Early development of the first earth venture mission: How CYGNSS is using Engineering Models to validate the design

In response to the recommendations made in the National Research Council´s Earth Science and Applications 2007 Decadal Survey, NASA has initiated the Earth Venture line of mission opportunities. The first orbital mission chosen for this competitively selected, cost and schedule constrained, Principal Investigator-led opportunity is the CYclone Global Navigation Satellite System (CYGNSS). The goal of CYGNSS is to understand the coupling between ocean surface properties, moist atmospheric thermodynamics, radiation, and convective dynamics in the inner core of a tropical cyclone. The CYGNSS mission is comprised of eight Low Earth Observing (LEO) microsatellites that use GPS bi-static scatterometry to measure ocean surface winds. As specified in the selecting Announcement of Opportunity, the Principal Investigator (PI) for CYGNSS is held responsible for successfully achieving the science objectives of the selected mission and the management approach that he chooses to obtain those results has a significant amount of freedom as long as it meets the intent of key NASA guidance. The development approach chosen for the implementation of CYGNSS has several facets. One foundational tenant of the Class D approach chosen by CYGNSS was to maximize the use of off-the-shelf components and then offset this higher mission risk posture by early and thorough testing of multiple Engineering Models. This not only tested hardware and software but it allowed for exercising of Assembly, Integration, and Test (AI&T) processes and procedures before ever building the flight units. The CYGNSS team is currently in Phase C of the Project Life Cycle. Not only is the design continuing to mature but AI&T of three microsatellite engineering models, each with its own objectives, are in progress. Testing of the Engineering Model (EM), the Structural Thermal Model (STM), and the Radio Frequency Model (RFM) has commenced and a discussion on the purpose and progress made to date of each of th- se engineering models as well as some associated lessons learned is presented in this paper.