Space Shuttle UHF communications performance evaluation

Computational investigations and experimental measurements were performed to evaluate the Space Shuttle UHF communication system performance for payload bay antenna at the proposed new location. To insure adequate communication coverage at relocated new location, the link margin for the Extravehicular Activity (EVA) astronauts and between Space Shuttle Orbiter and International Space Station (SSO-ISS) during rendezvous were analyzed. The multipath effects from the vehicle structures surrounding the antenna were investigated. The Radio Frequency (RF) electromagnetic radiation to the Orbiter Docking System (ODS) pyrotechnics was also analyzed to ensure the EMC/EMI compliances.     

Covariance Matrix for ?-?-? Filtering

Closed-form expressions are derived for the output noise response of an ?-?-? filter in steady-state operation with constant measurement noise statistics. To the author's knowledge such expressions have been unavailable until now. These formulas are useful for target tracking applications.     

Time-dependent thermal X-ray afterglows from GRBS

Time-dependent thermal X-ray spectra are calculated from physically plausible conditions around GRB. It is shown that account for time-dependent ionization processes strongly affects the observed spectra of hot rarefied plasma. These calculations may provide an alternative explanation to the observed X-ray lines of early GRBs afterglows (such as GRB 011211). Our technique will allow one to obtain independent constraints on the GRB collimation angle and on the clumpiness of circumstellar matter.     

The Fine Structure of the AKR Electromagnetic Field as Measured by the Interball-2 Satellite

The fine structure of the Auroral Kilometric Radiation (AKR) is studied using multicomponent measurements of the electric component of the electromagnetic field in the frequency band 4 kHz–1 MHz (the POLRAD experiment onboard the INTERBALL-2 satellite). Special attention is paid to the measurements near the source of the AKR: under conditions when the lower boundary of the emission range descended sufficiently low, down to the local gyrofrequency of electrons. From the analysis of the electric field structure the conclusion is drawn that the bulk of the AKR power is carried by the signal component fast variable in time and frequency (flickering component). The power of a constant component (continuum) is lower by at least an order of magnitude. During strong bursts of the AKR, the relative contribution of the flickering component increases. The spatial structure of the zone of generation has at least three characteristic scales along and across the magnetic field.     

Space experiment on behaviors of treefrog.

Japanese treefrogs (Hyla japonica) are planned to be sent to the space station MIR. Experimental system was developed to observe their behaviors under microgravity.     

Aperture error mitigation via local-state estimation for frequency-based emitter location

This paper considers the problem of locating a stationary coherent emitter via a single moving platform making frequency measurements in the presence of aperture state uncertainty. It is shown that the estimated emitter location is most sensitive to the receiving aperture velocity uncertainty. The required aperture velocity accuracy is determined through a noninfinitesimal perturbation analysis. A solution to location accuracy enhancement with a minimal hardware addition is attempted. It is shown that this can be achieved by mounting a high-resolution tri-axis microelectromechanical systems (MEMS) accelerometer at the aperture to measure its velocity, which can deviate significantly from that estimated by the on-board navigation system. The Doppler shifts of the GPS signal carrier frequency, whenever it can be acquired through the aperture, are also considered as a way to aid the aperture velocity measurement. A decentralized, federated processing method for the aperture velocity estimate referenced at the aperture, integrating all measurement data, is presented. An upper bound for the error of aperture velocity estimate is derived. The potential for significant accuracy enhancement for emitter location is demonstrated.     

The double-pulsar binary J0737–3039

A recent multibeam pulsar survey of the outer Galactic plane at Parkes has discovered the first-known double-pulsar binary, a very compact double neutron star system in which both stars are observable as radio pulsars. In this review, we briefly describe the discovery and the studies which have been enabled by the unique properties of the system. These range from the most precise confirmation yet of the theory of general relativity, with the possibility of even more new tests and the measurement of second-order post-Newtonian effects, to studies of the magnetospheres and emission properties of the two pulsars. The discovery also results in a significant increase in the expected rate of occurrence of the mergers of double neutron star systems, and hence the rate of detection of such events by the new ground-based gravitational wave detectors.     

Power anomaly effects and costs in low-voltage mobile power systems

Electric power anomalies or disturbances can disrupt the normal operation of equipment, accelerate aging, or even cause outright failures thus resulting in increased costs of maintenance and reduced system reliability. Past research on the effects caused by power anomalies has been mostly focused on industrial, commercial, or residential systems, or on power distribution equipment. A literature survey reveals that there is no comprehensive review related to low-voltage (LV) power systems and utilization equipment applicable to military combat vehicles, such as aircraft and ships. This paper summarizes the results of a new literature survey that focused on the causes, effects, and mitigation methods for power anomalies typical of LV mobile power systems. Electric power anomaly cost data collected from the literature are also presented, from which the costs of anomalies to the national defense are estimated using some simple rationales.     

Advanced lithium ion battery charger

A lithium ion battery charger has been developed for four and eight cell batteries or multiples thereof. This charger has the advantage over those using commercial lithium ion charging chips in that the individual cells are allowed to be taper charged at their upper charging voltage rather than be cutoff when all cells of the string have reached the upper charging voltage limit. Since 30-60% of the capacity of lithium ion cells may be restored during the taper charge, this charger has a distinct benefit of fully charging lithium ion batteries by restoring all of the available capacity to all of its cells