Conference and Exhibit, Jun 15, 2008

In order to gain an understanding into the problem of eccentricity (e) and argument of perigee (o... more In order to gain an understanding into the problem of eccentricity (e) and argument of perigee (omega) control for TOPEX/Poseidon, the two cases where the highest latitude crossing time and one of the equator crossings are held constant are investigated. Variations in e and omega cause a significant effect on the satellite's ground-track repeatability. Maintaining e and omega near their frozen values will minimize this variation. Analytical expressions are found to express this relationship while keeping an arbitrary point of the ground track fixed. The initial offset of the ground track from its nominal path determines the subsequent evolution of e and omega about their frozen values. This long-term behavior is numerically determined using an earth gravitational field including the first 17 zonal harmonics. The numerical results are plotted together with the analytical constraints to see if the later values of e and omega cause unacceptable deviation in the ground track.

Astrodynamics Conference, Aug 17, 1990

Mean Orbit Elements can be chosen such that a desired ground track repeat criteria is obtained wh... more Mean Orbit Elements can be chosen such that a desired ground track repeat criteria is obtained when propagating with the secular effects of a central body gravity field. If the proper initial conditions are chosen that correspond to these Mean Elements, the orbit can also be propagated with the full gravity field and form another ground track repeat pattern. Further, if the effects of other perturbative forces are compensated for, such that the ground track remains near this pattern, the central body effects can again be considered repetitive. The process of arriving at these conclusions, along with the supporting numerical simulations, are presented.

The accuracy of solar system tests of gravitational theory could be very much improved by range a... more The accuracy of solar system tests of gravitational theory could be very much improved by range and Doppler measurements to a Small Mercury Relativity Orbiter. A nearly circular orbit at roughly 2400 km altitude is assumed in order to minimize problems with orbit determination and thermal radiation from the surface. The spacecraft is spin-stabilized and has a 30 cm diameter de-spun antenna. With K-band and X-band ranging systems using a 50 MHz offset sidetone at K-band, a range accuracy of 3 cm appears to be realistically achievable. The estimated spacecraft mass is 50 kg. A consider-covariance analysis was performed to determine how well the Earth-Mercury distance as a function of time could be determined with such a Relativity Orbiter. The minimum data set is assumed to be 40 independent 8-hour arcs of tracking data at selected times during a two year period. The gravity field of Mercury up through degree and order 10 is solved for, along with the initial conditions for each arc and the Earth-Mercury distance at the center of each arc. The considered parameters include the gravity field parameters of degree 11 and 12 plus the tracking station coordinates, the tropospheric delay, and two parameters in a crude radiation pressure model. The conclusion is that the Earth-Mercury distance can be determined to 6 cm accuracy or better. From a modified worst-case analysis, this would lead to roughly 2 orders of magnitude improvement in the knowledge of the precession of perihelion, the relativistic time delay, and the possible change in the gravitational constant with time.

The method and terms used to design the target parameters that will be used to insert the Orbitin... more The method and terms used to design the target parameters that will be used to insert the Orbiting Carbon Observatory 2 (OCO-2) into the A-train are defined. Comparisons are made to the plan that would have been used had OCO-1 successfully achieved its Injection Orbit. Major differences arise from the fact that OCO-1 was launched on a Taurus XL with a target 65 km below the A-Train while OCO-2 will be launched on a Delta II with a target only 15 km below the A-Train. The new plan is similar to the one used for the CloudSat/CALIPSO missions, but reformulated into a one-step iteration process that is easier to understand.

amos, Sep 1, 2016

A computer program named PC4 has been created to produce the confidence levels that future Probab... more A computer program named PC4 has been created to produce the confidence levels that future Probability of Collision (Pc) will not exceed chosen thresholds. Its results compared favorably to those from an earlier spreadsheet version using the same algorithms. Insights into the bounding values of both current and future Pc values were obtained. The need for state covariance scaling and improved modeling of solar activity/atmospheric density is presented. The recommended post-maneuver thresholds for maneuver planning are also presented.

