ABSTRACT During the last 40 years, the mass of the artificial objects in orbit increased quite st... more ABSTRACT During the last 40 years, the mass of the artificial objects in orbit increased quite steadily at the rate of about 145 metric tons annually, leading to about 7000 metric tons. Most of the cross-sectional area and mass (97% in low Earth orbit) is concentrated in about 4500 intact abandoned objects plus a further 1000 operational spacecraft. Analyses have shown that the most effective mitigation strategy should focus on the disposal of objects with larger crosssectional area and mass from densely populated orbits. Recent NASA results have shown that the worldwide adoption of mitigation measures in conjunction with active yearly removal of approximately 0.20.5% of the abandoned objects would stabilize the debris population. Targets would have typical masses between 500 and 1000 kg in the case of spacecraft, and of more than 1000 kg for rocket upper stages. In the case of Cosmos-3M second stages, more than one object is located nearly in the same orbital plane. This provides the opportunity of multiremoval missions, more suitable for yearly removal rate and cost reduction needs. This paper deals with the feasibility study of a mission for the active removal of large abandoned objects in low Earth orbit. In particular, a mission is studied in which the removal of two Cosmos-3M second stages, that are numerous in low Earth orbit, is considered. The removal system relies on a Chaser spacecraft which performs rendezvous maneuvers with the two targets. The first Cosmos-3M stage is captured and an autonomous de-orbiting kit, carried by the Chaser, is attached to it. The de-orbiting kit consists of a Hybrid Propulsion Module, which is ignited to perform stage disposal and controlled reentry after Chaser separation. Then, the second Cosmos-3M stage is captured and, in this case, the primary propulsion system of the Chaser is used for the disposal of the mated configuration. Critical mission aspects and related technologies are investigated at a preliminary level. In particular, an innovative electro-adhesive system for target capture, mechanical systems for the hard docking with the target and a hybrid propulsion technology suitable for rendezvous, de-orbiting and controlled reentry operations are analyzed. This is performed on the basis of a preliminary mission profile, in which suitable rendezvous and disposal strategies have been considered and investigated by numerical analysis. A preliminary system mass budget is also performed, showing that the Chaser overall mass is about 1350 kg, including a primary propulsion system of about 300 kg, and a de-orbiting kit with a mass of about 200 kg. The system designed results suitable to be launched with VEGA, actually the cheapest European space launcher.
In recent years, the development of active removal missions, to face the growing risk of catastro... more In recent years, the development of active removal missions, to face the growing risk of catastrophic collisions and new debris generation due to the high density of orbital debris in LEO, is widely discussed in the international space community. Besides legal and political issues, active removal solutions are strongly hampered by the high costs involved. Chemical propulsion might represent the preferred way to carry out the controlled reentry of large abandoned objects, and, in the perspective of cost reduction, hybrid rocket technology is considered a valuable option, due to the potential lower fabrication and operational costs, if compared with bipropellant liquid systems. The possibility to use nontoxic propellants, besides their lower prices, reduces the complexity of handling, storability, and loading operations, decreasing the connected costs and avoiding the need of a special staff. Solid rocket technology allows for very small and compact motor units, although without throttleability and reignition capability and characterized by lower safety level than liquid and hybrid systems. This study deals with the preliminary design and mass budget of solid, liquid, and hybrid propulsion modules, as well as their comparison, to be used for active removal of large abandoned rockets in LEO.
During the last 40 years, the mass of orbiting objects increased at the rate of about 145 metric ... more During the last 40 years, the mass of orbiting objects increased at the rate of about 145 metric tons annually, leading to a total of approximately 7000 metric tons. Most of the cross-sectional area and mass (97% in low Earth orbit, LEO) is concentrated in about 4500 intact objects, i.e. abandoned spacecraft and rocket bodies, plus a further 1000 operational spacecrafts. Numerical simulations show that the most effective way to prevent an exponential growth of the cataloged debris population would be to remove enough cross-sectional area and mass from densely populated orbits. According to the most recent NASA results, the active yearly removal of approximately 0.1% of the abandoned intact objects would be sufficient to stabilize the cataloged debris in LEO. The typical targets for removal would have masses between 500 and 1000 kg, for spacecraft, and of more than 1000 kg, for rocket upper stages. This paper investigates a space mission concept for active removal of abandoned Cosmos-3M second stages from LEO. The proposed concept relies on flying a multi-removal space platform carrying a number of Hybrid Propulsion Modules (HPMs). After capture, a HPM is installed on the debris, which is then de-orbited in a controlled fashion. The estimated mass of a single HPM results about 200 kg, making possible a multi-removal mission by means of a low-cost class-launcher.
