The Radiation Belt Storm Probes (RBSP) and Space Weather

Following the launch and commissioning of NASA’s Radiation Belt Storm Probes (RBSP) in 2012, space weather data will be generated and broadcast from the spacecraft in near real-time. The RBSP mission targets one part of the space weather chain: the very high energy electrons and ions magnetically trapped within Earth’s radiation belts. The understanding gained by RBSP will enable us to better predict the response of the radiation belts to solar storms in the future, and thereby protect space assets in the near-Earth environment. This chapter details the presently planned RBSP capabilities for generating and broadcasting near real-time space weather data, discusses the data products, the ground stations collecting the data, and the users/models that will incorporate the data into test-beds for radiation belt nowcasting and forecasting.     

How the science and engineering of spaceflight contribute to understanding the plasticity of spinal cord injury.

Space programs support experimental investigations related to the unique environment of space and to the technological developments from many disciplines of both science and engineering that contribute to space studies. Furthermore, interactions between scientists, engineers and administrators, that are necessary for the success of any science mission in space, promote interdiscipline communication, understanding and interests which extend well beyond a specific mission. NASA-catalyzed collaborations have benefited the spinal cord rehabilitation program at UCLA in fundamental science and in the application of expertise and technologies originally developed for the space program. Examples of these benefits include: (1) better understanding of the role of load in maintaining healthy muscle and motor function, resulting in a spinal cord injury (SCI) rehabilitation program based on muscle/limb loading; (2) investigation of a potentially novel growth factor affected by spaceflight which may help regulate muscle mass; (3) development of implantable sensors, electronics and software to monitor and analyze long-term muscle activity in unrestrained subjects; (4) development of hardware to assist therapies applied to SCI patients; and (5) development of computer models to simulate stepping which will be used to investigate the effects of neurological deficits (muscle weakness or inappropriate activation) and to evaluate therapies to correct these deficiencies.     

Radioprotection by metals: selenium.

The need exists for compounds that will protect individuals from high-dose acute radiation exposure in space and the agents that might be less protective but less toxic and longer acting. Metals and metal derivatives provide a small degree of radioprotection (dose reduction factor < or = 1.2 for animal survival after whole-body irradiation). Emphasis is placed here on the radioprotective potential of selenium (Se). Both the inorganic salt, sodium selenite, and the organic Se compound, selenomethionine, enhance the survival of irradiated mice (60Co, 0.2 Gy/min) when injected IP either before (-24 hr and -1 hr) or shortly after (+15 min) radiation exposure. When administered at equitoxic doses (one-fourth LD10; selenomethionine = 4.0 mg/kg Se, sodium selenite = 0.8 mg/kg Se), both drugs enhanced the 30-day survival of mice irradiated at 9 Gy. Survival after 10-Gy exposure was significantly increased only after selenomethionine treatment. An advantage of selenomethionine is lower lethal and behavioral toxicity (locomotor activity depression) compared to sodium selenite, when they are administered at equivalent doses of Se. Sodium selenite administered in combination with WR-2721, S-2-(3-aminopropylamino)ethylphosphorothioic acid, enhances the radioprotective effect and reduces the lethal toxicity, but not the behavioral toxicity, of WR-2721. Other studies on radioprotection and protection against chemical carcinogens by different forms of Se are reviewed. As additional animal data and results from human chemoprevention trials become available, consideration also can be given to prolonged administration of Se compounds for protection against long-term radiation effects in space.     

Protocol for the treatment of radiation injuries.

Despite adequate precautionary measures and high-quality safeguard devices, many accidental radiation exposures continue to occur and may pose greater risks in the future, including radiation exposure in the space environment. The medical management of radiation casualties is of major concern to health care providers. Such medical management was addressed at The First Consensus Development Conference on the Treatment of Radiation Injuries, Washington, DC, 1989. The conference addressed the most appropriate treatment for the hematopoietic and infectious complications that accompany radiation injuries and for combined radiation and traumatic/burn injuries. Based on the evidence presented at the conference, a consensus statement was formulated by expert physicians and scientists. The recommended therapies, including a suggested algorithm incorporating these recommendations for the treatment of radiation injuries, will be discussed.     

Stability of motion of a space vehicle under constantly acting disturbances

The attitude stability of an Earth-orbiting satellite experiencing aerodynamic torque is studied. This is accomplished by applying the theory of total stability (or, stability under constantly acting disturbances) to the equations of motion. The satellite is gravity-gradient stabilized and a damping torque is incorporated. The aerodynamic torque results from the presence of two flat panels attached to the cylindrical body of the vehicle. This perturbing torque is treated as an additive disturbance in Euler's equations of motion. A Lyapunov function is constructed and then used in an appropriate theorem on stability under constantly acting disturbances. Explicit expressions are thereby found for bounds on a hypothetical initial condition (a rotation from the Earth-pointing equilibrium) and on the aerodynamic torque, so that if these disturbances are less than their respective bounds then the resulting attitude motion of the satellite will not exceed a pre-assigned value. These bounds depend on that pre-assigned value, and on the physical parameters of the satellite. The design implications of these bounds are then discussed.     

Cyclicality or volatility? The satellite insurance market

The history of the satellite insurance market indicates that this market experiences crises and booms in profitability and prices that repeat in a manner suggestive of cycles. The purpose of this article is to rigorously investigate cyclicality of these and other features of the satellite insurance market and assess their volatility formally. Using data from 1968 to 2008, volatility and cyclicality are analyzed for satellite insurance market capacity, rates, and underwriting results, among other measures. The coefficient of variation for the various satellite insurance market metrics is used to assess volatility. Standard underwriting analysis is used to determine whether a cycle exists for various insurance metrics. The results indicate that some aspects of the satellite insurance market are volatile (e.g. claims) or cyclical (e.g. rates), while capacity is both volatile and cyclical.     

Kalman filtering for matrix estimation

A general discrete-time Kalman filter (KF) for state matrix estimation using matrix measurements is presented. The new algorithm evaluates the state matrix estimate and the estimation error covariance matrix in terms of the original system matrices. The proposed algorithm naturally fits systems which are most conveniently described by matrix process and measurement equations. Its formulation uses a compact notation for aiding both intuition and mathematical manipulation. It is a straightforward extension of the classical KF, and includes as special cases other matrix filters that were developed in the past. Beyond the analytical value of the matrix filter, it is shown through various examples arising in engineering problems that this filter can be computationally more efficient than its vectorized version.     

Performance Evaluation of Postdetection Integrators with Partially Correlated Noise

A simple procedure for calculating receiver operating characteristics (ROC) for postdetection integration of arbitrary partially correlated noise samples is presented. The approach is based on the application of the ?effective number of independent integrated noise samples? to the classical theory of Marcum and Swerling and has been justified by Monte-Carlo simulation.     

Performance analysis of bearing-only target location algorithms

The performance of two well-known bearing-only location techniques, the maximum likelihood (ML) and the Stansfield estimators, is examined. Analytical expressions are obtained for the bias and the covariance matrix of the estimation error, which permit performance comparison for any case of interest. It is shown that the Stansfield algorithm provides biased estimates even for large numbers of measurements, in contrast with the ML method. The RMS error of the Stansfield technique is not necessarily larger than the RMS of the ML technique. However, it is shown that the ML technique is superior to the Stansfield method when the number of measurements is large enough. Simulation results verify the predicted theoretical performance