Proceedings of SPIE, Oct 23, 2012

The scientific benefits generated from the synergy of the satellites in the AM and PM (A-Train) C... more The scientific benefits generated from the synergy of the satellites in the AM and PM (A-Train) Constellations are unprecedented. Constellation Flying in this context refers to each satellite flying independently in their own control box with acceptable minimum buffers ensuring that the control boxes do not intersect each other. Recently it is has been realized that rather than two separate constellations, they should be considered as one entity called the “705-km Fleet” named for their common nominal altitude over the equator. This realization partly comes from the recent events with the USGS satellite Landsat-5 which is in the AM Constellation, but for a period of time was overlapping with the A-Train. A fundamental concept is the Triad consisting of Alongtrack Phasing, Groundtrack and Mean Local Time of Ascending Node. Another related lesson learned is that to maintain the buffers, phasing at the two intersection points where each pair of orbits cross near the poles should be considered, as opposed to the relative phasing of the times they cross the equator. These types of geometric considerations are presented after presenting an introduction and history of the constellations. Other topics include: reference ground tracks, the process of handling the growing concern of conjunctions with other orbiting bodies, CloudSat and CALIPSO satellites performing Formation Flying, and the general ascent and exit methods for satellites entering/leaving a constellation.

Advances in Space Research, 1989

Abstract It was shown earlier that 1× 10− 14 Doppler data and 3 cm accuracy range measurements to... more Abstract It was shown earlier that 1× 10− 14 Doppler data and 3 cm accuracy range measurements to a small Mercury Relativity Satellite in a polar orbit with 4-hour period can give high-accuracy tests of gravitational theory. A particular conceptual design has been ...

The collaborative science obtained from the satellites in the A-Train is an unparalleled success.... more The collaborative science obtained from the satellites in the A-Train is an unparalleled success. The constellation framework that has evolved is well-formulated and documented by its international members. Communication between teams is enhanced by a web-based Constellation Coordination System. Safety and correlated observations are ensured by defining independent control boxes with buffers in between. Each mission stays within its control box by regular drag makeup maneuvers. Annual inclination adjustments are coordinated by all missions to maintain their absolute and relative Mean Local Time of Ascending Node (MLTAN). Since the satellites are in different orbit planes their separation involves a three-dimensional triad made up of the alongtrack separations, reference groundtracks and MLTAN's. For further safety, a Constellation Envelope has been defined to determine safe entry and exit orbits.

Designs for a laser gravitational wave antenna in space using free test masses and heterodyne (in... more Designs for a laser gravitational wave antenna in space using free test masses and heterodyne (interferometric) detection were investigated. Use of 1 million km baselines between three spacecraft in nearly circular 1 yr solar orbit is considered. With milliwatt-transmitted laser power ...

Advances in Space Research, 1989

Progress during the past two years on a proposed Laser Gravitational-Wave Observatory in Space (L... more Progress during the past two years on a proposed Laser Gravitational-Wave Observatory in Space (LAGOS) is discussed. Calculated performance for a 10 6 km sized antenna over the frequency range of 10 −5 to 1 Hz is given. The sensitivity from 10 −3 to 10 −1 Hz is expected to be 1 ...

PixelLearn is an integrated user-interface computer program for classifying pixels in scientific ... more PixelLearn is an integrated user-interface computer program for classifying pixels in scientific images. Heretofore, training a machine-learning algorithm to classify pixels in images has been tedious and difficult. PixelLearn provides a graphical user interface that makes it faster and more intuitive, leading to more interactive exploration of image data sets. PixelLearn also provides image-enhancement controls to make it easier to see subtle details in images. PixelLearn opens images or sets of images in a variety of common scientific file formats and enables the user to interact with several supervised or unsupervised machine-learning pixel-classifying algorithms while the user continues to browse through the images. The machinelearning algorithms in PixelLearn use advanced clustering and classification methods that enable accuracy much higher than is achievable by most other software previously available for this purpose. Pixel-Learn is written in portable C++ and runs natively on computers running Linux, Windows, or Mac OS X.

