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Journal article
Open Access
A Local Lorentz invariance test with LAGEOS satellites
Lucchesi David, Visco Massimo, Peron Roberto, Rodriguez José C., Pucacco Giuseppe, Anselmo Luciano, Bassan Massimo, Appleby Graham, Cinelli Marco, Di Marco Alessandro, Lucente Marco, Magnafico Carmelo, Pardini Carmen, Sapio Feliciana
Strong theoretical arguments suggest that a breakdown of Lorentz Invariance could arise under some very particular conditions. From an experimental point of view, it is important to test the Local Lorentz Invariance with ever greater precision and in all contexts, regardless of the theoretical motivation for the possible violation. In this paper we discuss some aspects of the gravitational sector. Tests of Lorentz Invariance in the context of gravity are difficult and rare in the literature. Possible violations could arise from quantum physics applied to gravity or the presence of vector and tensor fields mediating the gravitational interaction together with the metric tensor of General Relativity. We present our results in the latter case. We analyzed the orbit of the LAGEOS and LAGEOS II satellites over a period of almost three decades. The effects of the possible preferred frame represented by the cosmic microwave background radiation on the mean argument of latitude of the satellites orbit were considered. These effects would manifest themselves mainly through the post-Newtonian parameter $α_1$, a parameter that has a null value in General Relativity. We constrain this parameterized post-Newtonian parameter down to the level of $α_1 \le 2\times10^{-5}$, improving a previous limit obtained through the Lunar Laser Ranging technique.Source: PHYSICAL REVIEW D
DOI: 10.1103/hj6p-bfyr
Metrics:
Lucchesi David, Visco Massimo, Peron Roberto, Rodriguez José C., Pucacco Giuseppe, Anselmo Luciano, Bassan Massimo, Appleby Graham, Cinelli Marco, Di Marco Alessandro, Lucente Marco, Magnafico Carmelo, Pardini Carmen, Sapio Feliciana
Strong theoretical arguments suggest that a breakdown of Lorentz Invariance could arise under some very particular conditions. From an experimental point of view, it is important to test the Local Lorentz Invariance with ever greater precision and in all contexts, regardless of the theoretical motivation for the possible violation. In this paper we discuss some aspects of the gravitational sector. Tests of Lorentz Invariance in the context of gravity are difficult and rare in the literature. Possible violations could arise from quantum physics applied to gravity or the presence of vector and tensor fields mediating the gravitational interaction together with the metric tensor of General Relativity. We present our results in the latter case. We analyzed the orbit of the LAGEOS and LAGEOS II satellites over a period of almost three decades. The effects of the possible preferred frame represented by the cosmic microwave background radiation on the mean argument of latitude of the satellites orbit were considered. These effects would manifest themselves mainly through the post-Newtonian parameter $α_1$, a parameter that has a null value in General Relativity. We constrain this parameterized post-Newtonian parameter down to the level of $α_1 \le 2\times10^{-5}$, improving a previous limit obtained through the Lunar Laser Ranging technique.Source: PHYSICAL REVIEW D
DOI: 10.1103/hj6p-bfyr
Metrics:
2026
Journal article
Open Access
The risk on the ground and in the airspace posed by uncontrolled re-entries: should the growth observed in recent years be considered worrying?
Pardini Carmen, Anselmo Luciano
Between 2010 and 2024, the risk posed by uncontrolled orbital re-entries of spacecraft, upper stages, and large debris to people on the ground and commercial aviation was assessed using realistic models for the number and casualty area of surviving fragments, as well as for the latitudinal distribution of population and air traffic. Each re-entered object was analyzed individually, taking into account its dry mass and actual orbital inclination. Furthermore, the effects of complete atmospheric demise were evaluated for objects with a re-entry dry mass of less than 300 kg. The nominal estimates obtained with the various approaches are expected to be affected by uncertainties of a factor of 2 or 3. Throughout the decade from 2010 to 2019, the risk levels remained relatively stable. However, from 2020 onward, there was a significant increase in risk, primarily due to the intensification of space activities. In 2024, the estimated collective casualty probability for people on the ground ranged between the nominal values of 5 % and 10 %, depending on the assumptions and models adopted. In the same year, the likelihood of a commercial aircraft being struck by re-entry debris capable of causing catastrophic failure was assessed to be between the nominal values of 3.7 × 10−5 and 1.5 × 10−4. This equates to an average of one aircraft impact every 27,000–6700 years, respectively. For passengers aboard commercial aircraft, the nominal collective casualty probability ranged from 0.44 % to 1.82 %. Although the overall re-entry risk remains relatively low, a notable upward trend was observed between 2019 and 2024. Specifically, the number of uncontrolled re-entries increased by a factor of 7, the cumulative re-entered mass increased by a factor of 3, the ground casualty probability rose by a factor of 3–4, and the casualty probability for commercial aircraft passengers increased by a factor of 3–6. This marked escalation highlights the urgent need for timely and effective mitigation strategies to prevent risks from exceeding thresholds deemed unacceptable from both operational and societal perspectives.Source: ACTA ASTRONAUTICA, vol. 242, pp. 312-327
DOI: 10.1016/j.actaastro.2026.01.049
Project(s): Space Debris and Sustainability of Long-Term Space Activities, Technical and Scientific Activities to Support CSSA/ISOC and Simulation of Sensor Architectures for SST
Metrics:
Pardini Carmen, Anselmo Luciano
Between 2010 and 2024, the risk posed by uncontrolled orbital re-entries of spacecraft, upper stages, and large debris to people on the ground and commercial aviation was assessed using realistic models for the number and casualty area of surviving fragments, as well as for the latitudinal distribution of population and air traffic. Each re-entered object was analyzed individually, taking into account its dry mass and actual orbital inclination. Furthermore, the effects of complete atmospheric demise were evaluated for objects with a re-entry dry mass of less than 300 kg. The nominal estimates obtained with the various approaches are expected to be affected by uncertainties of a factor of 2 or 3. Throughout the decade from 2010 to 2019, the risk levels remained relatively stable. However, from 2020 onward, there was a significant increase in risk, primarily due to the intensification of space activities. In 2024, the estimated collective casualty probability for people on the ground ranged between the nominal values of 5 % and 10 %, depending on the assumptions and models adopted. In the same year, the likelihood of a commercial aircraft being struck by re-entry debris capable of causing catastrophic failure was assessed to be between the nominal values of 3.7 × 10−5 and 1.5 × 10−4. This equates to an average of one aircraft impact every 27,000–6700 years, respectively. For passengers aboard commercial aircraft, the nominal collective casualty probability ranged from 0.44 % to 1.82 %. Although the overall re-entry risk remains relatively low, a notable upward trend was observed between 2019 and 2024. Specifically, the number of uncontrolled re-entries increased by a factor of 7, the cumulative re-entered mass increased by a factor of 3, the ground casualty probability rose by a factor of 3–4, and the casualty probability for commercial aircraft passengers increased by a factor of 3–6. This marked escalation highlights the urgent need for timely and effective mitigation strategies to prevent risks from exceeding thresholds deemed unacceptable from both operational and societal perspectives.Source: ACTA ASTRONAUTICA, vol. 242, pp. 312-327
DOI: 10.1016/j.actaastro.2026.01.049
Project(s): Space Debris and Sustainability of Long-Term Space Activities, Technical and Scientific Activities to Support CSSA/ISOC and Simulation of Sensor Architectures for SST
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CNR IRIS 
| www.sciencedirect.com | CNR IRIS 
2025
Journal article
Open Access
Orbital re-entries of human-made space objects: drawbacks for the upper atmosphere and the safety of people
Pardini C., Anselmo L.
