Improved motion-mode estimation

Hybrid trackers incorporating a non-Markov modal model have been proposed. However, these algorithms use a restricted measurement set to identify the modal state. It is shown here that a renewal process model, along with broader measurement fusion, enhances modal classification in such estimators.     

Tracking a maneuvering target using sensors of variable quality

In an environment subject to sudden change, the accuracy of tracking and prediction is strongly influenced both by the sensor architecture and by the quality of the sensors. An image-enhanced algorithm is presented for both path following and covariance estimation in applications where the sensors are subject to sudden and unpredictable variation in quality. For an illustrative trajectory, the performance of the algorithm is contrasted with an extended Kalman filter (EKF) and an image-enhanced algorithm based upon the nominal sensors     

Calibration of the Mars Science Laboratory Alpha Particle X-ray Spectrometer

The alpha-particle X-ray spectrometer (APXS) for the Mars Science Laboratory (MSL) mission was calibrated for routine analysis of: Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Zn, Br, Rb, Sr, and Y. The following elements were also calibrated, but may be too low to be measured (10s–100s ppm) for their usual abundance on Mars: V, Cu, Ga, As, Se and W. An extensive suite of geological reference materials, supplemented by pure chemical elements and compounds was used. Special attention was paid to include phyllosilicates, sulfates and a broad selection of basalts as these are predicted minerals and rocks at the Gale Crater landing site. The calibration approach is from first principles, using fundamental physics parameters and an assumed homogeneous sample matrix to calculate expected elemental signals for a given instrument setup and sample composition. Resulting concentrations for most elements accord with expected values. Deviations in elements of lower atomic number (Na, Mg, Al) indicate significant influences of mineral phases, especially in basalts, ultramafic rocks and trachytes. The systematics of these deviations help us to derive empirical, iterative corrections for different rock groups, based on a preliminary APXS analysis which assumes a homogeneous sample. These corrections have the potential to significantly improve the accuracy of APXS analyses, especially when other MSL instrument results, such as the X-ray diffraction data from CheMin, are included in the overall analysis process.     

The Swift Ultra-Violet/Optical Telescope

The Ultra-Violet/Optical Telescope (UVOT) is one of three instruments flying aboard the Swift Gamma-ray Observatory. It is designed to capture the early (∼1 min) UV and optical photons from the afterglow of gamma-ray bursts in the 170–600 nm band as well as long term observations of these afterglows. This is accomplished through the use of UV and optical broadband filters and grisms. The UVOT has a modified Ritchey–Chrétien design with micro-channel plate intensified charged-coupled device detectors that record the arrival time of individual photons and provide sub-arcsecond positioning of sources. We discuss some of the science to be pursued by the UVOT and the overall design of the instrument.     

Optically tuneable photonic crystal waveguides

Incorporation of DNA into nanoscale wells in a silicon substrate has been demonstrated to show fabrication feasibility for optically tunable photonic crystal waveguides. A change in propagation characteristics due to DNA incorporation has been observed for a silicon-on-insulator photonic crystal waveguide.     

Numerical modeling of spacecraft electric propulsion thrusters

There is a clear current trend towards the replacement of small chemical thrusters used for spacecraft control by electric propulsion thrusters. These thrusters use a variety of mechanisms to convert electrical power into thrust and, in general, provide superior specific impulse in comparison to chemical systems. Electric propulsion has been under development for the last 40 yr, and almost all thrusters are designed based on experience and experimentation. The present article considers the progress made in numerical simulation of electric propulsion thrusters. Due to the wide range of such devices, attention is restricted to electric propulsion thruster types that are presently in use by orbiting spacecraft. The physical regimes created in these thrusters indicate that a variety of numerical methods is required for accurate numerical simulation ranging from continuum formulations to kinetic approaches. Successes of numerical simulation models are demonstrated through specific examples. It is concluded that numerical simulations can be expected to play a more prominent role in the design and evolution of future electric propulsion thrusters.     

Measurement of electric fields in the ionosphere and magnetosphere

Space Science Reviews -     

Psychology and culture during long-duration space missions

The objective of this paper is twofold: (a) to review the current knowledge of cultural, psychological, psychiatric, cognitive, interpersonal, and organizational issues that are relevant to the behavior and performance of astronaut crews and ground support personnel and (b) to make recommendations for future human space missions, including both transit and planetary surface operations involving the Moon or Mars. The focus will be on long-duration missions lasting at least six weeks, when important psychological and interpersonal factors begin to take their toll on crewmembers. This information is designed to provide guidelines for astronaut selection and training, in-flight monitoring and support, and post-flight recovery and re-adaptation.