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Papers by juan carlos dolado perez
Acta Astronautica, 2021
Abstract This paper describes a process for identifying the intact objects in orbit that (a) pose... more Abstract This paper describes a process for identifying the intact objects in orbit that (a) pose the greatest debris-generating potential risk to operational satellites or (b) would reduce the risk the most if they were removed or prevented from colliding with each other (i.e., remediated). To accomplish this, a number of diverse, international space organizations were solicited to contribute their lists of the 50 statistically-most-concerning objects. The results of the multiple algorithms are compared, a composite ranked list is provided, and the significance of the consolidated list is presented including critical assumptions and key factors in determining this “hit list.” It is found that the four primary factors used in these processes are mass, encounter rates, orbital lifetime, and proximity to operational satellites. This cooperative international assessment provides a useful ranking of the most hazardous massive derelicts in low Earth orbit as a prioritized list for remediation to (1) enhance space safety and (2) assure long-term space sustainability. This will hopefully catalyze international action in debris remediation.
Objects in Low-Earth Orbits (LEO) and Highly Elliptical Orbits (HEO) are subject to decay and re-... more Objects in Low-Earth Orbits (LEO) and Highly Elliptical Orbits (HEO) are subject to decay and re-entry into the atmosphere due mainly to the drag force. While being this process the best solution to avoid the proliferation of debris in space and to ensure the future sustainability of space activities, it implies a certain amount of risk as many of these reentries are done in an uncontrolled manner. In order to have a better insight on the objects reentering the Earth’s atmosphere, in short and middle term, and on the risk posed by these re-entries, CNES has developed a tool named OPERA (Outil de PrEvision des dates des Rentrées Atmosphèriques non contrôlées). This paper will concentrate on the prediction of the in-orbit lifetime of a space object, based on publicly available TLE (Two Line Elements sets) data, as it has been implemented in OPERA. To this purpose, several operations are needed prior to the computation of the residual in-orbit lifetime of such object, by the propagatio...
Since the launch of Sputnik-I in 1957, the amount of space debris in Earth׳s orbit has increased ... more Since the launch of Sputnik-I in 1957, the amount of space debris in Earth׳s orbit has increased continuously. Historically, besides abandoned intact objects (spacecraft and orbital stages), the primary sources of space debris in Earth׳s orbit were (i) accidental and intentional break-ups which produced long-lasting debris and (ii) debris released intentionally during the operation of launch vehicle orbital stages and spacecraft. In the future, fragments generated by collisions are expected to become a significant source as well.
In this context, and from a purely mathematical point of view, the orbital debris population in Low Earth Orbit (LEO) should be intrinsically unstable, due to the physics of mutual collisions and the relative ineffectiveness of natural sink mechanisms above~700 km. Therefore, the real question should not be “if”, but “when” the exponential growth of the space debris population is supposed to start. From a practical point of view, and in order to answer the previous question, since the end of the 1980׳s several sophisticated long-term debris evolutionary models have been developed.
Unfortunately, the predictions performed with such models, in particular beyond a few decades, are affected by considerable uncertainty. Such uncertainty comes from a relative important number of variables that being either under the partial control or completely out of the control of modellers, introduce a variability on the long-term simulation of the space debris population which cannot be captured with standard Monte Carlo statistics.
The objective of this paper is to present and discuss many of the uncertainty sources affecting the long-term predictions done with evolutionary models, in order to serve as a roadmap for the uncertainty and the statistical robustness analysis of the long-term evolution of the space debris population.
Since 1994, where COPUOS considered for the first time, on a priority basis, matters associated w... more Since 1994, where COPUOS considered for the first time, on a priority basis, matters associated with space debris, many countries and international organization have agreed, via the publication of space debris mitigation guidelines, on the need to mitigate the risk posed by the space debris environment. At international level, the Inter Agencies space Debris Committee (IADC) published its mitigation guidelines in 2002 and COPUOS adopted its space debris mitigation guidelines in 2007. In France, the French Space Operations Act (FSOA), which also deals with this problematic, came into force in 2010.
