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).     

Magnetic holes in the solar wind and their relation to mirror-mode structures

Data obtained by the Ulysses magnetometer and solar wind analyzer have been combined to study the properties of magnetic holes in the solar wind between 1 and 5.4 AU and to 23° south latitude. Although the plasma surrounding the holes was generally stable against the mirror instability, there are indications that the holes may have been remnants of mirror mode structures created upstream of the points of observation. Those indications include: (1) For the few holes for which proton or alpha-particle pressure could be measured inside the hole, the ion thermal pressure was always greater than in the plasma adjacent to the holes. (2) The plasma surrounding many of the holes was marginally stable for the mirror mode, while the plasma environment of all the holes was significantly closer to mirror instability than was the average solar wind. (3) The plasma containing trains of closely spaced holes was closer to mirror instability than was the plasma containing isolated holes. (4) The near-hole plasma had much higher ion (ratio of thermal to magnetic pressure) than did the average solar wind.     

The WIND magnetic field investigation

The magnetic field experiment on WIND will provide data for studies of a broad range of scales of structures and fluctuation characteristics of the interplanetary magnetic field throughout the mission, and, where appropriate, relate them to the statics and dynamics of the magnetosphere. The basic instrument of the Magnetic Field Investigation (MFI) is a boom-mounted dual triaxial fluxgate magnetometer and associated electronics. The dual configuration provides redundancy and also permits accurate removal of the dipolar portion of the spacecraft magnetic field. The instrument provides (1) near real-time data at nominally one vector per 92 s as key parameter data for broad dissemination, (2) rapid data at 10.9 vectors s^–1 for standard analysis, and (3) occasionally, snapshot (SS) memory data and Fast Fourier Transform data (FFT), both based on 44 vectors s^–1. These measurements will be precise (0.025%), accurate, ultra-sensitive (0.008 nT/step quantization), and where the sensor noise level is <0.006 nT r.m.s. for 0–10 Hz. The digital processing unit utilizes a 12-bit microprocessor controlled analogue-to-digital converter. The instrument features a very wide dynamic range of measurement capability, from ±4 nT up to ±65 536 nT per axis in eight discrete ranges. (The upper range permits complete testing in the Earth's field.) In the FTT mode power spectral density elements are transmitted to the ground as fast as once every 23 s (high rate), and 2.7 min of SS memory time series data, triggered automatically by pre-set command, requires typically about 5.1 hours for transmission. Standard data products are expected to be the following vector field averages: 0.0227-s (detail data from SS), 0.092 s (detail in standard mode), 3 s, 1 min, and 1 hour, in both GSE and GSM coordinates, as well as the FFT spectral elements. As has been our team's tradition, high instrument reliability is obtained by the use of fully redundant systems and extremely conservative designs. We plan studies of the solar wind: (1) as a collisionless plasma laboratory, at all time scales, macro, meso and micro, but concentrating on the kinetic scale, the highest time resolution of the instrument (=0.022 s), (2) as a consequence of solar energy and mass output, (3) as an external source of plasma that can couple mass, momentum, and energy to the Earth's magnetosphere, and (4) as it is modified as a consequence of its imbedded field interacting with the moon. Since the GEOTAIL Inboard Magnetometer (GIM), which is similar to the MFI instrument, was developed by members of our team, we provide a brief discussion of GIM related science objectives, along with MFI related science goals.     

Interplanetary type III radio bursts observed simultaneously by ICE

We analyze two solar type III radio bursts that were observed simultaneously by the ICE and Ulysses spacecraft. Both bursts originated behind the solar limb as viewed from either spacecraft. At the time of these events, ICE was in the ecliptic plane at 1 AU and Ulysses was 35° south of the ecliptic plane at 4 AU. For one event on 931117, the ratios of the peak flux densities measured at each spacecraft, at each observing frequency, were consistent with the most probable source locations relative to ICE and Ulysses. The second event on 931004 was a complex burst consisting of two distinct components at high frequencies. At low frequencies, the intensity of the first component decreased rapidly at each spacecraft. The second component, however, dominated the low frequency emission observed at Ulysses but not at ICE. These differences in the observed radiation must be related to the different viewing geometries of the two spacecraft. The measured onset times as a function of observing frequency were consistent with a constant exciter speed through the interplanetary medium and suggest that there are significant propagation delays, especially for the radiation propagating within the ecliptic plane.     

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).