During the last 40 years, the mass of the artificial objects in orbit increased quite steadily at... more During the last 40 years, the mass of the artificial objects in orbit increased quite steadily at the rate of about 145 metric tons annually, leading to about 7000 metric tons. Most of the cross-sectional area and mass (97% in low Earth orbit) is concentrated in about 4500 intact abandoned objects plus a further 1000 operational spacecraft. Analyses have shown that the most effective mitigation strategy should focus on the disposal of objects with larger cross-sectional area and mass from densely populated orbits. Recent NASA results have shown that the worldwide adoption of mitigation measures in conjunction with active yearly removal of approximately 0.2-0.5% of the abandoned objects would stabilize the debris population. Targets would have typical masses between 500 and 1000 kg in the case of spacecraft, and of more than 1000 kg for rocket upper stages. In the case of Cosmos-3M second stages, more than one object is located nearly in the same orbital plane. This provides the opportunity of multi-removal missions, more suitable for yearly removal rate and cost reduction needs. This paper deals with the feasibility study of a mission for the active removal of large abandoned objects in low Earth orbit. In particular, a mission is studied in which the removal of two Cosmos-3M second stages, that are numerous in low Earth orbit, is considered. The removal system relies on a Chaser spacecraft which performs rendezvous maneuvers with the two targets. The first Cosmos-3M stage is captured and an autonomous de-orbiting kit, carried by the Chaser, is attached to it. The de-orbiting kit includes a Hybrid Propulsion Module, which is remotely ignited to perform stage disposal and controlled reentry after Chaser separation. Then, the second Cosmos-3M stage is captured and, in this case, the primary propulsion system of the Chaser is used for the disposal of the mated configuration. Critical mission aspects and related technologies are investigated at a preliminary level. In particular, an innovative electro-adhesive system for target capture, a mechanical system for the hard docking with the target and a hybrid propulsion system suitable for rendezvous, deorbiting and controlled reentry operations are analyzed. This is performed on the basis 1 of a preliminary mission profile, in which suitable rendezvous and disposal strategies have been considered and investigated by numerical analysis. A preliminary system mass budget is also performed, showing that the Chaser overall mass is about 1350 kg, including a primary propulsion system of about 300 kg and a de-orbiting kit with a mass of about 200 kg. This system is suitable to be launched with VEGA, actually the cheapest European space launcher.
Following the catastrophic collisional breakups of three intact spacecraft (Fengyun 1C, Cosmos 22... more Following the catastrophic collisional breakups of three intact spacecraft (Fengyun 1C, Cosmos 2251, and Iridium 33) occurred in low-Earth orbit, a detailed analysis was carried out, with a dedicated software tool (SDIRAT ¡ Space Debris Impact Risk Assessment Tool), in order to evaluate the additional impact §ux of cataloged objects on the satellites of two operational constellations in high inclination orbits, Iridium and COSMO-SkyMed. As of May 1, 2011, the §ux increase with respect to the debris background was 160%, on average, for the Iridium satellites, distributed on six equally spaced orbit planes at 781 km, and 47% at the altitude of the COSMO-SkyMed constellation, using a single orbit plane at 623 km.
A concept for a flight demonstration experiment for active debris removal is presented. It is bas... more A concept for a flight demonstration experiment for active debris removal is presented. It is based on the exploitation of the launch of a payload in its desired orbit, then followed by the active debris removal demonstration experiment using the leftover resources of the upper stage, in terms of remaining propellant and electric battery residual lifetime, and a specialized piggy-back payload for the far guidance and acquisition of the selected target, the engagement and docking with it, the stabilization of the docked complex and, finally, its controlled de-orbiting. The basic components of the system will consist of a Transport and Docking Module (TDM), with its own autonomous propulsion, guidance, control and docking mechanism, and a retractable tether system, with a controllable drum for deployment and retraction, connecting the upper stage of the launcher with TDM. Concerning the choice of the target for the active debris removal demonstration experiment, ideal candidates are r...
