The Space Environment Sensor Suite (SESS) is the set of instruments of the National Polar-orbiting Operational Environmental Satellite System (NPOESS) that takes measurements to produce space-environment data products. The SESS includes a complement of instruments that provide in situ data on particles, fields, aurora, and the ionosphere. The SESS team consists of the NPOESS Integrated Program Office (IPO), Northrop Grumman Space Technology (NGST) - the prime contractor for NPOESS, Ball Aerospace & Technologies Corp. (BATC) - lead systems integrator for SESS, key instrument/algorithm suppliers, and the science community advisors who represent the future users of SESS data products. This team has developed a baseline design that addresses the NPOESS requirements for the SESS-specific in situ Environmental Data Records (EDRs). The SESS consists of a Thermal Plasma Sensor (TPS), a Low Energy Particle Sensor (LEPS), a Medium Energy Particle Sensor (MEPS), and a High Energy Particle Sensor (HEPS) that are distributed on the multi-orbit NPOESS system architecture to satisfy the user community's performance and coverage needs. This paper will present details on the SESS sensors and algorithms, the suite architecture, and their expected performance.