Wide-Field Infrared Explorer spacecraft system design

Following a formal and competitive process, the Wide-Field Infrared Explorer (WIRE) instrument was selected in 1994 to become a participant in NASA/Goddard Space Flight Center´s Small Explorer Program (SMEX). The WIRE instrument will be used to conduct a deep infrared, extra galactic science survey 500 times more sensitive than the Infrared Astronomy Satellite (IRAS) Faint Source Catalog. The WIRE instrument includes a cryogenically cooled (<7.5 K), 128×128 pixel, long wave, infrared detector embedded within an optical assembly which is cooled by a two-stage, solid-hydrogen cryostat. The WIRE spacecraft is being configured to be placed into a 470×540 km sun-synchronous orbit using an Orbital Sciences Corporation Pegasus XL launch vehicle. Total spacecraft mass will be less than 275 kg. Orbit average power consumed will be less than 175 W. The WIRE instrument will be delivered to NASA/Goddard Space Flight Center in early 1998 to undergo integration and test with the WIRE spacecraft bus and subsequently will be launched in the fall of 1998. The SMEX program uses a strict design-to-cost approach to manage and to contain overall mission cost. This paper will present the major instrument, operational and cost requirements driving the spacecraft systems design for the mechanical, structural, thermal, attitude control, command and data handling, power and electrical systems. It will document major system trade studies results and the subsequent spacecraft design to meet mission requirements