The analysis of different disposal strategies for the spacecraft belonging to the Global Navigati... more The analysis of different disposal strategies for the spacecraft belonging to the Global Navigation Satellite Systems (GNSS), with particular emphasis on the European Galileo system is the aim of this study. The results of numerical simulations of the long term evolution scenarios, implementing different disposal strategies, are shown and discussed. A detailed analysis of the collision risk and manoeuvres need, related to the different scenarios, was performed. In terms of the long term evolution, the scenarios where the orbital instabilities are exploited to remove the objects from the operational regions seems favourite. That is, if the focus is on the long term sustainability of the space environment, the possibility to dilute the collision risk and to aim at the re-entry in the atmosphere of a subset of the disposed GNSS spacecraft is the most attractive. The most "problematic" constellations are Glonass and Beidou. This conclusion is driven by the future launch traffi...
In the last years significant understandings in the knowledge of the dynamics of the MEO satellit... more In the last years significant understandings in the knowledge of the dynamics of the MEO satellites were achieved. Much work was done in the analysis of viable disposal strategies and technologies for the spacecraft belonging to the Global Navigation Satellite Systems (GNSS), with particular emphasis on the European Galileo system. In the framework of an ESA-ESOC Contract an extensive numerical simulations of different long term evolution scenarios, implementing different disposal strategies were performed. A detailed analysis of the collision risk and manoeuvres need, related to the different scenarios, was performed. In terms of the long term evolution, the scenarios where the orbital instabilities are exploited to remove the objects from the operational regions seems favourite. That is, if the focus is on the long term sustainability of the space environment, the possibility to dilute the collision risk and to aim at the re-entry in the atmosphere of a subset of the disposed GNSS...
In order to evaluate the potential environmental criticality, regarding the evolution of orbital ... more In order to evaluate the potential environmental criticality, regarding the evolution of orbital debris, of the objects lost or abandoned in low Earth orbit, a new normalized and dimensionless ranking index was presented, using as benchmark a nearly 1-ton object placed into an 800 km sun-synchronous orbit. It was applied to 58 objects with a mean altitude in between 600 and 1000 km and with a dry mass greater than 3000 kg. They accounted for about 11% of the mass present in low Earth orbit, operational spacecraft included. The maximum value found corresponded to the massive second stage of a Zenit launcher, abandoned close to 1000 km. Envisat ranked first among the spacecraft no longer operational, but only 22 in the group considered, after 20 Zenit second stages and a CZ-2C rocket body. Most of the mass with a criticality index greater than 1, i.e. 90%, was concentrated at 830 ± 40 km.
The long term influence of objects crossing or abandoned in GEO was evaluated, based on current p... more The long term influence of objects crossing or abandoned in GEO was evaluated, based on current practices, using the new Space Debris Mitigation mo del SDM 4.0. It was the latest version of a long term evolution code originally developed in the early 19 90’s, specifically designed to model with high accuracy t he high Earth orbit regimes. Starting from the MASTER-2005 debris population, th e long term evolution of the GEO environment was simulated under a few realistic scenarios, based on increasingly aggressive mitigation strategies. Beyo nd the high eccentricity objects, also the influence o f the rocket stages separated from GEO spacecraft and lef t in geosynchronous drift orbits was analyzed. The main mitigation measures considered included the re-orbi ting of GEO spacecraft at the end-of-life in the super-G EO graveyard zone, the de-orbiting of GTO/HEO upper stages and the re-orbiting of the rocket stages usu ally abandoned in drift orbits. These simulations allowed the quantit...
After a brief review of the risk represented by the uncontrolled re-entry of sizable spacecraft a... more After a brief review of the risk represented by the uncontrolled re-entry of sizable spacecraft and upper stages, a statistical analysis of 316 predictions issued during the first 20 IADC test campaigns was presented, in order to characterize the errors affecting the estimate of the residual lifetime in the couple of weeks preceding the re-entry. Overall, the mean prediction error was about 10%, increasing to 15% in the last 6 hours. The re-entry predictions for upper stages resulted more accurate than average, with a mean error of about 5%, increasing to approximately 8% during the last day. In view of the statistical distribution of the predictions, an uncertainty window able to guarantee a confidence level of 90% should generally adopt an amplitude of about ±20% around the estimated nominal re-entry time, to be raised to about ±25% in the couple of days ahead of re-entry. An uncertainty window amplitude of ±30% would be, instead, needed to achieve a confidence level ≥ 95%.
