Nigel Wells

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.

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.

Measurement requirements for a near-earth asteroid impact mitigation demonstration mission

A concept for an Impact Mitigation Preparation Mission, called Don Quijote, is to send two spacecrafts to a Near-Earth Asteroid (NEA): an Orbiter and an Impactor. The Impactor collides with the asteroid while the Orbiter measures the resulting change in the asteroids orbit, by means of a Radio Science Experiment (RSE) carried out before and after the impact. Three parallel Phase A studies on Don Quijote were carried out for the European Space Agency: the research presented here reflects the outcomes of the study by QinetiQ. We discuss the mission objectives with regard to the prioritisation of payload instruments, with emphasis on the interpretation of the impact. The Radio Science Experiment is described and it is examined how solar radiation pressure may increase the uncertainty in measuring the orbit of the target asteroid. It is determined that to measure the change in orbit accurately a thermal IR spectrometer is mandatory, to measure the Yarkovsky effect. The advantages of having a laser altimeter are discussed. The advantages of a dedicated wide-angle impact camera are discussed and the field-of-view is initially sized through a simple model of the impact.