Students of the MSc course in Astronautics and Space Engineering 2006/07 at Cranfeld University took the Precursor Rendezvous for Impact Mitigation of Asteroids (PRIMA) mission as one of their group projects. This report summarises their fndings. Asteroid impacts have shaped Earth's development in the past and they will continue to do so in the future. Large asteroid impacts are acts of nature beyond our ability to mitigate, but the much more frequent impacts with continental rather than global scale can now be prevented in many cases. Effective impact prevention depends on good knowledge of the asteroid threat: the PRIMA mission's goal is to obtain enough information about an asteroid's orbit and composition to enable impact prevention. This PRIMA study's objective is a feasible mission design. The asteroid Apophis was chosen as the prime target because it is representative of the most likely impact risk and it is also the highest current asteroid threat to Earth. To develop the baseline design the team initially identifed a range of mission concepts and then chose the best of these using a trade-off based on the concepts' various attributes. The next phase was to develop outline designs for each sub-system, focussing on issues which could affect mission feasibility. The resulting baseline design consists of a 600 kg spacecraft with electric propulsion and a lander containing a tracking beacon which is placed on Apophis. Asteroid composition is measured by radar and seismometry. All results so far indicate that this concept is feasible, although further work is required especially in the areas of low- thrust trajectories for asteroid rendezvous, and technologies for the tracking transponder, measuring asteroid composition, and attaching equipment to an asteroid where gravity is weak and surface composition is uncertain.