The controlled and uncontrolled orbital re-entries occurred from 2010 to 2023 were reviewed. Excluding five Space Shuttle orbiters, the total mass re-entered into the atmosphere exceeded 4400 metric tons. In the five-year period 2019-2023, controlled re-entries accounted for nearly 62 % of the returned mass, including 31 % from Falcon 9 second stages alone, while uncontrolled re-entries of intact objects and large debris were responsible for the remaining 38 %. In 2023, the orbital re-entry mass dispersed as gas and particulate in the upper atmosphere was close to 600 metric tons. The ground casualty probability associated with the uncontrolled re-entry of satellites, orbital stages and large debris varied, on an annual basis, from 0.8 % in 2010 to 3.5 % in 2023, assuming the complete demise of all objects of less than 300 kg. In 2023, 70 % of the casualty probability was associated with orbital stages, 20 % with satellites and 10 % with large fragments.Source: JOURNAL OF SPACE SAFETY ENGINEERING, vol. 12 (issue 2), pp. 274-283
DOI: 10.1016/j.jsse.2025.04.009
Metrics:
Pardini C., Anselmo L.
The controlled and uncontrolled orbital re-entries occurred from 2010 to 2023 were reviewed. Excluding five Space Shuttle orbiters, the total mass re-entered into the atmosphere exceeded 4400 metric tons. In the five-year period 2019-2023, controlled re-entries accounted for nearly 62 % of the returned mass, including 31 % from Falcon 9 second stages alone, while uncontrolled re-entries of intact objects and large debris were responsible for the remaining 38 %. In 2023, the orbital re-entry mass dispersed as gas and particulate in the upper atmosphere was close to 600 metric tons. The ground casualty probability associated with the uncontrolled re-entry of satellites, orbital stages and large debris varied, on an annual basis, from 0.8 % in 2010 to 3.5 % in 2023, assuming the complete demise of all objects of less than 300 kg. In 2023, 70 % of the casualty probability was associated with orbital stages, 20 % with satellites and 10 % with large fragments.Source: JOURNAL OF SPACE SAFETY ENGINEERING, vol. 12 (issue 2), pp. 274-283
DOI: 10.1016/j.jsse.2025.04.009
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Journal of Space Safety Engineering | CNR IRIS | www.sciencedirect.com | CNR IRIS
2025
Conference article
Restricted
The risk on the ground and in the airspace posed by uncontrolled re-entries: should the growth observed in recent years be considered worrying?
Pardini C., Anselmo L.
Between 2010 and 2024, the risk posed by uncontrolled orbital re-entries of spacecraft, upper stages, and large debris to people on the ground and commercial aviation was assessed using realistic models for the number and casualty area of surviving fragments, as well as for the latitudinal distribution of population and air traffic. Each re-entered object was analyzed individually, taking into account its dry mass and actual orbital inclination. Furthermore, the effects of complete atmospheric demise were evaluated for objects with a re-entry dry mass of less than 300 kg. Throughout the decade from 2010 to 2019, the risk levels remained relatively stable. However, from 2020 onward, there was a significant increase in risk, primarily due to the intensification of space activities. In 2024, the estimated collective casualty probability for people on the ground ranged between 5% and 10%, depending on the assumptions and models adopted. In the same year, the likelihood of a commercial aircraft being struck by re-entry debris capable of causing catastrophic failure was assessed to be between 3.7×10E−5 and 1.5×10E−4. This equates to an average of one aircraft impact every 27,000 to 6700 years, respectively. For passengers aboard commercial aircraft, the estimated collective casualty probability ranged from 0.44% to 1.82%. Although the overall re-entry risk remains relatively low, a notable upward trend was observed between 2019 and 2024. Specifically, the number of uncontrolled re-entries increased by a factor of 7, the cumulative re-entered mass increased by a factor of 3, the ground casualty probability rose by a factor of 3 to 4, and the casualty probability for commercial aircraft passengers increased by a factor of 3 to 6. This marked escalation highlights the urgent need for timely and effective mitigation strategies to prevent risks from exceeding thresholds deemed unacceptable from both operational and societal perspectives.
Pardini C., Anselmo L.
Between 2010 and 2024, the risk posed by uncontrolled orbital re-entries of spacecraft, upper stages, and large debris to people on the ground and commercial aviation was assessed using realistic models for the number and casualty area of surviving fragments, as well as for the latitudinal distribution of population and air traffic. Each re-entered object was analyzed individually, taking into account its dry mass and actual orbital inclination. Furthermore, the effects of complete atmospheric demise were evaluated for objects with a re-entry dry mass of less than 300 kg. Throughout the decade from 2010 to 2019, the risk levels remained relatively stable. However, from 2020 onward, there was a significant increase in risk, primarily due to the intensification of space activities. In 2024, the estimated collective casualty probability for people on the ground ranged between 5% and 10%, depending on the assumptions and models adopted. In the same year, the likelihood of a commercial aircraft being struck by re-entry debris capable of causing catastrophic failure was assessed to be between 3.7×10E−5 and 1.5×10E−4. This equates to an average of one aircraft impact every 27,000 to 6700 years, respectively. For passengers aboard commercial aircraft, the estimated collective casualty probability ranged from 0.44% to 1.82%. Although the overall re-entry risk remains relatively low, a notable upward trend was observed between 2019 and 2024. Specifically, the number of uncontrolled re-entries increased by a factor of 7, the cumulative re-entered mass increased by a factor of 3, the ground casualty probability rose by a factor of 3 to 4, and the casualty probability for commercial aircraft passengers increased by a factor of 3 to 6. This marked escalation highlights the urgent need for timely and effective mitigation strategies to prevent risks from exceeding thresholds deemed unacceptable from both operational and societal perspectives.