Frozen orbits are orbits which have only short-period changes in their mean eccentricity and argu... more Frozen orbits are orbits which have only short-period changes in their mean eccentricity and argument of periapse, so that they basically keep a fixed orientation within their plane of motion. Nearly frozen orbits are those whose eccentricity and argument of periapse have values close to those of a frozen orbit. We call them "nearly" frozen because their eccentricity vector (a vector whose polar coordinates are eccentricity and argument of periapse) will stay within a bounded distance from the frozen orbit eccentricity vector, circulating around it over time. For highly inclined orbits around the Earth, this distance is effectively constant over time. Furthermore, frozen orbit eccentricity values are low enough that these orbits are essentially eccentric (i.e., off center) circles, so that nearly frozen orbits around Earth are bounded above and below by frozen orbits.

The NISAR mission is a proposed joint mission of the space agencies of India and the United State... more The NISAR mission is a proposed joint mission of the space agencies of India and the United States. It would use L-band SAR radar interferometry to measure very small changes in the topography of the Earth including ice sheets. The use of interferometry places more stringent requirements on the orbit design and maintenance of this mission than any earlier robotic mission in either agency has had to meet. This paper discusses how the requirements led to the orbit design and outlines orbit maintenance strategies to meet the orbit requirements.

Frozen orbits are orbits which have only short-period changes in their mean eccentricity and argu... more Frozen orbits are orbits which have only short-period changes in their mean eccentricity and argument of periapse, so that they basically keep a fixed orientation within their plane of motion. Nearly frozen orbits are those whose eccentricity and argument of periapse have values close to those of a frozen orbit. We call them "nearly" frozen because their eccentricity vector (a vector whose polar coordinates are eccentricity and argument of periapse) will stay within a bounded distance from the frozen orbit eccentricity vector, circulating around it over time. For highly inclined orbits around the Earth, this distance is effectively constant over time. Furthermore, frozen orbit eccentricity values are low enough that these orbits are essentially eccentric (i.e., off center) circles, so that nearly frozen orbits around Earth are bounded above and below by frozen orbits.

The currently preferred design for a global topography satellite mission poses a challenging task... more The currently preferred design for a global topography satellite mission poses a challenging task in orbit design and navigation since it requires close formation flying of two radar antenna equipped satellites. This paper describes the origin of the orbital requirements and some methods to achieve success. Preliminary analysis indicates that the mission is technically sound but would require precise navigation and intensive mission opcrat ions. lNTROT)lJCI'10N Although the topographies of cer(ain small areas of the Earth's land masses are well known, there is a need for a high resolution global map. Vertical accuracy of 5 meter or bet ter, on a horizontal grid of 30 m would be a useful product to a number of customers. This paper presents the interesting astrodynamics involved with a dual satellite mission concept which was the leading candidate chosen out of an intensive study of so-called '1'OPSAT missions carried out at JPI., The basic mission would provide the required data for all the land masses between f 70° ]atitude. The recently proven InSAR (Interfcrometric Synthetic Aperture Radar) method would be used to obtain the aeeuracy needed. MISSION CONCEPTS 'J'hree different methods of obtaining the lnSAR images were considered. The * Tk rcsc,arch dcscribcd in this paper was carried out by the JCL Propulsion 1,aboratory, California lnstiwc of Technology, under contract with National Acmnautics and Space, Adn)inistmtion. Prepared for technical papers that may Iatcr k published in the proceedings of the Arncrican As(ronaatical SOcicty.

Celestial mechanics, May 1, 1986

The relativistic equations of motion are derived for N self-gravitating, rotating finite bodies. ... more The relativistic equations of motion are derived for N self-gravitating, rotating finite bodies. These equations are then applied to the near-Earth satellite orbit determination problem. The apparent change of the shape of the Earth from the Earth centered frame to the Solar System barycentric frame changes the value of the Newtonian potential term in the metric. This in turn leads to a simplification of the equations of motion in the barycentric frame.

