proposed question/mission: If the equatorial ridge on Iapetus is theorised to be caused by the materials left by a collapsed ring, then Saturn’s rings are made of the same substance as the ridge. 
research many of the instruments that were similar and have been used in the past. (pick one: UV Spectrometer, LRO lamp, imaging cameras, particle analysers). 
Come up with design changes to the chosen instrument that will be beneficial to this mission in particular. 

Describe what is new and different about this instrument compared to instruments that were used for similar purposes in the past (or for planned future missions). If it is based on a previous instrument, what modifications have been made to suit the purposes of your mission? 
How much is this instrument going to weigh and how much room does this instrument take? 
provide a report on this new instrument and explain how it will work in the expected environment of the location for this mission (Iapetus). 
explain the new challenges that will arise for exploring this location for the proposed science questions of the mission and whether any innovations can be made.