See at:
dl.iafastro.directory | CNR IRIS | CNR IRIS
2025
Conference article
Open Access
Orbital debris in low earth orbit: how the situation has changed since the advent of mega-constellations
Anselmo L., Pardini C.
Despite the crude impression from looking superficially only at the total numbers, the situation in low Earth orbit has not deteriorated appreciably from late 2009 to early 2025, as far as orbital debris proper is concerned, even though satellite mega-constellations have appeared in the meantime, and the number of active spacecraft has increased tenfold. This is because mega-constellations have so far been handled appropriately, putting effective debris prevention and mitigation measures in place. But luck also played its part, as no serious accidents occurred, nor any catastrophic accidental collisions, which would have had more than a 50% chance of happening. The sensitivity of the low Earth orbit environment to sporadic single catastrophic events, as collisions involving abandoned spacecraft and upper stages, especially above 650 km, remains a pending threat that cannot be ignored. Therefore, a combination of adequate mitigation and remediation measures is needed to ensure smooth short-term operations in low Earth orbit and the long-term sustainability of space activities.
Anselmo L., Pardini C.
Despite the crude impression from looking superficially only at the total numbers, the situation in low Earth orbit has not deteriorated appreciably from late 2009 to early 2025, as far as orbital debris proper is concerned, even though satellite mega-constellations have appeared in the meantime, and the number of active spacecraft has increased tenfold. This is because mega-constellations have so far been handled appropriately, putting effective debris prevention and mitigation measures in place. But luck also played its part, as no serious accidents occurred, nor any catastrophic accidental collisions, which would have had more than a 50% chance of happening. The sensitivity of the low Earth orbit environment to sporadic single catastrophic events, as collisions involving abandoned spacecraft and upper stages, especially above 650 km, remains a pending threat that cannot be ignored. Therefore, a combination of adequate mitigation and remediation measures is needed to ensure smooth short-term operations in low Earth orbit and the long-term sustainability of space activities.
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conference.sdo.esoc.esa.int | CNR IRIS | CNR IRIS
2025
Conference article
Open Access
Casualty risk assessment of uncontrolled reentries after the deployment of the first large satellite constellations
Pardini C., Anselmo L.
From 2019 to 2024, the risk due to uncontrolled orbital reentries of spacecraft, upper stages, and large debris for people on the ground and commercial aircraft in flight was estimated using realistic models for the number and casualty area of the surviving fragments, and for the latitudinal distribution of population and planes in the air. Each reentered object was modeled independently, considering its correct orbital inclination. In addition, the effects of complete object demise below certain mass thresholds were also evaluated. Although the reentry risks are still relatively small, they have grown considerably from 2019 to 2024, mainly due to increased space activities. In 2024, the collective casualty probability for people on the ground was between 4.5% and 9.8%, while the individual annual casualty probability was not more than 10E−11. Always in 2024, the likelihood of aircraft being impacted by fragments capable of causing a catastrophic failure was between 3×10E−5 and 7×10E−5, corresponding, on average, to one airplane struck every 30,000 and 14,000 years, respectively. For commercial aircraft passengers, the collective casualty probability ranged from 0.42% to 0.84%, while the individual casualty probability was between 9×10E−13 and 2×10E−12.
Pardini C., Anselmo L.
From 2019 to 2024, the risk due to uncontrolled orbital reentries of spacecraft, upper stages, and large debris for people on the ground and commercial aircraft in flight was estimated using realistic models for the number and casualty area of the surviving fragments, and for the latitudinal distribution of population and planes in the air. Each reentered object was modeled independently, considering its correct orbital inclination. In addition, the effects of complete object demise below certain mass thresholds were also evaluated. Although the reentry risks are still relatively small, they have grown considerably from 2019 to 2024, mainly due to increased space activities. In 2024, the collective casualty probability for people on the ground was between 4.5% and 9.8%, while the individual annual casualty probability was not more than 10E−11. Always in 2024, the likelihood of aircraft being impacted by fragments capable of causing a catastrophic failure was between 3×10E−5 and 7×10E−5, corresponding, on average, to one airplane struck every 30,000 and 14,000 years, respectively. For commercial aircraft passengers, the collective casualty probability ranged from 0.42% to 0.84%, while the individual casualty probability was between 9×10E−13 and 2×10E−12.
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conference.sdo.esoc.esa.int | CNR IRIS | CNR IRIS
2024
Journal article
Open Access
The risk of casualties from the uncontrolled re-entry of spacecraft and orbital stages
Pardini C., Anselmo L.
From the beginning of 2010 to the end of 2022, 951 intact objects (spacecraft and orbital stages) with a radar cross-section greater than one square meter re-entered the Earth’s atmosphere uncontrolled. The total returned mass was about 1500 t, with a mean of 116 t per year, mostly concentrated (80 %) in orbital stages. On average, objects with a mass greater than 500 kg re-entered every 8 days, those exceeding 2000 kg every 2 weeks, and those above 5000 kg around 3 times per year. Only 4 % of the re-entries came from orbits with an eccentricity greater than 0.1, while 41 % were from nearly circular orbits with eccentricity lower than 0.001. 52 % of the re-entries occurred in the northern hemisphere and 48 % in the southern one. The areas of the planet most affected were those between 30° and 60° north. However, excluding the polar regions, the re-entry flux per unit area was relatively uniform, from 60° south to 60° north, implying a ground casualty risk mainly driven by the population density. 84 % of orbital stages and 19 % of spacecraft exceeded a casualty expectancy of 10−4, the ceiling recommended by several guidelines and standards worldwide. The total ground casualty expectancy over the 13 years analyzed was estimated to be 0.194, corresponding to a probability of injuring or killing at least one person of about 18 %. After remaining relatively stable from 2010 to 2018, the casualty expectancy and probability have grown systematically from then on, leading in 2022 to a chance of casualty of 2.9 %, with orbital stages and spacecraft contributing, respectively, 72 % and 28 %.Source: JOURNAL OF SPACE SAFETY ENGINEERING, vol. 11 (issue 2), pp. 181-191
DOI: 10.1016/j.jsse.2024.02.002
Metrics:
Pardini C., Anselmo L.
