Landsat-4 orbit determination using TDRSS

This paper presents the results of a study to compare the orbit determination accuracy for a Tracking and Data Relay Satellite (TDRS) System (TDRSS)-user spacecraft, Landsat-4, obtained using a Prototype Filter Smoother (PFS), with the accuracy of an established batch-least-squares system, the Goddard Trajectory Determination System (GTDS). The results of Landsat-4 orbit determination provide useful experience for the Earth Observing System (EOS) series of satellites. The filtered and smoothed PFS orbit solutions were compared with the definitive GTDS orbit solutions for Landsat-4; the root-mean-square (RMS) solution difference was 6.6 meters.     

Photometric calibration and first results obtained with the UFT experiment on board the astron satellite

The UV telescope of 30 cm diameter equipped with a three channel scanner spectrometer aboard the highly eccentric orbit space station “ASTRON” is describedAbsolute calibration of the whole device is performed using spectra of standard stars, of which absolute values were obtained by TDI or IUE experiments. Several photometric controls have been made on the stability of the equipment after one year of operation which demonstrate reliability of some first results obtained by the UFT.The sensitivity curve of the spectrophotometric system has been observed with a reproducibility of 2σ = 10% or better.The repeated observation of one star (139 Tau) indicates that the overall performance exhibits the same quality after one year in orbit. The low resolution mode ($\text{Δ λ = 28}\text{A}\text{?}$) leads to a powerful new investigation of faint extended sources.     

Concept of a space telescope able to see the planets and even the satellites around the nearest stars

The Space Telescope will be launched in 1986 and will improve considerably our observational possibilities, but not the visibility of outer planetary systems.The solar system as seen from Alpha Centauri is presented, as well as the nearest stars and the main cameras of the Space Telescope.As a possible improvement the action of a distant and star-shaped screen is described; that screen is 100 to 800 meters and placed 10⁵ to 10⁶ km in front of the telescope; it allows one to avoid the dazzling effect of the stars and to look for planets such as Jupiter and Saturn up to 20 to 40 light-years. Such planets as Earth and Venus are a little less visible.The visibility of satellites such as the Moon is discussed; it remains at the limit of our technical possibilities.This conceptual paper does not consider in detail the technical difficulties involved.     

Design of Switching Regulator with Combined FM and On-Off Control

The design and implementation of a switching regulator incorporating a high-frequency series-resonant converter and a combined FM and on-off feedback control is presented. The combined FM and on-off control results in a better conversion efficiency and a wider range of operational input voltage and output current. A 22.5 V, 50 W experimental regulator has been built to demonstrate the practicality of the circuit and its high efficiency, typically 92 to 96 percent, depending on the input and loading conditions.     

A review of the technical development of concorde

The technical problems encountered during the development and certification of Concorde are reviewed. The topics covered are mainly associated with aerodynamics, but other areas are discussed where they interact with the aerodynamic design or if there were conditions peculiar to supersonic transportation which had to be considered.     

Changes of contractile responses due to simulated weightlessness in rat soleus muscle.

Some contractile and electrophysiological properties of muscle fibers isolated from the slow-twitch soleus (SOL) and fast-twitch extensor digitorum longus (EDL) muscles of rats were compared with those measured in SOL muscles from suspended rats. In suspended SOL (21 days of tail-suspension) membrane potential (Em), intracellular sodium activity (aiNa) and the slope of the relationship between Em and log [K]o were typical of fast-twitch muscles. The relation between the maximal amplitude of K-contractures vs Em was steeper for control SOL than for EDL and suspended SOL muscles. After suspension, in SOL muscles the contractile threshold and the inactivation curves for K-contractures were shifted to more positive Em. Repriming of K-contractures was unaffected by suspension. The exposure of isolated fibers to perchlorate (ClO4-)-containing (6-40 mM) solutions resulted in a similar concentration-dependent shift to more negative Em of activation curves for EDL and suspended SOL muscles. On exposure to a Na-free TEA solution, SOL from control and suspended rats, in contrast to EDL muscles, generated slow contractile responses. Suspended SOL showed a reduced sensitivity to the contracture-producing effect of caffeine compared to control muscles. These results suggested that the modifications observed due to suspension could be encounted by changes in the characteristics of muscle fibers from slow to fast-twitch type.     

Phase gradient autofocus-a robust tool for high resolution SARphase correction

The phase gradient autofocus (PGA) technique for phase error correction of spotlight mode synthetic aperture radar (SAR) imagery is examined carefully in the context of four fundamental signal processing steps that constitute the algorithm. We demonstrate that excellent results over a wide variety of scene content, and phase error function structure are obtained if and only if all of these steps are included in the processing. Finally, we show that the computational demands of the fun PGA algorithm do not represent a large fraction of the total image formation problem, when mid to large size images are involved     

Multidimensional Algebraic Polynomial Approximation

A computational algorithm to approximate an n-dimensional function of the form F(x,y,z, ...) by an algebraic polynomial in the least square (LSQ) sense is described. The basis of this algorithm is that the n-dimensional function can be approximated by a set of polynomials in each one of the independent variables x,y,z, ... . This technique is illustrated by deriving the algebraic polynomial approximation in the LSQ sense for three-dimensional functions of the form F(x,y,z).     

Contactless positioning,manipulation and shaping of liquids by gas bearing for microgravity applications

Contactless positioning, manipulation and shaping of liquids using the gas bearing principle is demonstrated by ground experiments. Extensions to microgravity applications are presented also associated with solidification of molten materials.