Journal of Geophysical Research, 1990

Covariance studies were performed to investigate the orbit determination problem for a small tran... more Covariance studies were performed to investigate the orbit determination problem for a small transponder satellite in a nearly circular polar orbit with 4-hour period around Mercury. With X band and Ka band Doppler and range measurements, the analysis indicates that the gravitational field through degree and order 10 can be solved for from as few as 40 separate 8-hour arcs of tracking data. In addition, the Earth-Mercury distance can be determined during each ranging period with about 6-cm accuracy. The expected geoid accuracy is 10 cm up through degree 5, and 1 m through degree 8. The main error sources were the geocentric range measurement error, the uncertainties in higher degree gravity field terms, which were not solved for, and the solar radiation pressure uncertainty.

AIAA/AAS Astrodynamics Specialist Conference and Exhibit, Jun 15, 2008

In order to gain an understanding into the problem of eccentricity (e) and argument of perigee (o... more In order to gain an understanding into the problem of eccentricity (e) and argument of perigee (omega) control for TOPEX/Poseidon, the two cases where the highest latitude crossing time and one of the equator crossings are held constant are investigated. Variations in e and omega cause a significant effect on the satellite's ground-track repeatability. Maintaining e and omega near their frozen values will minimize this variation. Analytical expressions are found to express this relationship while keeping an arbitrary point of the ground track fixed. The initial offset of the ground track from its nominal path determines the subsequent evolution of e and omega about their frozen values. This long-term behavior is numerically determined using an earth gravitational field including the first 17 zonal harmonics. The numerical results are plotted together with the analytical constraints to see if the later values of e and omega cause unacceptable deviation in the ground track.

Astrodynamics Conference, Aug 17, 1990

Mean Orbit Elements can be chosen such that a desired ground track repeat criteria is obtained wh... more Mean Orbit Elements can be chosen such that a desired ground track repeat criteria is obtained when propagating with the secular effects of a central body gravity field. If the proper initial conditions are chosen that correspond to these Mean Elements, the orbit can also be propagated with the full gravity field and form another ground track repeat pattern. Further, if the effects of other perturbative forces are compensated for, such that the ground track remains near this pattern, the central body effects can again be considered repetitive. The process of arriving at these conclusions, along with the supporting numerical simulations, are presented.

The accuracy of solar system tests of gravitational theory could be very much improved by range a... more The accuracy of solar system tests of gravitational theory could be very much improved by range and Doppler measurements to a Small Mercury Relativity Orbiter. A nearly circular orbit at roughly 2400 km altitude is assumed in order to minimize problems with orbit determination and thermal radiation from the surface. The spacecraft is spin-stabilized and has a 30 cm diameter de-spun antenna. With K-band and X-band ranging systems using a 50 MHz offset sidetone at K-band, a range accuracy of 3 cm appears to be realistically achievable. The estimated spacecraft mass is 50 kg. A consider-covariance analysis was performed to determine how well the Earth-Mercury distance as a function of time could be determined with such a Relativity Orbiter. The minimum data set is assumed to be 40 independent 8-hour arcs of tracking data at selected times during a two year period. The gravity field of Mercury up through degree and order 10 is solved for, along with the initial conditions for each arc and the Earth-Mercury distance at the center of each arc. The considered parameters include the gravity field parameters of degree 11 and 12 plus the tracking station coordinates, the tropospheric delay, and two parameters in a crude radiation pressure model. The conclusion is that the Earth-Mercury distance can be determined to 6 cm accuracy or better. From a modified worst-case analysis, this would lead to roughly 2 orders of magnitude improvement in the knowledge of the precession of perihelion, the relativistic time delay, and the possible change in the gravitational constant with time.