From the beginning of 2010 to the end of 2022, 951 intact objects (spacecraft and orbital stages) with a radar cross-section greater than one square meter re-entered the Earth’s atmosphere uncontrolled. The total returned mass was about 1500 t, with a mean of 116 t per year, mostly concentrated (80 %) in orbital stages. On average, objects with a mass greater than 500 kg re-entered every 8 days, those exceeding 2000 kg every 2 weeks, and those above 5000 kg around 3 times per year. Only 4 % of the re-entries came from orbits with an eccentricity greater than 0.1, while 41 % were from nearly circular orbits with eccentricity lower than 0.001. 52 % of the re-entries occurred in the northern hemisphere and 48 % in the southern one. The areas of the planet most affected were those between 30° and 60° north. However, excluding the polar regions, the re-entry flux per unit area was relatively uniform, from 60° south to 60° north, implying a ground casualty risk mainly driven by the population density. 84 % of orbital stages and 19 % of spacecraft exceeded a casualty expectancy of 10−4, the ceiling recommended by several guidelines and standards worldwide. The total ground casualty expectancy over the 13 years analyzed was estimated to be 0.194, corresponding to a probability of injuring or killing at least one person of about 18 %. After remaining relatively stable from 2010 to 2018, the casualty expectancy and probability have grown systematically from then on, leading in 2022 to a chance of casualty of 2.9 %, with orbital stages and spacecraft contributing, respectively, 72 % and 28 %.Source: JOURNAL OF SPACE SAFETY ENGINEERING, vol. 11 (issue 2), pp. 181-191
DOI: 10.1016/j.jsse.2024.02.002
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2024
Journal article
Open Access
On the need to assess and mitigate the risk from uncontrolled re-entries of artificial space objects in view of the current and future developments in space activities
Pardini C., Anselmo L.
From 1 January 2010 to 24 August 2023, 566 orbital stages and 511 spacecraft with a radar cross section >1 m2 have re-entered without control the Earth’s atmosphere. The total returned mass was 1650 metric tons, corresponding to a mean of 115 metric tons per year. 77% of the mass belonged to orbital stages, 23% to spacecraft. The uncontrolled re-entries of orbital stages are currently dominated by China, accounting for more than half of the decaying mass, while for spacecraft 2/3 of the mass belongs to American satellites. 60% of the re-entries occurred within 2 years of the launch. The ground casualty expectancy due to orbital stages was always predominant over that from spacecraft, by an average factor of nearly three. From 2010 to 2018, the total casualty probability remained substantially stable, with a mean annual value just over 1%. Since 2019, instead, the annual casualty probability of both spacecraft and orbital stages progressively increased, reaching a total value of around 3% in 2022 and 2023 (extrapolated). Even assuming a stable launch activity, in the coming years, when many of the recently launched spacecraft will start to re-enter, the casualty expectancy of orbital stages will remain basically the same, while that of spacecraft might progressively increase by a factor of 20. This would lead to an annual casualty probability of about 20%, even more in case of a further growth in launch activity, very likely based on current forecasts. The quick implementation of widespread and effective mitigation measures, like controlled de-orbiting and design for demise, is therefore necessary, to prevent the situation from deteriorating too much.Source: ACTA ASTRONAUTICA, vol. 219, pp. 662-669
DOI: 10.1016/j.actaastro.2024.03.057
Metrics:
Pardini C., Anselmo L.
From 1 January 2010 to 24 August 2023, 566 orbital stages and 511 spacecraft with a radar cross section >1 m2 have re-entered without control the Earth’s atmosphere. The total returned mass was 1650 metric tons, corresponding to a mean of 115 metric tons per year. 77% of the mass belonged to orbital stages, 23% to spacecraft. The uncontrolled re-entries of orbital stages are currently dominated by China, accounting for more than half of the decaying mass, while for spacecraft 2/3 of the mass belongs to American satellites. 60% of the re-entries occurred within 2 years of the launch. The ground casualty expectancy due to orbital stages was always predominant over that from spacecraft, by an average factor of nearly three. From 2010 to 2018, the total casualty probability remained substantially stable, with a mean annual value just over 1%. Since 2019, instead, the annual casualty probability of both spacecraft and orbital stages progressively increased, reaching a total value of around 3% in 2022 and 2023 (extrapolated). Even assuming a stable launch activity, in the coming years, when many of the recently launched spacecraft will start to re-enter, the casualty expectancy of orbital stages will remain basically the same, while that of spacecraft might progressively increase by a factor of 20. This would lead to an annual casualty probability of about 20%, even more in case of a further growth in launch activity, very likely based on current forecasts. The quick implementation of widespread and effective mitigation measures, like controlled de-orbiting and design for demise, is therefore necessary, to prevent the situation from deteriorating too much.Source: ACTA ASTRONAUTICA, vol. 219, pp. 662-669
DOI: 10.1016/j.actaastro.2024.03.057
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2024
Conference article
Restricted
Orbital re-entries of human-made space objects: drawbacks for the upper atmosphere and the safety of people
Pardini C., Anselmo L.
The controlled and uncontrolled orbital re-entries occurred from 2010 to 2023 were reviewed. Excluding five Space Shuttle orbiters, the total mass re-entered into the atmosphere exceeded 4200 metric tons. In the five-year period 2019-2023, controlled spacecraft re-entries accounted for nearly 20% of the returned mass, against 45% associated with uncontrolled re-entries of intact objects and large debris, and 35% with controlled re-entries of Falcon 9 second stages. In 2023, the orbital re-entry mass dispersed as gas and particulate in the upper atmosphere was close to 600 metric tons. The ground casualty probability associated with the uncontrolled re-entry of satellites, orbital stages and large debris varied, on an annual basis, from 0.8% in 2010 to 3.5% in 2023, assuming the complete demise of all objects of less than 300 kg. Always in 2023, 70% of the casualty probability was associated with orbital stages, 20% with satellites and 10% with large fragments.
Pardini C., Anselmo L.
