R Walker

Analysis of the effectiveness of space debris mitigation measures using the delta model

Abstract Firstly, the paper outlines the different space debris mitigation measures proposed or in use by the national space agencies in order to reduce and stabilise the predicted long-term growth of the space object population. The rationale for analysing the effectiveness of these different mitigation techniques with space debris models is introduced. Then, the features of Debris Environment Long Term Analysis (DELTA) model are described. Special attention is given to the DELTA model approach for the detailed simulation of realistic mitigation measure scenarios. The model predictions of long-term debris environment evolution for these scenarios are then analysed and discussed in terms of their relative efficiency in reducing the debris population and the consequences for the collision risks in key operational orbits.

THE SIMONE MISSION: LOW-COST EXPLORATION OF THE DIVERSE NEO POPULATION VIA RENDEZVOUS WITH MICROSATELLITES

The paper summarises a novel mission concept called SIMONE (Smallsat Intercept Missions to Objects Near Earth), whereby a fleet of microsatellites may be deployed to individually rendezvous with a number of Near Earth Objects (NEOs), at very low cost. The mission enables, for the first time, the diverse properties of a range of spectral and physical type NEOs to be determined. Such data are invaluable in the NEO scientific, impact damage prediction, and impact countermeasure planning contexts. The five identical 120kg spacecraft are designed for low-cost piggyback launch on the Ariane-5 into GTO, from where each uses a high specific impulse gridded-ion engine to escape Earth gravity and ultimately to rendezvous with a different NEO target. The primary challenge with such a mission is the ability to accommodate the necessary electric propulsion, power, payload and other onboard systems within the severe constraints of a microsatellite. The paper describes the way in which the latest technological advancements and innovations have been selected and applied to the mission design. The SIMONE design is feasible and clearly demonstrates that the mission objective of sampling a wide cross-section of the NEO population for both science and impact mitigation purposes is now realisable at relatively low cost.

Sensitivity of long-term orbital debris environment evolution to the deployment of nano-satellite swarms

Abstract Nano-satellites, classified as having a mass in the kilogram range, appear to be emerging as a growing industry in recent years. They offer affordable access to space on only a modest budget, or, due to their small size, they can be easily deployed in large numbers or ‘swarms’ in a distributed network for many different civil and military applications. However, if their popularity grows significantly, then the sheer number of nano-satellites added to the most populated regions of low Earth orbit would increase the collision risk and add to the space debris problem in the long-term. The current proposals for nano-satellite missions are reviewed in this paper. An overall outlook for the nano-satellite industry and for a nano-satellite launch traffic model is given. Then, a sensitivity study is conducted to analyse the long-term impact of nano-satellite swarms on the orbital debris environment for different generic mission designs. These designs vary in terms of the number of satellites and the satellite mass. It has been found that the deployment of a single nano-satellite swarm consisting of a thousand or more members into the most crowded region of low Earth orbit would have a modest, but observable impact on the future collision rate and debris population growth.

THE SIMONE MISSION: CLOSE RECONNAISSANCE OF THE DIVERSE NEO POPULATION AS A PRECURSOR TO IMPACT MITIGATION

The paper summarises a novel mission concept called SIMONE (Smallsat Intercept Missions to Objects Near Earth), whereby a fleet of microsatellites may be deployed to individually rendezvous with a number of Near Earth Objects (NEOs), at very low cost. The mission enables, for the first time, the diverse properties of a range of spectral and physical types of NEOs to be determined. Physical and compositional properties of NEOs are so varied between types that no single impact mitigation method will be applicable to all Earth-threatening objects. Instead, mitigation methods must be tailored to each type based on detailed data which can only be gathered by space missions conducting close reconnaissance of representative bodies of each type. The cost of mounting missions to rendezvous and survey multiple objects in the population would be very high using conventional spacecraft technology. However, in the paper we show how the latest technological advancements and innovations in propulsion and power systems, and instrument miniaturisation, enable microsatellites to perform this essential task at a fraction of the normal cost.