Journal of Space Safety Engineering (JSSE) provides an authoritative source of information in the... more Journal of Space Safety Engineering (JSSE) provides an authoritative source of information in the field of space safety design, research and development. It serves applied scientists, engineers, policy makers and safety advocates with a platform to develop, promote and coordinate the science, technology and practice of space safety. JSSE seeks to establish channels of communication between industry, academy and government in the field of space safety and sustainability.
TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, 2008
The long-term evolution, over 54 years, of a sample of objects released in geostationary orbit wi... more The long-term evolution, over 54 years, of a sample of objects released in geostationary orbit with area-to-mass ratios (A=M) up to 50 m 2 /kg was analyzed, taking into account geopotential harmonics (8 Â 8), luni-solar perturbations, direct solar radiation pressure with eclipses and, when applicable, air drag. The results indicate that objects with A=M up to 25 m 2 /kg might explain the recently discovered debris population with mean motions of about one revolution per day and orbital eccentricities as high as 0.6. At so large area-to-mass ratios, the orbital evolution was mainly driven by solar radiation pressure. Although the general behavior observed was the same in all studied cases, the details of the evolution depended on the initial conditions. The simulated objects with A=M 37 m 2 /kg were characterized by an orbital lifetime > 54 years, while for A=M > 40{45 m 2 /kg, the exact value again depending on the initial conditions, the lifetime dropped rapidly to a few months with increasing values of the area-to-mass ratio. A growth of A=M had, as a consequence, a larger amplitude of the yearly oscillations that dominate the eccentricity evolution, in addition to a faster and wider orbit pole clockwise precession.
ABSTRACT During the last 40 years, the mass of the artificial objects in orbit increased quite st... more ABSTRACT During the last 40 years, the mass of the artificial objects in orbit increased quite steadily at the rate of about 145 metric tons annually, leading to about 7000 metric tons. Most of the cross-sectional area and mass (97% in low Earth orbit) is concentrated in about 4500 intact abandoned objects plus a further 1000 operational spacecraft. Analyses have shown that the most effective mitigation strategy should focus on the disposal of objects with larger crosssectional area and mass from densely populated orbits. Recent NASA results have shown that the worldwide adoption of mitigation measures in conjunction with active yearly removal of approximately 0.20.5% of the abandoned objects would stabilize the debris population. Targets would have typical masses between 500 and 1000 kg in the case of spacecraft, and of more than 1000 kg for rocket upper stages. In the case of Cosmos-3M second stages, more than one object is located nearly in the same orbital plane. This provides the opportunity of multiremoval missions, more suitable for yearly removal rate and cost reduction needs. This paper deals with the feasibility study of a mission for the active removal of large abandoned objects in low Earth orbit. In particular, a mission is studied in which the removal of two Cosmos-3M second stages, that are numerous in low Earth orbit, is considered. The removal system relies on a Chaser spacecraft which performs rendezvous maneuvers with the two targets. The first Cosmos-3M stage is captured and an autonomous de-orbiting kit, carried by the Chaser, is attached to it. The de-orbiting kit consists of a Hybrid Propulsion Module, which is ignited to perform stage disposal and controlled reentry after Chaser separation. Then, the second Cosmos-3M stage is captured and, in this case, the primary propulsion system of the Chaser is used for the disposal of the mated configuration. Critical mission aspects and related technologies are investigated at a preliminary level. In particular, an innovative electro-adhesive system for target capture, mechanical systems for the hard docking with the target and a hybrid propulsion technology suitable for rendezvous, de-orbiting and controlled reentry operations are analyzed. This is performed on the basis of a preliminary mission profile, in which suitable rendezvous and disposal strategies have been considered and investigated by numerical analysis. A preliminary system mass budget is also performed, showing that the Chaser overall mass is about 1350 kg, including a primary propulsion system of about 300 kg, and a de-orbiting kit with a mass of about 200 kg. The system designed results suitable to be launched with VEGA, actually the cheapest European space launcher.