The controlled and uncontrolled orbital re-entries occurred from 2010 to 2023 were reviewed. Excluding five Space Shuttle orbiters, the total mass re-entered into the atmosphere exceeded 4200 metric tons. In the five-year period 2019-2023, controlled spacecraft re-entries accounted for nearly 20% of the returned mass, against 45% associated with uncontrolled re-entries of intact objects and large debris, and 35% with controlled re-entries of Falcon 9 second stages. In 2023, the orbital re-entry mass dispersed as gas and particulate in the upper atmosphere was close to 600 metric tons. The ground casualty probability associated with the uncontrolled re-entry of satellites, orbital stages and large debris varied, on an annual basis, from 0.8% in 2010 to 3.5% in 2023, assuming the complete demise of all objects of less than 300 kg. Always in 2023, 70% of the casualty probability was associated with orbital stages, 20% with satellites and 10% with large fragments.
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CNR IRIS | CNR IRIS | www.iaass.org
2023
Journal article
Open Access
The short-term effects of the Cosmos 1408 fragmentation on neighboring inhabited space stations and large constellations
Pardini C, Anselmo L
In terms of cataloged debris produced, the anti-satellite test carried out by Russia, in November 2021, at an altitude of about 480 km, leading to the destruction of the old satellite Cosmos 1408, was the second worst to date and represented the third worst fragmentation in orbit. It generated more than 1/4 of the cataloged debris produced over 55 years by all such tests and almost twice as many as were produced by all previous Soviet tests. After placing this event in its historical context, this paper analyzes in detail how the evolution of the Cosmos 1408 debris cloud affected the environment below 600 km in the first seven months, focusing on the two operational space stations and the Starlink large constellation of satellites. During the first six months following the test, the Cosmos 1408 cloud of fragments nearly doubled the average flux of cataloged objects on the International Space Station and increased by about 3/4 that on China's Tiangong. In the same period, the Starlink large constellation saw an average increase in the flux of cataloged objects of about 20%. Some orbital planes, the "counter-rotating" ones with respect to the Cosmos 1408 debris cloud, were more affected than others, and the affected planes gradually changed over time, due to the differential precession of cloud and constellation nodes. However, being the Starlink constellation 70 km higher up, the flux of Cosmos 1408 cataloged debris steadily decreased over the period analyzed, due to the cloud orbital decay, reducing to just over a quarter of its extrapolated initial value after seven months.Source: ACTA ASTRONAUTICA
DOI: 10.1016/j.actaastro.2023.02.043
Metrics:
Pardini C, Anselmo L
In terms of cataloged debris produced, the anti-satellite test carried out by Russia, in November 2021, at an altitude of about 480 km, leading to the destruction of the old satellite Cosmos 1408, was the second worst to date and represented the third worst fragmentation in orbit. It generated more than 1/4 of the cataloged debris produced over 55 years by all such tests and almost twice as many as were produced by all previous Soviet tests. After placing this event in its historical context, this paper analyzes in detail how the evolution of the Cosmos 1408 debris cloud affected the environment below 600 km in the first seven months, focusing on the two operational space stations and the Starlink large constellation of satellites. During the first six months following the test, the Cosmos 1408 cloud of fragments nearly doubled the average flux of cataloged objects on the International Space Station and increased by about 3/4 that on China's Tiangong. In the same period, the Starlink large constellation saw an average increase in the flux of cataloged objects of about 20%. Some orbital planes, the "counter-rotating" ones with respect to the Cosmos 1408 debris cloud, were more affected than others, and the affected planes gradually changed over time, due to the differential precession of cloud and constellation nodes. However, being the Starlink constellation 70 km higher up, the flux of Cosmos 1408 cataloged debris steadily decreased over the period analyzed, due to the cloud orbital decay, reducing to just over a quarter of its extrapolated initial value after seven months.Source: ACTA ASTRONAUTICA
DOI: 10.1016/j.actaastro.2023.02.043
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CNR IRIS | ISTI Repository | www.sciencedirect.com | CNR IRIS
2023
Conference article
Open Access
On the need to assess and mitigate the risk from uncontrolled re-entries of artificial space objects in view of the current and future developments in space activities
Pardini C, Anselmo L
From 1 January 2010 to 24 August 2023, 566 orbital stages and 511 spacecraft with a radar cross section > 1 m2 have re-entered without control the Earth's atmosphere. The total returned mass was 1650 metric tons, corresponding to a mean of 115 metric tons per year. 77% of the mass belonged to orbital stages, 23% to spacecraft. The uncontrolled re-entries of orbital stages are currently dominated by China, accounting for more than half of the decaying mass, while for spacecraft 2/3 of the mass belongs to American satellites. 60% of the re-entries occurred within 2 years of the launch. The ground casualty expectancy due to orbital stages was always predominant over that from spacecraft, by an average factor of nearly three. From 2010 to 2018, the total casualty probability remained substantially stable, with a mean annual value just over 1%. Since 2019, instead, the annual casualty probability of both spacecraft and orbital stages progressively increased, reaching a total value of around 3% in 2022 and 2023 (extrapolated). Even assuming a stable launch activity, in the coming years, when many of the recently launched spacecraft will start to re-enter, the casualty expectancy of orbital stages will remain basically the same, while that of spacecraft might progressively increase by a factor of 20. This would lead to an annual casualty probability of about 20%, even more in case of a further growth in launch activity, very likely based on current forecasts. The quick implementation of widespread and effective mitigation measures, like controlled de-orbiting and design for demise, is therefore necessary, to prevent the situation from deteriorating too much.
Pardini C, Anselmo L
From 1 January 2010 to 24 August 2023, 566 orbital stages and 511 spacecraft with a radar cross section > 1 m2 have re-entered without control the Earth's atmosphere. The total returned mass was 1650 metric tons, corresponding to a mean of 115 metric tons per year. 77% of the mass belonged to orbital stages, 23% to spacecraft. The uncontrolled re-entries of orbital stages are currently dominated by China, accounting for more than half of the decaying mass, while for spacecraft 2/3 of the mass belongs to American satellites. 60% of the re-entries occurred within 2 years of the launch. The ground casualty expectancy due to orbital stages was always predominant over that from spacecraft, by an average factor of nearly three. From 2010 to 2018, the total casualty probability remained substantially stable, with a mean annual value just over 1%. Since 2019, instead, the annual casualty probability of both spacecraft and orbital stages progressively increased, reaching a total value of around 3% in 2022 and 2023 (extrapolated). Even assuming a stable launch activity, in the coming years, when many of the recently launched spacecraft will start to re-enter, the casualty expectancy of orbital stages will remain basically the same, while that of spacecraft might progressively increase by a factor of 20. This would lead to an annual casualty probability of about 20%, even more in case of a further growth in launch activity, very likely based on current forecasts. The quick implementation of widespread and effective mitigation measures, like controlled de-orbiting and design for demise, is therefore necessary, to prevent the situation from deteriorating too much.
