An Application of Kalman Filtering and Time Averaging to Inertial Guidance Evaluation

A method is developed for estimating circular error probable values and circular error probable rate values of an inertial navigation system using the concepts of Kalman filtering and time averaging.     

Resonant sensor for high accuracy pressure measurement usingsilicon technology

A resonant-element transducer developed for aerospace applications using micromachined silicon technology is described. The sensor is a beam supported over a square diaphragm. The resonant frequency of the beam is proportional to the applied pressure on the diaphragm. Results presented show that the prototype's performance rivals that of current high-accuracy pressure transducers     

Results from the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Observatory

The Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory covers the high energy gamma ray energy range, approximately 30 MeV to 30 GeV, with a sensitivity considerably greater than earlier high energy gamma-ray satellites. Thus far, 4 pulsars have been detected and their properties measured, including in 3 cases the energy spectrum as a function of phase. The details of the galactic plane are being mapped and a spectra of the center region has been obtained in good agreement with that expected from cosmic ray interactions. The Magellanic clouds have been examined with the Large Magellanic Cloud having been detected at a level consistent with it having a cosmic ray density compatible with quasi-stable equilibrium. Sixteen Active Galactic Nuclei (AGN's) have been seen thus far with a high degree of certainty including 12 quasars and 4 BL Lac objects, but no Seyferts. Time variation has been detected in some of these AGN's.     

Adaptive imaging for forward-looking ground penetrating radar

Most of the current forward-looking ground-penetrating radar (FLGPR) systems use conventional delay-and-sum (DAS) based methods to form radar images for detection of the target (such as a landmine). However, DAS is a data-independent approach which is known to suffer from low resolution and poor interference and clutter rejection capability. We present a data-adaptive imaging approach for FLGPR image formation based on APES (amplitude and phase estimation) and rank-deficient RCB (robust Capon beamforming). Due to the data-adaptive nature of both APES and RCB, our approach has better resolution and much better interference and clutter rejection capability than the standard DAS-based imaging methods. The excellent performance of the proposed method is demonstrated using experimental data collected via two FLGPR systems recently developed by PSI (Planning Systems, Inc.) and SRI (Stanford Research Institute).     

Leadership for new US strategic directions

Although faced with the new global challenges of terrorism and peer competition, the USA has been slow to adapt its cold war forces, and newer ‘warfighter’ strategy to meet them. Cyberspace and outer space offer the means to do this, via ‘responsive’ microsatellites and low-cost launchers, and broadband internet information and education services. The US military leadership is, however, not well enough versed in these technologies, with senior personnel largely lacking a space or technical background and having little appetite for change. If the USA is successfully to meet current challenges, it must first create a leadership that is technologically capable and philosophically attuned to change.     

Protein crystal growth aboard the U.S. space shuttle flights STS-31 and STS-32.

The first microgravity protein crystal growth experiments were performed on Spacelab I by Littke and John. These experiments indicated that the space grown crystals, which were obtained using a liquid-liquid diffusion system, were larger than crystals obtained by the same experimental system on earth. Subsequent experiments were performed by other investigators on a series of space shuttle missions from 1985 through 1990. The results from two of these shuttle flights (STS-26 and STS-29) have been described previously. The results from these missions indicated that the microgravity grown crystals for a number of different proteins were larger, displayed more uniform morphologies, and yielded diffraction data to significantly higher resolutions than the best crystals of these proteins grown on earth. This paper presents the results obtained from shuttle flight STS-32 (flown in January, 1990) and preliminary results from the most recent shuttle flight, STS-31 (flown in April, 1990).     

Five millinewton field emission thruster testing

A compact cluster of two 80-mm-wide emitters has been designed, built and tested. The field emission thruster using this cluster is able to produce thrust in excess of 5 mN at high mass efficiency.     

The Tracking Index: A Generalized Parameter for ? ? ? and ? ? ? ? Target Trackers

A generalized, optimal filtering solution is presented for the target tracking problem. Applying optimal filtering theory to the target tracking problem, the tracking index, a generalized parameter proportional to the ratio of the position uncertainty due to the target maneuverability to that due to the sensor measurement, is found to have a fundamental role not only in the optimal steady-state solution of the stochastic regulation tracking problem, but also in the track initiation process. Depending on the order of the tracking model, the tracking index solution yields a closed form, consistent set of generalized tracking gains, relationships, and performances. Using the tracking index parameter, an initializing and tracking procedure in recursive form, realizes the accuracy of the Kalman filter with an algorithm as simple as the well-known ? ? ? filter or ? ? ? ? ? filter depending on the tracking order.     

Improved representation of the night and twilight E-region critical frequency

Measurement data from the Malvern, UK incoherent-scatter radar are comparedwith differing IRI and CCIR formulations and proposals offered for the way ahead.     

Dielectric properties and microwave remote sensing

The importance of the dielectric properties of earth, ocean and snow surfaces in microwave remote sensing is reviewed. Data on dielectric properties of materials in the microwave frequency range are very scarce and their behaviour is not fully understood. In this paper the need for dielectric properties of ocean and snow surfaces, the earth's surface and subsurface materials is discussed for the quantitative and qualitative interpretation of microwave remote sensing data of developing countries.