The work presented on this paper aims to investigate the global compliance of mitigation guidelines by space operators over a 13 years period (2000 – 2012). We are particularly interested in studying the expected decrease of the mid or long term risk in LEO, through the application of the 25 year rule or the re-orbitation above the LEO graveyard orbit.
First of all we have gathered orbital information, mainly from publicly available sources, of satellites and launcher elements crossing or near the LEO protected region (defined by an altitude lower than 2000 Km). From the previous sub-set of space objects, we have identified those arriving to end of mission between 2000 and 2012 by detecting the last orbital maneuver. This has been possible by the development of maneuver detection algorithms, which from the analysis of temporal series of orbital data are able to compute the manoeuvres dates and magnitude.
For the space objects arriving to end of mission between 2000 and 2012 that have not decayed yet, the knowledge of their physical characteristics as the ballistic coefficient, is necessary to estimate a re-entry duration. In order to obtain such information, specific algorithms have been developed and validated in the frame of this study.
Finally, the orbital lifetime of each space object has been computed under the standard methods defined in the framework of the FSOA for what concerns solar activity prediction.
One of the main results of our study consists in the rate of compliance of LEO mitigation guidelines for each year between 2000 and 2012, for spacecrafts as well as for launcher elements. This allows us to analyze the existence of trends showing the improvement of the mitigation guidelines compliance over the years.
Objects in Low-Earth Orbits (LEO) and Highly Elliptical Orbits (HEO) are subject to decay and re-... more Objects in Low-Earth Orbits (LEO) and Highly Elliptical Orbits (HEO) are subject to decay and re-entry into the atmosphere due mainly to the drag force. While being this process the best solution to avoid the proliferation of debris in space and to ensure the future sustainability of space activities, it implies a certain amount of risk as many of these reentries are done in an uncontrolled manner.
In order to have a better insight on the objects reentering the Earth’s atmosphere, in short and middle term, and on the risk posed by these re-entries, CNES has developed a tool named OPERA (Outil de PrEvision des dates des Rentrées Atmosphèriques non contrôlées).
This paper will concentrate on the prediction of the in-orbit lifetime of a space object, based on publicly available TLE (Two Line Elements sets) data, as it has been implemented in OPERA.
To this purpose, several operations are needed prior to the computation of the residual in-orbit lifetime of such object, by the propagation of its orbital position up to re-entry.
These operations include the pre-processing of the TLE data by filtering their outliers and detecting maneuvers, as only non-maneuverable objects are considered for the analysis, the preliminary estimation of objects area-to-mass ratio and the final estimation of the orbits based on a weighted least-squares algorithm taking the TLE states as input pseudo-observations. Additionally, the accuracy (estimation error) of the results obtained for known past reentries will be presented.
With the increase on the number of satellite constellations, multiple encounters become more and ... more With the increase on the number of satellite constellations, multiple encounters become more and more common. In the
event of this type of encounters and in order to compute the overall collision probability, it is necessary to analyse the collision risk of all the encounters as a whole instead of taking them into account separately.
A N encounters collision probability may be computed by Monte Carlo method. Unfortunately, this could be extremely expensive in term of computation. We develop two criteria to avoid as much as possible Monte Carlo trials. The first criterion is based on the bracketing of the real probability by two probabilities that may be computed with individual encounter probabilities. This criterion is useful to probe the collision probability magnitude. In many cases, we observe that up to some security threshold, the N encounters collision probability is equal to the summation of the individual collision probability.
We develop a geometrical criterion to predict the threshold domain where we can compute the N encounters collision probability through an addition of individual collision probability.
In this paper, we expose the method to compute the two criteria, there meaning and illustrate their use on some cases of multiple encounters.
With the significant increase in the number of satellite constellations and GEO objects, long-ter... more With the significant increase in the number of satellite constellations and GEO objects, long-term encounters become common. Such geometries are characterized by a curvilinear relative motion and important position and velocity uncertainties.
We first determine the relative velocity limits between the linear and non-linear encounters and the limits between negligible or not negligible velocity uncertainties. We then propose an algorithm combining a Monte Carlo and an importance sampling method to compute the collision probability for the curvilinear domain. We finally apply this algorithm to various encounters to demonstrate its efficiency in terms of accuracy and computation time.
