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The Stratospheric Observatory for Infrared Astronomy (SOFIA), a joint project between NASA and the German Aerospace Center DLR, provides access to observations of the infrared and sub-millimeter universe. As its development timeline is unique compared to all other NASA astrophysics missions, a milestone called the Full Operation Capability (FOC) was defined to identify the start of science operations. SOFIA reached this in February 2014. With a wide range of imagers, spectrometers and a new polarimeter, SOFIA provides unique scientific results that cannot be obtained with a ground-based facility and any spacecraft expected in the next decade. The airborne platform has continued to mature its mission systems as part of a planned spiral development approach, particularly with upgradable instrumentation that opens up new science directions for the Observatory. A third generation instrument is planned for commissioning in 2019. This paper summarizes the current state of the Observatory with emphasis on the science and instrumentation updates since FOC.

The primary mission of International Space Station (ISS) is to provide a shirt-sleeve working environment within an orbiting laboratory to support a wide variety of research conducted in the micro-gravity (μ-gravity) environment of space. The laboratory being developed by the Space Station Biological Research Project (SSBRP) at the Ames Research Center (ARC) will support NASA’s Gravitational Biology and Ecology (GB&E) Research Program on the influence and affects of gravity on living systems. It will support research from the building blocks of biology (cells and tissues) through complete, fully grown systems (plants, rodents, aquatics and insects) and through all phases of growth as well as multiple generations. The results will provide an in-depth understanding of the role of gravity in living systems. It should provide the information necessary to support long-term manned missions for exploration of the solar system. In addition, it is expected to provide valuable insight into how Earth-bound biological systems work.

The Space Infrared Telescope Facility (SIRTF) is a cryogenically cooled, space based, one meter class telescope for infrared astronomy. A recent mission option study has moved SIRTF from a previous low earth orbit (900 km) shuttle launched design to a high earth orbit (100,000 km) Titan IV/Centaur launched design. The mission option study requirements and trades relating to the structural configuration and the chosen SIRTF design are described. Also discussed is a dynamic stress analysis of the new SIRTF baseline structural design which has been performed using finite element modeling and simulated launch interface loads.

The primary mirror assembly (PMA) requirements and concepts for the Space Infrared Telescope Facility (SIRTF) program are discussed. The PMA studies at NASA/ARC resulted in the design of two engineering test articles, the development of a mirror mount cryogenic static load testing system, and the procurement and partial testing of a full scale spherical mirror mounting system. Preliminary analysis and testing of the single arch mirror with conical mount design and the structured mirror with the spherical mount design indicate that the designs will meet all figure and environmental requirements of the SIRTF program.

The NASA Ames Research Center has developed a baseline design for a One Meter Cryogenic Optical Test Facility (OMF) incorporating a liquid helium Dewar for cryogenic optical testing of one-meter-class mirrors, principally the Space Infrared Telescope Facility (SIRTF) primary mirror. The primary requirements for the test facility are as follows: 1) The facility must be capable of interferometrically testing any mirror, positioned face-up or face-down, with a diameter less than 1.5 meters and a radius of curvature from 1.5 to 5.5 meters. 2) The facility must achieve and maintain, for 24 hours, a mirror temperature of 4 K with a maximum radiative heat load of less than 500 mW to the mirror, using stored liquid helium and liquid nitrogen. 3) The facility must include a vibration-isolated metrology structure between the test mirror and an external interferometer. 4) The facility must be operated by two persons and a test, starting from the mounting of a mirror to the removal of a mirror, must be conducted within one week.

The Space Infrared Telescope Facility (SIRTF) mission based on a cryogenically cooled telescope is described. The SIRTF makes it possible to perform background limited measurements with three focal plane instruments in the wavelength range 2-700 microns over the entire celestial sphere for at least five years. A telescope performance limited by the natural astrophysical background between 2 to 300 microns is achieved by using a superfluid helium cryogenic system for maintaining the forebaffle temperature below 8 K. The attitude control system based on Extreme Ultra-Violet Explorer reaction wheels meets the large and small angle slew requirements and provides 0.15 arc sec pointing stability. The present HEO baseline configuration has a mass of 4370 kg. The future Titan IV/Centaur launch capability to 100,000 km for a SIRTF-sized payload is at least 5770 kg.

Among the design objectives for large space structures are the maintenance of tight dimensional tolerance and the reduction of settling time after disturbance input. Two options are under consideration for the design of flexible structures to meet these objectives, including an active control option and a passive control option. In connection with both options, it is necessary to include material and structural damping in the design. A description is presented of the results of an experimental investigation of the damping of metallic and fibrous composite materials, taking into account also the analytical modeling and experimental verification of frictional damping schemes. To demonstrate how material and frictional damping can be combined, a simple structural optimization is performed, indicating the potential for significant savings in mass by the addition of frictional dampers.