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High precision pointing and vibration control of future spacecraft and satellites
The Middeck Active Control Experiment (MACE) is a United States Space Shuttle flight experiment manifest for launch on STS-67 in February, 1995. MACE (Figure la) was designed by the Space Engineering Research Center at the Massachusetts Institute of Technology, in collaboration with Payload Systems Incorporated, the NASA Langley Research Center, and Lockheed Missiles and Space Company. The goal is to explore approaches to achieving high precision pointing and vibration control of future spacecraft and satellites. In particular, MACE extends the bandwidth of conventional rigid body instrument pointing and attitude controllers to include the flexible modes of the satellite. Since the success of such flexible control is intimately dependent upon the accuracy of the spacecraft model used for control design, MACE is essentially a spacecraft modeling validation effort where success is determined by the control performance and predictability that is achieved in earth orbit. MACE builds upon the concept of the Middeck 0-Gravity Dynamics Experiment (MODE), which flew on STS-40, STS-48 and STS-62 as a dynamics test facility to characterize fluid, Space Station structure, and crew motion dynamics in zero- gravity. MACE augments the MODE facility with real-time, digital control capabilities.
X-ray space telescope payload being developed for NASA's sounding rocket program.
The Micro-X mission is a rocket-borne telescope with a new type of X-ray detector that will revolutionize X-ray astrophysics and the use of high resolution X-ray spectroscopy. Our detectors, called Transition-edge Sensor (TES) Microcalorimeters, measure the energy of a photon by sensing the small change in temperature when the photon is absorbed in the TES. With TESs, the combination of high energy resolution, high efficiency, precise timing, and potential for true imaging spectroscopy at X-ray energies is unparalleled by any other technology today. TESs are being developed for future NASA missions like IXO, and will open up new frontiers in our ability to study black holes and strong gravity, dark matter, dark energy, the evolution of structure formation in our universe and the cycles of matter and energy. Micro-X will be a multi-flight program. Future flights may study a varied set of astrophysical problems, among them the physics of the cores of clusters of galaxies, and the physics of accretion, jets, and outflows in neutron stars and black holes in bright X-ray binaries.
Suspension and gravity influences on the structural dynamics of a modular truss system
The increasingly demanding performance requirements on spacecraft require a detailed model of all dynamic components. If a spacecraft structure is to be an element of the plant in a robust closed loop control system, a high premium is placed on the accuracy of the structural model. The problem is that the accuracy of first generation numerical structural models, and even second generation models, cannot be guaranteed within any stated bounds. Accuracy is degraded as a result of poor modeling due to inexact elements and boundary conditions, mismodeling, and nonmodeling of features such as damping and weak nonlinearities. The approach of using ground experimental results to update a structural model is limited in that ground modal identification of complete spacecraft is not always possible, and when conducted, yields results corrupted by gravity and suspension effects. The objectives of the Middeck 0-Gravity Dynamics structural Experiment (MODE) were to study suspension and gravity influences on the structural dynamics of a modular truss system by comparing the measured response in ground and orbital tests and to quantify the suspension and gravity induced perturbations using analytical models of the suspension and nonlinear effects. The repeatability of measured modal properties from test to test and from test article to test article was also examined. The final MODE objective was to develop a component testing procedure that will yield the information necessary to update second generation structural models to obtain the accuracy desired for the design of robust and high performance closed loop controllers. MODE was funded by IN-STEP in 1988 and flew on board STS-48 in September 1991. The research, design and development were a combined effort of MIT SERC, Payload Systems Inc. and Mide Technology Corporation.
An X-ray Imaging Spectrometer aboard NASA's OSIRIS-REx Mission
OSIRIS-REx (Origins Spectral Interpretation Resource Identification Security Regolith Explorer) will be the third spacecraft launched as part of NASA’s New Frontiers program. As part of the New Frontiers mission to research the solar system, OSIRIS-REx will characterize and return to Earth a sample of the near-Earth carbonaceous chondrite asteroid 1999 RQ36. The Regolith X-ray Imaging Spectrometer (REXIS) is the tool for conducting the student collaboration experiment (SCE) on the OSIRIS-REx 1999 RQ36 sample return mission. REXIS provides a valuable scientific enhancement to the OSIRIS-REx mission by obtaining an X-ray (0.3-7.5 keV) global map of the elemental abundance of 1999 RQ36. This global X-ray map will provide complementary understanding of the globally representative returned sample, thus providing a greater understanding of the composition of 1999 RQ36.
CMG-Based Stability for EVAs near Low-Gravity Objects
Utilizing control moment gyroscopes (CMGs) for increased stability of the simplified aid for EVA rescue (SAFER) jet pack system during extravehicular activities (EVA)