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CNR IRIS | ISTI Repository | www.iafastro.org | CNR IRIS
2023
Other
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Disposal of high inclination geosynchronous spacecraft and orbital stages
Anselmo L
At the end of its 35th meeting in Darmstadt, in 2017, the WG4 proposed - at the request of CNES - a new AI on Disposal of High Inclination Geosynchronous Spacecraft and Orbital Stages. The SG discussed the proposal at the intermediate meeting held in Adelaide during the IAC-2017 conference. There, several delegations asked for changes and further clarifications. At the 36th IADC plenary meeting, held in Tsukuba in 2018, ASI made two technical presentations addressing the class of objects in geosynchronous orbits for which the IADC re-orbiting formula is not able to prevent the later crossing of the GEO protected region. After the meeting, the WG4 modified the wording and resubmitted the AI to the SG on 13 September 2018. It was discussed at the SG intermediate meeting held in Bremen during the IAC-2018 conference (3 October 2018), but no decision was taken. On 10 December 2018, the SG approved the proposal as AI 36.3, stressing that «updating guidelines should not be a direct output of the action item». As part of the wrap-up work on AI 32.1 Update of the IADC Space Debris Mitigation Guidelines and of the Support Document (On-ground Casualty Expectation and Max Long Term Presence in GEO) during 2020 and early 2021, it was noted that there are similarities between the long-term presence of spacecraft and upper stages on orbits crossing the GEO protected region. Such crossing orbits include (super-)GTO's as well as highly eccentric orbits. Noting that also AI 22.2 failed to find consensus on the topic of limiting the long-term presence in GEO, the lessons learned are put in context in this report as well.
Anselmo L
At the end of its 35th meeting in Darmstadt, in 2017, the WG4 proposed - at the request of CNES - a new AI on Disposal of High Inclination Geosynchronous Spacecraft and Orbital Stages. The SG discussed the proposal at the intermediate meeting held in Adelaide during the IAC-2017 conference. There, several delegations asked for changes and further clarifications. At the 36th IADC plenary meeting, held in Tsukuba in 2018, ASI made two technical presentations addressing the class of objects in geosynchronous orbits for which the IADC re-orbiting formula is not able to prevent the later crossing of the GEO protected region. After the meeting, the WG4 modified the wording and resubmitted the AI to the SG on 13 September 2018. It was discussed at the SG intermediate meeting held in Bremen during the IAC-2018 conference (3 October 2018), but no decision was taken. On 10 December 2018, the SG approved the proposal as AI 36.3, stressing that «updating guidelines should not be a direct output of the action item». As part of the wrap-up work on AI 32.1 Update of the IADC Space Debris Mitigation Guidelines and of the Support Document (On-ground Casualty Expectation and Max Long Term Presence in GEO) during 2020 and early 2021, it was noted that there are similarities between the long-term presence of spacecraft and upper stages on orbits crossing the GEO protected region. Such crossing orbits include (super-)GTO's as well as highly eccentric orbits. Noting that also AI 22.2 failed to find consensus on the topic of limiting the long-term presence in GEO, the lessons learned are put in context in this report as well.
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2023
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Accordo di collaborazione tra ASI e INAF N. 2020-6-HH.0, Deliverable Document RF_2019-2021 - Detriti spaziali supporto alle attività IADC e SST 2019-2021
Bianchi G, Teofilatto P, Piergentili F, Valentini G, Buzzoni A, Di Lizia P, Colombo C, Rossi A, Pardini C, Francesconi A, Anselmo L
Questo documento è l'ultimo deliverable dell'accordo di collaborazione tra ASI e INAF in ambito "Detriti Spaziali- Supporto alle attività IADC e SST 2019-2021". Sono riportate le attività svolte, dai vari enti coinvolti, dal M31 al M38, suddivisi per WP (Work Package).
Bianchi G, Teofilatto P, Piergentili F, Valentini G, Buzzoni A, Di Lizia P, Colombo C, Rossi A, Pardini C, Francesconi A, Anselmo L
Questo documento è l'ultimo deliverable dell'accordo di collaborazione tra ASI e INAF in ambito "Detriti Spaziali- Supporto alle attività IADC e SST 2019-2021". Sono riportate le attività svolte, dai vari enti coinvolti, dal M31 al M38, suddivisi per WP (Work Package).
2023
Other
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Uncontrolled re-entries: the need to mitigate the increasing risk on ground due to the re-entry of large spacecraft and orbital stages, and to establish an aggregate re-entry risk for constellations
Pardini C, Anselmo L
The casualty probability associated with the uncontrolled re-entry of spacecraft is still quite low, of the order of 0.8% in 2022, but the disposal of satellites from the current planned mega-constellations could significantly increase the likelihood of casualties on the ground in the coming years. In fact, even if the value of the casualty expectancy associated with each satellite of a constellation is below the alert threshold of 10-4, if several thousands more satellites were to re-enter without control every year, the casualty probability would probably reach unacceptable values for safety on the ground and in the airspace. Therefore, it would be necessary to establish an aggregate re-entry risk for constellations, by adopting, for instance, an annual limit for the casualty expectancy value that the constellation shall not exceed.
Pardini C, Anselmo L
The casualty probability associated with the uncontrolled re-entry of spacecraft is still quite low, of the order of 0.8% in 2022, but the disposal of satellites from the current planned mega-constellations could significantly increase the likelihood of casualties on the ground in the coming years. In fact, even if the value of the casualty expectancy associated with each satellite of a constellation is below the alert threshold of 10-4, if several thousands more satellites were to re-enter without control every year, the casualty probability would probably reach unacceptable values for safety on the ground and in the airspace. Therefore, it would be necessary to establish an aggregate re-entry risk for constellations, by adopting, for instance, an annual limit for the casualty expectancy value that the constellation shall not exceed.
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2023
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Italian Space Agency space debris mitigation activities - Delegation report
Vellutini E, Anselmo L
Statistics from IADC-40 (Oct 2022) to IADC-41 (Jun 2023).
Vellutini E, Anselmo L
Statistics from IADC-40 (Oct 2022) to IADC-41 (Jun 2023).
