A COMBINED SPACECRAFT AND LAUNCH VEHICLE SYSTEMS APPROACH TO MISSION DESIGN FOR THE IRIS MISSION

The Interface Region Imaging Spectrograph (IRIS) mission was launched in June 2013 on a Pegasus XL launch vehicle. To perform its solar observations, the IRIS spacecraft required periods of continuous eclipse-free viewing of the Sun. A typical spacecraft mission will have a well-defined orbit solution early in the planning phases. IRIS, however, was driven by science requirements, and did not require a specific mission orbit. Therefore, the selection of the mission orbit was made using a unique approach. The design team performed an integrated systems analysis approach to achieve a final mission orbit design that balanced the launch vehicle trajectory and performance with optimizing the IRIS science goals, to meet and exceed the requirements. This paper details the results of the integrated spacecraft and launch vehicle mission design trade studies that led to the final orbit targets and the Pegasus launch vehicle guidance scheme utilized for the IRIS mission. The actual achieved results are also presented.