The method and terms used to design the target parameters that will be used to insert the Orbitin... more The method and terms used to design the target parameters that will be used to insert the Orbiting Carbon Observatory 2 (OCO-2) into the A-train are defined. Comparisons are made to the plan that would have been used had OCO-1 successfully achieved its Injection Orbit. Major differences arise from the fact that OCO-1 was launched on a Taurus XL with a target 65 km below the A-Train while OCO-2 will be launched on a Delta II with a target only 15 km below the A-Train. The new plan is similar to the one used for the CloudSat/CALIPSO missions, but reformulated into a one-step iteration process that is easier to understand.

amos, Sep 1, 2016

A computer program named PC4 has been created to produce the confidence levels that future Probab... more A computer program named PC4 has been created to produce the confidence levels that future Probability of Collision (Pc) will not exceed chosen thresholds. Its results compared favorably to those from an earlier spreadsheet version using the same algorithms. Insights into the bounding values of both current and future Pc values were obtained. The need for state covariance scaling and improved modeling of solar activity/atmospheric density is presented. The recommended post-maneuver thresholds for maneuver planning are also presented.

Proceedings of SPIE, Oct 23, 2012

The scientific benefits generated from the synergy of the satellites in the AM and PM (A-Train) C... more The scientific benefits generated from the synergy of the satellites in the AM and PM (A-Train) Constellations are unprecedented. Constellation Flying in this context refers to each satellite flying independently in their own control box with acceptable minimum buffers ensuring that the control boxes do not intersect each other. Recently it is has been realized that rather than two separate constellations, they should be considered as one entity called the “705-km Fleet” named for their common nominal altitude over the equator. This realization partly comes from the recent events with the USGS satellite Landsat-5 which is in the AM Constellation, but for a period of time was overlapping with the A-Train. A fundamental concept is the Triad consisting of Alongtrack Phasing, Groundtrack and Mean Local Time of Ascending Node. Another related lesson learned is that to maintain the buffers, phasing at the two intersection points where each pair of orbits cross near the poles should be considered, as opposed to the relative phasing of the times they cross the equator. These types of geometric considerations are presented after presenting an introduction and history of the constellations. Other topics include: reference ground tracks, the process of handling the growing concern of conjunctions with other orbiting bodies, CloudSat and CALIPSO satellites performing Formation Flying, and the general ascent and exit methods for satellites entering/leaving a constellation.

Advances in Space Research, 1989

Abstract It was shown earlier that 1× 10− 14 Doppler data and 3 cm accuracy range measurements to... more Abstract It was shown earlier that 1× 10− 14 Doppler data and 3 cm accuracy range measurements to a small Mercury Relativity Satellite in a polar orbit with 4-hour period can give high-accuracy tests of gravitational theory. A particular conceptual design has been ...

The collaborative science obtained from the satellites in the A-Train is an unparalleled success.... more The collaborative science obtained from the satellites in the A-Train is an unparalleled success. The constellation framework that has evolved is well-formulated and documented by its international members. Communication between teams is enhanced by a web-based Constellation Coordination System. Safety and correlated observations are ensured by defining independent control boxes with buffers in between. Each mission stays within its control box by regular drag makeup maneuvers. Annual inclination adjustments are coordinated by all missions to maintain their absolute and relative Mean Local Time of Ascending Node (MLTAN). Since the satellites are in different orbit planes their separation involves a three-dimensional triad made up of the alongtrack separations, reference groundtracks and MLTAN's. For further safety, a Constellation Envelope has been defined to determine safe entry and exit orbits.

Designs for a laser gravitational wave antenna in space using free test masses and heterodyne (in... more Designs for a laser gravitational wave antenna in space using free test masses and heterodyne (interferometric) detection were investigated. Use of 1 million km baselines between three spacecraft in nearly circular 1 yr solar orbit is considered. With milliwatt-transmitted laser power ...

Advances in Space Research, 1989

Progress during the past two years on a proposed Laser Gravitational-Wave Observatory in Space (L... more Progress during the past two years on a proposed Laser Gravitational-Wave Observatory in Space (LAGOS) is discussed. Calculated performance for a 10 6 km sized antenna over the frequency range of 10 −5 to 1 Hz is given. The sensitivity from 10 −3 to 10 −1 Hz is expected to be 1 ...