ABSTRACT During the last 40 years, the mass of the artificial objects in orbit increased quite st... more ABSTRACT During the last 40 years, the mass of the artificial objects in orbit increased quite steadily at the rate of about 145 metric tons annually, leading to about 7000 metric tons. Most of the cross-sectional area and mass (97% in low Earth orbit) is concentrated in about 4500 intact abandoned objects plus a further 1000 operational spacecraft. Analyses have shown that the most effective mitigation strategy should focus on the disposal of objects with larger crosssectional area and mass from densely populated orbits. Recent NASA results have shown that the worldwide adoption of mitigation measures in conjunction with active yearly removal of approximately 0.20.5% of the abandoned objects would stabilize the debris population. Targets would have typical masses between 500 and 1000 kg in the case of spacecraft, and of more than 1000 kg for rocket upper stages. In the case of Cosmos-3M second stages, more than one object is located nearly in the same orbital plane. This provides the opportunity of multiremoval missions, more suitable for yearly removal rate and cost reduction needs. This paper deals with the feasibility study of a mission for the active removal of large abandoned objects in low Earth orbit. In particular, a mission is studied in which the removal of two Cosmos-3M second stages, that are numerous in low Earth orbit, is considered. The removal system relies on a Chaser spacecraft which performs rendezvous maneuvers with the two targets. The first Cosmos-3M stage is captured and an autonomous de-orbiting kit, carried by the Chaser, is attached to it. The de-orbiting kit consists of a Hybrid Propulsion Module, which is ignited to perform stage disposal and controlled reentry after Chaser separation. Then, the second Cosmos-3M stage is captured and, in this case, the primary propulsion system of the Chaser is used for the disposal of the mated configuration. Critical mission aspects and related technologies are investigated at a preliminary level. In particular, an innovative electro-adhesive system for target capture, mechanical systems for the hard docking with the target and a hybrid propulsion technology suitable for rendezvous, de-orbiting and controlled reentry operations are analyzed. This is performed on the basis of a preliminary mission profile, in which suitable rendezvous and disposal strategies have been considered and investigated by numerical analysis. A preliminary system mass budget is also performed, showing that the Chaser overall mass is about 1350 kg, including a primary propulsion system of about 300 kg, and a de-orbiting kit with a mass of about 200 kg. The system designed results suitable to be launched with VEGA, actually the cheapest European space launcher.
In recent years, the development of active removal missions, to face the growing risk of catastro... more In recent years, the development of active removal missions, to face the growing risk of catastrophic collisions and new debris generation due to the high density of orbital debris in LEO, is widely discussed in the international space community. Besides legal and political issues, active removal solutions are strongly hampered by the high costs involved. Chemical propulsion might represent the preferred way to carry out the controlled reentry of large abandoned objects, and, in the perspective of cost reduction, hybrid rocket technology is considered a valuable option, due to the potential lower fabrication and operational costs, if compared with bipropellant liquid systems. The possibility to use nontoxic propellants, besides their lower prices, reduces the complexity of handling, storability, and loading operations, decreasing the connected costs and avoiding the need of a special staff. Solid rocket technology allows for very small and compact motor units, although without throttleability and reignition capability and characterized by lower safety level than liquid and hybrid systems. This study deals with the preliminary design and mass budget of solid, liquid, and hybrid propulsion modules, as well as their comparison, to be used for active removal of large abandoned rockets in LEO.
During the last 40 years, the mass of orbiting objects increased at the rate of about 145 metric ... more During the last 40 years, the mass of orbiting objects increased at the rate of about 145 metric tons annually, leading to a total of approximately 7000 metric tons. Most of the cross-sectional area and mass (97% in low Earth orbit, LEO) is concentrated in about 4500 intact objects, i.e. abandoned spacecraft and rocket bodies, plus a further 1000 operational spacecrafts. Numerical simulations show that the most effective way to prevent an exponential growth of the cataloged debris population would be to remove enough cross-sectional area and mass from densely populated orbits. According to the most recent NASA results, the active yearly removal of approximately 0.1% of the abandoned intact objects would be sufficient to stabilize the cataloged debris in LEO. The typical targets for removal would have masses between 500 and 1000 kg, for spacecraft, and of more than 1000 kg, for rocket upper stages. This paper investigates a space mission concept for active removal of abandoned Cosmos-3M second stages from LEO. The proposed concept relies on flying a multi-removal space platform carrying a number of Hybrid Propulsion Modules (HPMs). After capture, a HPM is installed on the debris, which is then de-orbited in a controlled fashion. The estimated mass of a single HPM results about 200 kg, making possible a multi-removal mission by means of a low-cost class-launcher.