Acta Astronautica, 2021
Abstract This paper describes a process for identifying the intact objects in orbit that (a) pose... more Abstract This paper describes a process for identifying the intact objects in orbit that (a) pose the greatest debris-generating potential risk to operational satellites or (b) would reduce the risk the most if they were removed or prevented from colliding with each other (i.e., remediated). To accomplish this, a number of diverse, international space organizations were solicited to contribute their lists of the 50 statistically-most-concerning objects. The results of the multiple algorithms are compared, a composite ranked list is provided, and the significance of the consolidated list is presented including critical assumptions and key factors in determining this “hit list.” It is found that the four primary factors used in these processes are mass, encounter rates, orbital lifetime, and proximity to operational satellites. This cooperative international assessment provides a useful ranking of the most hazardous massive derelicts in low Earth orbit as a prioritized list for remediation to (1) enhance space safety and (2) assure long-term space sustainability. This will hopefully catalyze international action in debris remediation.
Objects in Low-Earth Orbits (LEO) and Highly Elliptical Orbits (HEO) are subject to decay and re-... more Objects in Low-Earth Orbits (LEO) and Highly Elliptical Orbits (HEO) are subject to decay and re-entry into the atmosphere due mainly to the drag force. While being this process the best solution to avoid the proliferation of debris in space and to ensure the future sustainability of space activities, it implies a certain amount of risk as many of these reentries are done in an uncontrolled manner. In order to have a better insight on the objects reentering the Earth’s atmosphere, in short and middle term, and on the risk posed by these re-entries, CNES has developed a tool named OPERA (Outil de PrEvision des dates des Rentrées Atmosphèriques non contrôlées). This paper will concentrate on the prediction of the in-orbit lifetime of a space object, based on publicly available TLE (Two Line Elements sets) data, as it has been implemented in OPERA. To this purpose, several operations are needed prior to the computation of the residual in-orbit lifetime of such object, by the propagatio...
Since the launch of Sputnik-I in 1957, the amount of space debris in Earth׳s orbit has increased ... more Since the launch of Sputnik-I in 1957, the amount of space debris in Earth׳s orbit has increased continuously. Historically, besides abandoned intact objects (spacecraft and orbital stages), the primary sources of space debris in Earth׳s orbit were (i) accidental and intentional break-ups which produced long-lasting debris and (ii) debris released intentionally during the operation of launch vehicle orbital stages and spacecraft. In the future, fragments generated by collisions are expected to become a significant source as well.
In this context, and from a purely mathematical point of view, the orbital debris population in Low Earth Orbit (LEO) should be intrinsically unstable, due to the physics of mutual collisions and the relative ineffectiveness of natural sink mechanisms above~700 km. Therefore, the real question should not be “if”, but “when” the exponential growth of the space debris population is supposed to start. From a practical point of view, and in order to answer the previous question, since the end of the 1980׳s several sophisticated long-term debris evolutionary models have been developed.
Unfortunately, the predictions performed with such models, in particular beyond a few decades, are affected by considerable uncertainty. Such uncertainty comes from a relative important number of variables that being either under the partial control or completely out of the control of modellers, introduce a variability on the long-term simulation of the space debris population which cannot be captured with standard Monte Carlo statistics.
The objective of this paper is to present and discuss many of the uncertainty sources affecting the long-term predictions done with evolutionary models, in order to serve as a roadmap for the uncertainty and the statistical robustness analysis of the long-term evolution of the space debris population.
Since 1994, where COPUOS considered for the first time, on a priority basis, matters associated w... more Since 1994, where COPUOS considered for the first time, on a priority basis, matters associated with space debris, many countries and international organization have agreed, via the publication of space debris mitigation guidelines, on the need to mitigate the risk posed by the space debris environment. At international level, the Inter Agencies space Debris Committee (IADC) published its mitigation guidelines in 2002 and COPUOS adopted its space debris mitigation guidelines in 2007. In France, the French Space Operations Act (FSOA), which also deals with this problematic, came into force in 2010.