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2023
Conference article
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The risk of casualties from the uncontrolled re-entry of spacecraft and orbital stages
Pardini C, Anselmo L
From the beginning of 2010 to the end of 2022, 951 intact objects (spacecraft and orbital stages) with a radar cross-section greater than one square meter re-entered the Earth's atmosphere uncontrolled. The total returned mass was about 1500 metric tons, with a mean of 116 metric tons per year, mostly concentrated (80%) in orbital stages. On average, objects with a mass greater than 500 kg re-entered every 8 days, those exceeding 2000 kg every 2 weeks, and those above 5000 kg around 3 times per year. Only 4% of the re-entries came from orbits with an eccentricity greater than 0.1, while 41% were from nearly circular orbits with eccentricity lower than 0.001. 52% of the re-entries occurred in the northern hemisphere and 48% in the southern one. The areas of the planet most affected where those between 30 deg and 60 deg north. However, excluding the polar regions, the re-entry flux per unit area was relatively uniform, from 60° south to 60° north, implying a ground casualty risk manly driven by the population density. 84% of orbital stages and 19% of spacecraft exceeded a casualty expectancy of 10-4, the ceiling recommended by several guidelines and standards worldwide. The total ground casualty expectancy over the 13 years analyzed was estimated to be 0.194, corresponding to a probability of injuring or killing at least one person of about 18%. After remaining relatively stable from 2010 to 2018, the casualty expectancy and probability have grown systematically from then on, leading in 2022 to a chance of casualty of 2.9%, with orbital stages and spacecraft contributing, respectively, 72% and 28%.
Pardini C, Anselmo L
From the beginning of 2010 to the end of 2022, 951 intact objects (spacecraft and orbital stages) with a radar cross-section greater than one square meter re-entered the Earth's atmosphere uncontrolled. The total returned mass was about 1500 metric tons, with a mean of 116 metric tons per year, mostly concentrated (80%) in orbital stages. On average, objects with a mass greater than 500 kg re-entered every 8 days, those exceeding 2000 kg every 2 weeks, and those above 5000 kg around 3 times per year. Only 4% of the re-entries came from orbits with an eccentricity greater than 0.1, while 41% were from nearly circular orbits with eccentricity lower than 0.001. 52% of the re-entries occurred in the northern hemisphere and 48% in the southern one. The areas of the planet most affected where those between 30 deg and 60 deg north. However, excluding the polar regions, the re-entry flux per unit area was relatively uniform, from 60° south to 60° north, implying a ground casualty risk manly driven by the population density. 84% of orbital stages and 19% of spacecraft exceeded a casualty expectancy of 10-4, the ceiling recommended by several guidelines and standards worldwide. The total ground casualty expectancy over the 13 years analyzed was estimated to be 0.194, corresponding to a probability of injuring or killing at least one person of about 18%. After remaining relatively stable from 2010 to 2018, the casualty expectancy and probability have grown systematically from then on, leading in 2022 to a chance of casualty of 2.9%, with orbital stages and spacecraft contributing, respectively, 72% and 28%.
2023
Other
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METRIC: a mission concept for upper atmosphere mapping, gravitational physics and geodesy
Peron R, Lorenzini Ec, Anselmo L, Bassan M, Bianco G, Dell'Agnello S, Iafolla V, Lefevre C, Lucchesi Dm, Lucente M, Magnafico C, Muccino M, Negusini M, Pardini C, Porcelli L, Santoli F, Tornatore V, Valmorbida A, Vecchiato A, Vespe F
We describe here a mission concept - called METRIC (Measurement of EnvironmenTal and Relativistic In-orbit preCessions) - for a spacecraft to be placed in a low Earth orbit, with dedicated instrumentation to provide data useful for atmospheric science, fundamental physics and geodesy. The main scientific objectives are: map the atmospheric density by in-situ acceleration measurement and by spacecraft tracking at altitudes of great interest for satellites deorbiting; perform fundamental physics tests through a precise orbit determination and verification of the equation of motion for a well-characterized test mass; provide an additional, space-based, node to improve the tie among different space geodesy techniques. These three areas being distinct but strongly interrelated in the case of Earth System science, it appears that they can benefit from the availability of a well-calibrated space-based platform such as the one being proposed. Following a discussion of the scientific objectives, the mission idea will be described with a baseline for spacecraft configuration, scientific instruments and data analysis strategies.
Peron R, Lorenzini Ec, Anselmo L, Bassan M, Bianco G, Dell'Agnello S, Iafolla V, Lefevre C, Lucchesi Dm, Lucente M, Magnafico C, Muccino M, Negusini M, Pardini C, Porcelli L, Santoli F, Tornatore V, Valmorbida A, Vecchiato A, Vespe F
We describe here a mission concept - called METRIC (Measurement of EnvironmenTal and Relativistic In-orbit preCessions) - for a spacecraft to be placed in a low Earth orbit, with dedicated instrumentation to provide data useful for atmospheric science, fundamental physics and geodesy. The main scientific objectives are: map the atmospheric density by in-situ acceleration measurement and by spacecraft tracking at altitudes of great interest for satellites deorbiting; perform fundamental physics tests through a precise orbit determination and verification of the equation of motion for a well-characterized test mass; provide an additional, space-based, node to improve the tie among different space geodesy techniques. These three areas being distinct but strongly interrelated in the case of Earth System science, it appears that they can benefit from the availability of a well-calibrated space-based platform such as the one being proposed. Following a discussion of the scientific objectives, the mission idea will be described with a baseline for spacecraft configuration, scientific instruments and data analysis strategies.