During the last 40 years, the mass of the artificial objects in orbit increased quite steadily at... more During the last 40 years, the mass of the artificial objects in orbit increased quite steadily at the rate of about 145 metric tons annually, leading to about 7000 metric tons. Most of the cross-sectional area and mass (97% in low Earth orbit) is concentrated in about 4500 intact abandoned objects plus a further 1000 operational spacecraft. Analyses have shown that the most effective mitigation strategy should focus on the disposal of objects with larger cross-sectional area and mass from densely populated orbits. Recent NASA results have shown that the worldwide adoption of mitigation measures in conjunction with active yearly removal of approximately 0.2-0.5% of the abandoned objects would stabilize the debris population. Targets would have typical masses between 500 and 1000 kg in the case of spacecraft, and of more than 1000 kg for rocket upper stages. In the case of Cosmos-3M second stages, more than one object is located nearly in the same orbital plane. This provides the opportunity of multi-removal missions, more suitable for yearly removal rate and cost reduction needs. This paper deals with the feasibility study of a mission for the active removal of large abandoned objects in low Earth orbit. In particular, a mission is studied in which the removal of two Cosmos-3M second stages, that are numerous in low Earth orbit, is considered. The removal system relies on a Chaser spacecraft which performs rendezvous maneuvers with the two targets. The first Cosmos-3M stage is captured and an autonomous de-orbiting kit, carried by the Chaser, is attached to it. The de-orbiting kit includes a Hybrid Propulsion Module, which is remotely ignited to perform stage disposal and controlled reentry after Chaser separation. Then, the second Cosmos-3M stage is captured and, in this case, the primary propulsion system of the Chaser is used for the disposal of the mated configuration. Critical mission aspects and related technologies are investigated at a preliminary level. In particular, an innovative electro-adhesive system for target capture, a mechanical system for the hard docking with the target and a hybrid propulsion system suitable for rendezvous, deorbiting and controlled reentry operations are analyzed. This is performed on the basis 1 of a preliminary mission profile, in which suitable rendezvous and disposal strategies have been considered and investigated by numerical analysis. A preliminary system mass budget is also performed, showing that the Chaser overall mass is about 1350 kg, including a primary propulsion system of about 300 kg and a de-orbiting kit with a mass of about 200 kg. This system is suitable to be launched with VEGA, actually the cheapest European space launcher.
Following the catastrophic collisional breakups of three intact spacecraft (Fengyun 1C, Cosmos 22... more Following the catastrophic collisional breakups of three intact spacecraft (Fengyun 1C, Cosmos 2251, and Iridium 33) occurred in low-Earth orbit, a detailed analysis was carried out, with a dedicated software tool (SDIRAT ¡ Space Debris Impact Risk Assessment Tool), in order to evaluate the additional impact §ux of cataloged objects on the satellites of two operational constellations in high inclination orbits, Iridium and COSMO-SkyMed. As of May 1, 2011, the §ux increase with respect to the debris background was 160%, on average, for the Iridium satellites, distributed on six equally spaced orbit planes at 781 km, and 47% at the altitude of the COSMO-SkyMed constellation, using a single orbit plane at 623 km.
A concept for a flight demonstration experiment for active debris removal is presented. It is bas... more A concept for a flight demonstration experiment for active debris removal is presented. It is based on the exploitation of the launch of a payload in its desired orbit, then followed by the active debris removal demonstration experiment using the leftover resources of the upper stage, in terms of remaining propellant and electric battery residual lifetime, and a specialized piggy-back payload for the far guidance and acquisition of the selected target, the engagement and docking with it, the stabilization of the docked complex and, finally, its controlled de-orbiting. The basic components of the system will consist of a Transport and Docking Module (TDM), with its own autonomous propulsion, guidance, control and docking mechanism, and a retractable tether system, with a controllable drum for deployment and retraction, connecting the upper stage of the launcher with TDM. Concerning the choice of the target for the active debris removal demonstration experiment, ideal candidates are r...