The work presented on this paper aims to investigate the global compliance of mitigation guidelines by space operators over a 13 years period (2000 – 2012). We are particularly interested in studying the expected decrease of the mid or long term risk in LEO, through the application of the 25 year rule or the re-orbitation above the LEO graveyard orbit.
First of all we have gathered orbital information, mainly from publicly available sources, of satellites and launcher elements crossing or near the LEO protected region (defined by an altitude lower than 2000 Km). From the previous sub-set of space objects, we have identified those arriving to end of mission between 2000 and 2012 by detecting the last orbital maneuver. This has been possible by the development of maneuver detection algorithms, which from the analysis of temporal series of orbital data are able to compute the manoeuvres dates and magnitude.
For the space objects arriving to end of mission between 2000 and 2012 that have not decayed yet, the knowledge of their physical characteristics as the ballistic coefficient, is necessary to estimate a re-entry duration. In order to obtain such information, specific algorithms have been developed and validated in the frame of this study.
Finally, the orbital lifetime of each space object has been computed under the standard methods defined in the framework of the FSOA for what concerns solar activity prediction.
One of the main results of our study consists in the rate of compliance of LEO mitigation guidelines for each year between 2000 and 2012, for spacecrafts as well as for launcher elements. This allows us to analyze the existence of trends showing the improvement of the mitigation guidelines compliance over the years.
Objects in Low-Earth Orbits (LEO) and Highly Elliptical Orbits (HEO) are subject to decay and re-... more Objects in Low-Earth Orbits (LEO) and Highly Elliptical Orbits (HEO) are subject to decay and re-entry into the atmosphere due mainly to the drag force. While being this process the best solution to avoid the proliferation of debris in space and to ensure the future sustainability of space activities, it implies a certain amount of risk as many of these reentries are done in an uncontrolled manner.
In order to have a better insight on the objects reentering the Earth’s atmosphere, in short and middle term, and on the risk posed by these re-entries, CNES has developed a tool named OPERA (Outil de PrEvision des dates des Rentrées Atmosphèriques non contrôlées).
This paper will concentrate on the prediction of the in-orbit lifetime of a space object, based on publicly available TLE (Two Line Elements sets) data, as it has been implemented in OPERA.
To this purpose, several operations are needed prior to the computation of the residual in-orbit lifetime of such object, by the propagation of its orbital position up to re-entry.
These operations include the pre-processing of the TLE data by filtering their outliers and detecting maneuvers, as only non-maneuverable objects are considered for the analysis, the preliminary estimation of objects area-to-mass ratio and the final estimation of the orbits based on a weighted least-squares algorithm taking the TLE states as input pseudo-observations. Additionally, the accuracy (estimation error) of the results obtained for known past reentries will be presented.
With the increase on the number of satellite constellations, multiple encounters become more and ... more With the increase on the number of satellite constellations, multiple encounters become more and more common. In the
event of this type of encounters and in order to compute the overall collision probability, it is necessary to analyse the collision risk of all the encounters as a whole instead of taking them into account separately.
A N encounters collision probability may be computed by Monte Carlo method. Unfortunately, this could be extremely expensive in term of computation. We develop two criteria to avoid as much as possible Monte Carlo trials. The first criterion is based on the bracketing of the real probability by two probabilities that may be computed with individual encounter probabilities. This criterion is useful to probe the collision probability magnitude. In many cases, we observe that up to some security threshold, the N encounters collision probability is equal to the summation of the individual collision probability.
We develop a geometrical criterion to predict the threshold domain where we can compute the N encounters collision probability through an addition of individual collision probability.
In this paper, we expose the method to compute the two criteria, there meaning and illustrate their use on some cases of multiple encounters.
With the significant increase in the number of satellite constellations and GEO objects, long-ter... more With the significant increase in the number of satellite constellations and GEO objects, long-term encounters become common. Such geometries are characterized by a curvilinear relative motion and important position and velocity uncertainties.
We first determine the relative velocity limits between the linear and non-linear encounters and the limits between negligible or not negligible velocity uncertainties. We then propose an algorithm combining a Monte Carlo and an importance sampling method to compute the collision probability for the curvilinear domain. We finally apply this algorithm to various encounters to demonstrate its efficiency in terms of accuracy and computation time.