Clutter metrics for target detection systems

The problem of calculating an effective contrast for diffused targets in visual scenery is addressed. The effect of local variations of intensity in the vicinity of the target is modeled by considering the distribution of the intensity of the edges. The effect of global clutter is discussed from the vantage point of selecting the best model for background scenery. Generalized contrast measures are described and applied to real scenes     

Cloud profiling radar for the CloudSat mission

The Cloud Profiling Radar (CPR) for the upcoming CloudSat Mission is a spaceborne 94-GHz nadir-looking radar that measures the power backscattered by clouds as a function of distance from the radar. This sensor is expected to provide cloud measurements at a 500-m vertical resolution and a 1.5 km horizontal resolution. CPR will operate in a short-pulse mode and will yield measurements at a minimum detectable sensitivity of -28 dBZ.     

Rotational maneuver of nonlinear uncertain elastic spacecraft

The question of attitude control and elastic mode stabilization of a spacecraft (orbiter) with beam-tip-mass-type payloads is considered. A three-axis moment control law is derived to control the attitude of the spacecraft. The derivation of the control moments acting on the spacecraft does not require any information on the system dynamics. The control law includes a reference model and a dynamic compensator in the feedback path. For damping out the elastic motion excited by the slewing maneuver, an elastic mode stabilizer is designed. The stabilization is achieved by modal velocity feedback using force and torque actuators located at the payload end of the elastic beam. Collocated actuators and sensors provide robust stabilization. Simulation results are presented to show that rotational maneuvers and vibration stabilization can be accomplished in the closed-loop systems despite the presence of model uncertainty and disturbance torque in the system     

Efficient numerical algorithm for steady-state Kalman covariance

A stable, quadratically convergent numerical algorithm is presented for computing the steady-state covariance and gain matrices of the Kalman filter. The method is more rapidly convergent than standard Riccati integration techniques and is easier to implement than existing eigenvalue-eigenvector algorithms. The quadratic convergence is proved analytically and illustrated by a numerical example     

Development of a CELSS bioreactor: oxygen transfer and micromixing in parabolic flight.

The gas exchange portion of a phase-separated loop bioreactor was tested with respect to oxygen mass transfer and micromixing in accelerations of 0.01g, 1g, and 2g. A plot of the overall mass transfer coefficient versus gravity indicates the rate of oxygen transfer does not change as a function of acceleration. Also, it was determined that the micromixing did not exhibit significant changes in the various gravitational fields. These observations indicate the loop bioreactor should function independent of acceleration.     

Processing requirements for multisensor low-cost brilliantmunitions

A generic mission for an autonomous brilliant munition is presented and used to identify the functions that embedded signal processors must perform. Based on these functions and other operational factors such as weather, countermeasures, larger search areas, reduced false alarm rates, and increased munition maneuverability, the processing loads in bits/second messages/second, operations/second, and instructions/second are derived. An evaluation of general implementation issues such as the requirements for data fusion, distributed and parallel processing architectures, reliable software, and low-cost hardware is presented     

Latitudinal asymmetry in electron and ion density distribution in southern and northern hemispheres

With data of satellite INTERCOSMOS-BULGARIA-1300 northern and corresponding southern hemisphere plasma densities have been compared. Southern densities are greater in the ?90 to ?180 and +30 to +120° ranges. The opposite is true for ?60 to +30°. No asymmetry has been observed during daytime. These results are explained by the variations of the magnetic declination.     

The loneliness of the long-duration astronaut

This paper investigates the psychological implications of long duration spaceflight. Initial psychological problems associated with a heavy workload were identified during Skylab missions. Since then, most of our knowledge of psychological problems has come from experience onboard Russian spacecraft. Noted problems include anxiety, boredom, crew interactions, problems associated with isolation and confinement, and others. Efforts to alleviate or prevent these problems are discussed, as well as comparisons to similar environments such as arctic regions or submarines. As the U.S. participates in longer space missions, it will be wise to study psychological issues and to learn from our Russian counterparts.     

The pleurodele, an animal model for space biology studies.

Pleurodeles waltl, an Urodele amphibian is proposed as a model for space biology studies. Our laboratory is developing three types of experiments in space using this animal: 1) in vivo fertilization and development ("FERTILE" project); 2) influence of microgravity and space radiation on the organization and preservation of specialized structures in the neurons and muscle cells (in vitro; "CELIMENE" PROJECT); 3) influence of microgravity on tissue regeneration (muscle, bone, epidermis and spinal cord).     

Solar wind charge states measured by ULYSSES/SWICS in the south polar hole

The Ulysses mission now has an extensive data base covering several passes of the south polar coronal hole as the spacecraft proceeds to higher latitudes. Using composition measurements from the SWICS experiment on the Ulysses spacecraft, we have obtained charge state distributions, and hence inferred coronal ionization temperatures, for several solar wind species. In particular, we present an overview of Oxygen ionization temperature measurements, based on the O⁷⁺/O⁶⁺ ratio, for the period January 1993 until April 1994 (23°S to 61°S heliographic latitude), and detailed Oxygen, Silicon and Iron charge state distributions of the south polar hole during a two month period of nearly continuous hole coverage, Dec 1993–Jan 1994 (45°S to 52°S heliographic latitude).