This project is an attempt to determine if the low-cost small satellite design methodology pioneered over the last few years by organizations such as the University of Surrey's Centre for Satellite Engineering Research can be applied to a low-cost, rapid-response space probe. Such a probe should be ideally be able to be sent to investigate newly-discovered near-Earth objects such as closely-approaching asteroids. This is in contrast to traditional space probe design where spacecraft are custom-built for a particular mission that is planned years in advance.

This report takes the form of a feasibility and initial design study for a rapid-response space probe. It explores the justification for such a mission and introduces the design approach adopted in this study. It then covers the nature of the mission's potential targets and identifies the science objectives appropriate to them. The major mission options are specified and selected and from this the requirements for the space probe in terms of propulsion, attitude control, power, communications and data handling are estimated. These requirements are used to produce a conceptual design for the probe which is then subjected to basic structural and thermal modelling. A mass budget and cost estimate for the final probe configuration are then produced. Finally, consideration is given to the implications for mission operations of a rapid-response space probe and areas for follow-on work are suggested.

It is concluded that it is feasible to carry out such a mission via a probe with a launch mass of 116 kg, plus 670 kg for the requisite solid propellant boost motor to inject it into the trajectory required to carry out a rapid intercept of the target asteroid. This mass allows a margin of 24 kg within the specified trajectory performance. The probe would be launched following identification of a suitable target, via either a small satellite launcher or one of a number of proposed reusable launch vehicles. It would then carry out a high-speed flyby (at up to 20 km/s) of the target at a range of up to 7.5 million km from Earth after a flight time of within 3 weeks. The probe would approach the target to within several hundred km, carrying out a carefully-controlled slew to allow its high-resolution imaging system to capture a stream of multispectral images of the target. These would be compressed and stored in solid-state memory for subsequent downlink to Earth via the probe's X-band communications system. The overall cost of such a mission is estimated as being in the range $7.5 - 41 million, with a probable cost of $18.5 - 28.5 million depending on the available launch system.

This project was carried out as the Level M Dissertation for the degree of Master of Science in Satellite Communications Engineering, undertaken as a part-time course 1995-1997. It should be noted that although this project was carried out under the supervision of a staff member of the Centre for Satellite Engineering Reseach and Surrey Satellite Technologies, my being in full-time employment precluded my working for any time within CSER or SSTL and so this project was carried out independently of their small satellite programme (except for quoted references). It was also carried out completely independent of any involvement of my employer (the Ministry of Defence).

One of the hazards of doing an MSc on a part-time basis is that the project work is inevitably stretched out for longer than usual (in this case, from October 1996 to August 1997). I would thus like to particularly thank a number of people who have helped me and/or put up with me during my project work for longer than might normally be expected! I would of course like to particularly thank my supervisor, Dr Craig Underwood, for much enthusiasm and advice - even if I did chicken out as regards his preference for the mission name (alas, discretion is the better part of valour). Equally I would like to thank my partner Bridget for her love, understanding and interest, especially during the busy final stages of the project; I hope I am able to be as good to her as she finishes her own thesis. I would also like to thank my employers for releasing me for this course and my colleagues for helping smooth out the effects of my periodic absences. Finally, my family and friends also provided help and encouragement.

This project is dedicated to the memory of two people. Firstly, my father Denis, who sadly is not here to see me finish this course. Additionally it is dedicated to Dr Eugene Shoemaker, who died shortly before its completion. Gene Shoemaker was the father of asteroid geology and was deeply involved in studies for potential missions to such objects. By good fortune I had the pleasure of meeting him a few months ago; a fascinating and enthusiastic exponent of his field, he is sorely missed by many.

Simon Bradshaw

August 1997