The analysis of different disposal strategies for the spacecraft belonging to the Global Navigati... more The analysis of different disposal strategies for the spacecraft belonging to the Global Navigation Satellite Systems (GNSS), with particular emphasis on the European Galileo system is the aim of this study. The results of numerical simulations of the long term evolution scenarios, implementing different disposal strategies, are shown and discussed. A detailed analysis of the collision risk and manoeuvres need, related to the different scenarios, was performed. In terms of the long term evolution, the scenarios where the orbital instabilities are exploited to remove the objects from the operational regions seems favourite. That is, if the focus is on the long term sustainability of the space environment, the possibility to dilute the collision risk and to aim at the re-entry in the atmosphere of a subset of the disposed GNSS spacecraft is the most attractive. The most "problematic" constellations are Glonass and Beidou. This conclusion is driven by the future launch traffi...
In the last years significant understandings in the knowledge of the dynamics of the MEO satellit... more In the last years significant understandings in the knowledge of the dynamics of the MEO satellites were achieved. Much work was done in the analysis of viable disposal strategies and technologies for the spacecraft belonging to the Global Navigation Satellite Systems (GNSS), with particular emphasis on the European Galileo system. In the framework of an ESA-ESOC Contract an extensive numerical simulations of different long term evolution scenarios, implementing different disposal strategies were performed. A detailed analysis of the collision risk and manoeuvres need, related to the different scenarios, was performed. In terms of the long term evolution, the scenarios where the orbital instabilities are exploited to remove the objects from the operational regions seems favourite. That is, if the focus is on the long term sustainability of the space environment, the possibility to dilute the collision risk and to aim at the re-entry in the atmosphere of a subset of the disposed GNSS...
In order to evaluate the potential environmental criticality, regarding the evolution of orbital ... more In order to evaluate the potential environmental criticality, regarding the evolution of orbital debris, of the objects lost or abandoned in low Earth orbit, a new normalized and dimensionless ranking index was presented, using as benchmark a nearly 1-ton object placed into an 800 km sun-synchronous orbit. It was applied to 58 objects with a mean altitude in between 600 and 1000 km and with a dry mass greater than 3000 kg. They accounted for about 11% of the mass present in low Earth orbit, operational spacecraft included. The maximum value found corresponded to the massive second stage of a Zenit launcher, abandoned close to 1000 km. Envisat ranked first among the spacecraft no longer operational, but only 22 in the group considered, after 20 Zenit second stages and a CZ-2C rocket body. Most of the mass with a criticality index greater than 1, i.e. 90%, was concentrated at 830 ± 40 km.
The long term influence of objects crossing or abandoned in GEO was evaluated, based on current p... more The long term influence of objects crossing or abandoned in GEO was evaluated, based on current practices, using the new Space Debris Mitigation mo del SDM 4.0. It was the latest version of a long term evolution code originally developed in the early 19 90’s, specifically designed to model with high accuracy t he high Earth orbit regimes. Starting from the MASTER-2005 debris population, th e long term evolution of the GEO environment was simulated under a few realistic scenarios, based on increasingly aggressive mitigation strategies. Beyo nd the high eccentricity objects, also the influence o f the rocket stages separated from GEO spacecraft and lef t in geosynchronous drift orbits was analyzed. The main mitigation measures considered included the re-orbi ting of GEO spacecraft at the end-of-life in the super-G EO graveyard zone, the de-orbiting of GTO/HEO upper stages and the re-orbiting of the rocket stages usu ally abandoned in drift orbits. These simulations allowed the quantit...
After a brief review of the risk represented by the uncontrolled re-entry of sizable spacecraft a... more After a brief review of the risk represented by the uncontrolled re-entry of sizable spacecraft and upper stages, a statistical analysis of 316 predictions issued during the first 20 IADC test campaigns was presented, in order to characterize the errors affecting the estimate of the residual lifetime in the couple of weeks preceding the re-entry. Overall, the mean prediction error was about 10%, increasing to 15% in the last 6 hours. The re-entry predictions for upper stages resulted more accurate than average, with a mean error of about 5%, increasing to approximately 8% during the last day. In view of the statistical distribution of the predictions, an uncertainty window able to guarantee a confidence level of 90% should generally adopt an amplitude of about ±20% around the estimated nominal re-entry time, to be raised to about ±25% in the couple of days ahead of re-entry. An uncertainty window amplitude of ±30% would be, instead, needed to achieve a confidence level ≥ 95%.