2022
Journal article
Open Access
Effects of the deployment and disposal of mega-constellations on human spaceflight operations in low LEO
Pardini C, Anselmo L
The substantial space traffic changes occurred since the 2010s are having measurable repercussions even at the altitudes used for human spaceflight. These changes were mainly driven by the deployment of thousands of small satellites and cubesats below 600 km. After having evaluated how the situation evolved, from 2008 to 2021, at the altitudes of the International and Chinese space stations, and discussed the main aspects of the problem that may have an operational impact, the attention was focused on what might be expected in the 2020s, whether the current deployment plans for mega-constellations will be realized in whole or in part. Finally, the rationale for the introduction of a "human spaceflight protected region", with the associated space traffic management recommendations, is presented and discussed.Source: JOURNAL OF SPACE SAFETY ENGINEERING, vol. 9 (issue 2), pp. 274-279
DOI: 10.1016/j.jsse.2022.03.001
Metrics:
Pardini C, Anselmo L
The substantial space traffic changes occurred since the 2010s are having measurable repercussions even at the altitudes used for human spaceflight. These changes were mainly driven by the deployment of thousands of small satellites and cubesats below 600 km. After having evaluated how the situation evolved, from 2008 to 2021, at the altitudes of the International and Chinese space stations, and discussed the main aspects of the problem that may have an operational impact, the attention was focused on what might be expected in the 2020s, whether the current deployment plans for mega-constellations will be realized in whole or in part. Finally, the rationale for the introduction of a "human spaceflight protected region", with the associated space traffic management recommendations, is presented and discussed.Source: JOURNAL OF SPACE SAFETY ENGINEERING, vol. 9 (issue 2), pp. 274-279
DOI: 10.1016/j.jsse.2022.03.001
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Journal of Space Safety Engineering | CNR IRIS | ISTI Repository | www.sciencedirect.com | CNR IRIS
2022
Journal article
Open Access
The Kinetic casualty risk of uncontrolled re-entries before and after the transition to small satellites and mega-constellations
Pardini C, Anselmo L
Over the last 11 years (2010-2020), more than 600 intact objects larger than 1 m^2 have re-entered without control into the Earth's atmosphere. The total returned mass was approximately 1100 t, roughly corresponding to the re-entry of nearly 100 t per year, mostly concentrated (79%) in rocket bodies. Objects with a mass greater than 500 kg re-entered every about 8 days, those exceeding 2000 kg every about 2 weeks and those heavier than 5000 kg one or twice per year. The total casualty expectancy associated with uncontrolled re-entries over the past 11 years was of the order of 1.4 × 10^-1, that in 2020 was almost 1.7 × 10^-2, corresponding to a probability of having had at least one victim of approximately 13% and 2%, respectively. Unlike the alert threshold of 10^-4, linked to single re-entry events, no cumulative risk limit exists for satellite re-entries over one year or more. However, the casualty probability, although still relatively small, cannot be considered negligible, even in view of the launches of mega-constellations planned in the coming years. For instance, if no design for demise was implemented, the addition of 4000 spacecraft re-entering annually would increase the probability of having at least one victim to nearly 30% per year, while 20,000 more satellites would boost it to almost 80%.Source: JOURNAL OF SPACE SAFETY ENGINEERING, vol. 9 (issue 3), pp. 414-426
DOI: 10.1016/j.jsse.2022.04.003
Metrics:
Pardini C, Anselmo L
Over the last 11 years (2010-2020), more than 600 intact objects larger than 1 m^2 have re-entered without control into the Earth's atmosphere. The total returned mass was approximately 1100 t, roughly corresponding to the re-entry of nearly 100 t per year, mostly concentrated (79%) in rocket bodies. Objects with a mass greater than 500 kg re-entered every about 8 days, those exceeding 2000 kg every about 2 weeks and those heavier than 5000 kg one or twice per year. The total casualty expectancy associated with uncontrolled re-entries over the past 11 years was of the order of 1.4 × 10^-1, that in 2020 was almost 1.7 × 10^-2, corresponding to a probability of having had at least one victim of approximately 13% and 2%, respectively. Unlike the alert threshold of 10^-4, linked to single re-entry events, no cumulative risk limit exists for satellite re-entries over one year or more. However, the casualty probability, although still relatively small, cannot be considered negligible, even in view of the launches of mega-constellations planned in the coming years. For instance, if no design for demise was implemented, the addition of 4000 spacecraft re-entering annually would increase the probability of having at least one victim to nearly 30% per year, while 20,000 more satellites would boost it to almost 80%.Source: JOURNAL OF SPACE SAFETY ENGINEERING, vol. 9 (issue 3), pp. 414-426
DOI: 10.1016/j.jsse.2022.04.003
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Journal of Space Safety Engineering | CNR IRIS | ISTI Repository | www.sciencedirect.com | CNR IRIS
2022
Journal article
Open Access
Using the space debris flux to assess the criticality of the environment in low Earth orbit
Pardini C, Anselmo L
In this paper we introduce a new index for evaluating the likelihood of accidental collisions leading to the complete destruction of intact objects in a volume of space in low Earth orbit (LEO). The proposed index is therefore not intended to assess the criticality of individual objects or missions, but rather to estimate the global impact of space activities on a given region of space. Moreover, the new index has been designed to be objective, as simple as possible, built from easily accessible data, as well as smoothly reproducible by third parties. Named "volumetric collision rate index", it has been developed starting from analytical equations expressing the collision rate as a function of the fluxes of intact objects and cataloged debris pieces. The application of reasonable simplifying assumptions and approximations has finally made it possible to define a dimensionless index that explicitly depends only on the spatial densities of intact objects and cataloged debris pieces. It has therefore been applied to the LEO environment, analyzing its evolution from mid-2008 to mid-2020, a crucial period characterized by an impressive change of space activity patterns, with the launch of lots of small satellites and mega-constellations. We also discuss how the index can be further improved, taking into account the maneuverable satellites, which do not contribute to the collision rate, and the increasing number of cubesats, which in many respects are more similar to debris, finally presenting a preliminary analysis in this direction.Source: ACTA ASTRONAUTICA, vol. 198, pp. 756-760
DOI: 10.1016/j.actaastro.2022.05.045
Metrics:
Pardini C, Anselmo L
In this paper we introduce a new index for evaluating the likelihood of accidental collisions leading to the complete destruction of intact objects in a volume of space in low Earth orbit (LEO). The proposed index is therefore not intended to assess the criticality of individual objects or missions, but rather to estimate the global impact of space activities on a given region of space. Moreover, the new index has been designed to be objective, as simple as possible, built from easily accessible data, as well as smoothly reproducible by third parties. Named "volumetric collision rate index", it has been developed starting from analytical equations expressing the collision rate as a function of the fluxes of intact objects and cataloged debris pieces. The application of reasonable simplifying assumptions and approximations has finally made it possible to define a dimensionless index that explicitly depends only on the spatial densities of intact objects and cataloged debris pieces. It has therefore been applied to the LEO environment, analyzing its evolution from mid-2008 to mid-2020, a crucial period characterized by an impressive change of space activity patterns, with the launch of lots of small satellites and mega-constellations. We also discuss how the index can be further improved, taking into account the maneuverable satellites, which do not contribute to the collision rate, and the increasing number of cubesats, which in many respects are more similar to debris, finally presenting a preliminary analysis in this direction.Source: ACTA ASTRONAUTICA, vol. 198, pp. 756-760
DOI: 10.1016/j.actaastro.2022.05.045
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Acta Astronautica | CNR IRIS | ISTI Repository | www.sciencedirect.com | CNR IRIS