ESA’s process for the identification and assessment of high-risk conjunction events

Flohrer, Tim; Krag, H.; Klinkrad, H.

doi:10.1016/j.asr.2009.04.012

Cited by 32 publications

(19 citation statements)

References 7 publications

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“…will have much higher collision probabilities than most others throughout the entire mission will occur, however. Such extremely dangerous conjunctions are normally avoided during spacecraft operations by postponing the manoeuvres or even conducting dedicated collision avoidance (Flohrer et al, 2009). Not every proposed ADR architecture provides such control, however.…”

Section: Resultsmentioning

confidence: 99%

“…This means that the set of exemplar conjunction geometries found with the TLE catalogue snapshots provided a corresponding set of exemplar collision probabilities and the events with high collision probability were as infrequent as the ones with very low miss distance. Such high collision probability conjunctions do take place when using higher fidelity ephemerides and algorithms, which leads to conjunction screenings being routinely performed for operational spacecraft (Flohrer et al, 2009). The existence of such events is not an artefact resulting from the ephemerides or the assumed object sizes, for example.…”

Section: Discussionmentioning

confidence: 99%

“…However, these analyses used long-term collision probability estimation techniques, which do not reflect the trends in collision probabilities that will be seen during operational collision screenings. This paper estimates probabilities of causing orbital collisions that are associated with various proposed ADR approaches using algorithms similar to those used operationally (Flohrer et al, 2009). Only ADR mission trajectories, not technologies, are analysed.…”

Section: Introductionmentioning

confidence: 99%

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Considering the collision probability of Active Debris Removal missions

et al. 2017

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Active Debris Removal (ADR) methods are being developed due to a growing concern about the congestion on-orbit and sustainability of spaceflight. This study examined the probability of an on-orbit collision between an ADR target, whilst being de-orbited, and all the objects in the public catalogue published by the US Strategic Command. Such a collision could have significant effects because the target is likely to be located in a densely populated orbital regime and thus follow-on collisions could take place. Six impulsive and three low-thrust example ADR mission trajectories were screened for conjunctions. Extremely close conjunctions were found to result in as much as 99% of the total accumulated collision probability. The need to avoid those conjunctions is highlighted, which raises concerns about ADR methods that do not support collision avoidance. Shortening the removal missions, at an expense of more ∆V and so cost, will also lower their collision probability by reducing the number of conjunctions that they will experience.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Considering the collision probability of Active Debris Removal missions

et al. 2017

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“…Today, CRASS is used as a central element of the operational collision avoidance process at ESOC 9 . It is, however, not foreseen that the satellite operators themselves will interact with the CRASS system.…”

Section: The Collision Risk Assessment Tool (Crass)mentioning

confidence: 99%

Conjunction Evolutions: The Process of Adapting and Evolving Operational Collision Warning Software from Server to Service Oriented Architecture

Fletcher¹,

Navarro²,

Martín³

et al. 2012

SpaceOps 2012 Conference

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In 2002, the European Space Agency developed the first generation of conjunction warning tools in order to provide alerts and warnings for operational ESA satellites. Through numerous developments since the initial delivery, this tool became a fundamental part of the operational process for all ESA spacecraft. With the advent of the European Space Surveillance precursor programme, it was seen that the original software would have to be reengineered in order to improve dynamic services to customers outside of ESA. As a result, the first phase of the space surveillance and tracking segment to provide pre-operational services adapted the original software by providing a modern web-based front-end to the core software, hence retaining the original core algorithms but improving the interaction with the end user. This process also identified various requirements to modify the core software in order to comply with the SSA mission requirements. This was performed in phase two of the pre-operational services by dramatically improving the scope and capabilities of the core software as well as providing the ability to form part of a service oriented architecture. This paper will describe and investigate the steps taken in this development journey and the lessons learnt on the way.

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“…The operational service for the assessment of collision risks of ESA satellites is based on the collision risk assessment software CRASS and the orbit determination software ODIN (Flohrer et al, 2009a). A daily automated screening is performed to identify close approached between covered missions and TLE from USSTRATCOM.…”

Section: Introductionmentioning

confidence: 99%

A high order method for orbital conjunctions analysis: Sensitivity to initial uncertainties

Morselli

Armellín

Lizia

et al. 2014

Advances in Space Research

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A high order method to quickly assess the effect that uncertainties produce on orbital conjunctions through a numerical high-fidelity propagator is presented. In particular, the dependency of time and distance of closest approach to initial uncertainties on position and velocity of both objects involved in a conjunction is studied. The approach relies on a numerical integration based on differential algebraic techniques and a high-order algorithm that expands the time and distance of closest approach in Taylor series with respect to relevant uncertainties. The modeled perturbations are atmospheric drag, using NRLMSISE-00 air density model, solar radiation pressure with shadow, third body perturbation using JPL's DE405 ephemeris, and EGM2008 gravity model. The polynomial approximation of the final position is used as an input to compute analytically the expansion of time and distance of closest approach. As a result, the analysis of a close encounter can be performed through fast, multiple evaluations of Taylor polynomials. Test cases with objects ranging from LEO to GEO regimes are considered to assess the performances and the accuracy of the proposed method.

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ESA’s process for the identification and assessment of high-risk conjunction events

Cited by 32 publications

References 7 publications

Considering the collision probability of Active Debris Removal missions

Considering the collision probability of Active Debris Removal missions

Conjunction Evolutions: The Process of Adapting and Evolving Operational Collision Warning Software from Server to Service Oriented Architecture

A high order method for orbital conjunctions analysis: Sensitivity to initial uncertainties

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