Journal of Space Safety Engineering (JSSE) provides an authoritative source of information in the... more Journal of Space Safety Engineering (JSSE) provides an authoritative source of information in the field of space safety design, research and development. It serves applied scientists, engineers, policy makers and safety advocates with a platform to develop, promote and coordinate the science, technology and practice of space safety. JSSE seeks to establish channels of communication between industry, academy and government in the field of space safety and sustainability.
TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, 2008
The long-term evolution, over 54 years, of a sample of objects released in geostationary orbit wi... more The long-term evolution, over 54 years, of a sample of objects released in geostationary orbit with area-to-mass ratios (A=M) up to 50 m 2 /kg was analyzed, taking into account geopotential harmonics (8 Â 8), luni-solar perturbations, direct solar radiation pressure with eclipses and, when applicable, air drag. The results indicate that objects with A=M up to 25 m 2 /kg might explain the recently discovered debris population with mean motions of about one revolution per day and orbital eccentricities as high as 0.6. At so large area-to-mass ratios, the orbital evolution was mainly driven by solar radiation pressure. Although the general behavior observed was the same in all studied cases, the details of the evolution depended on the initial conditions. The simulated objects with A=M 37 m 2 /kg were characterized by an orbital lifetime > 54 years, while for A=M > 40{45 m 2 /kg, the exact value again depending on the initial conditions, the lifetime dropped rapidly to a few months with increasing values of the area-to-mass ratio. A growth of A=M had, as a consequence, a larger amplitude of the yearly oscillations that dominate the eccentricity evolution, in addition to a faster and wider orbit pole clockwise precession.
ABSTRACT During the last 40 years, the mass of the artificial objects in orbit increased quite st... more ABSTRACT During the last 40 years, the mass of the artificial objects in orbit increased quite steadily at the rate of about 145 metric tons annually, leading to about 7000 metric tons. Most of the cross-sectional area and mass (97% in low Earth orbit) is concentrated in about 4500 intact abandoned objects plus a further 1000 operational spacecraft. Analyses have shown that the most effective mitigation strategy should focus on the disposal of objects with larger crosssectional area and mass from densely populated orbits. Recent NASA results have shown that the worldwide adoption of mitigation measures in conjunction with active yearly removal of approximately 0.20.5% of the abandoned objects would stabilize the debris population. Targets would have typical masses between 500 and 1000 kg in the case of spacecraft, and of more than 1000 kg for rocket upper stages. In the case of Cosmos-3M second stages, more than one object is located nearly in the same orbital plane. This provides the opportunity of multiremoval missions, more suitable for yearly removal rate and cost reduction needs. This paper deals with the feasibility study of a mission for the active removal of large abandoned objects in low Earth orbit. In particular, a mission is studied in which the removal of two Cosmos-3M second stages, that are numerous in low Earth orbit, is considered. The removal system relies on a Chaser spacecraft which performs rendezvous maneuvers with the two targets. The first Cosmos-3M stage is captured and an autonomous de-orbiting kit, carried by the Chaser, is attached to it. The de-orbiting kit consists of a Hybrid Propulsion Module, which is ignited to perform stage disposal and controlled reentry after Chaser separation. Then, the second Cosmos-3M stage is captured and, in this case, the primary propulsion system of the Chaser is used for the disposal of the mated configuration. Critical mission aspects and related technologies are investigated at a preliminary level. In particular, an innovative electro-adhesive system for target capture, mechanical systems for the hard docking with the target and a hybrid propulsion technology suitable for rendezvous, de-orbiting and controlled reentry operations are analyzed. This is performed on the basis of a preliminary mission profile, in which suitable rendezvous and disposal strategies have been considered and investigated by numerical analysis. A preliminary system mass budget is also performed, showing that the Chaser overall mass is about 1350 kg, including a primary propulsion system of about 300 kg, and a de-orbiting kit with a mass of about 200 kg. The system designed results suitable to be launched with VEGA, actually the cheapest European space launcher.
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