Production and action of cytokines in space.

B6MP102 cells, a continuously cultured murine bone marrow macrophage cell line, were tested for secretion of tumor necrosis factor-alpha and Interleukin-1 during space flight. We found that B6MP102 cells secreted more tumor necrosis factor-alpha and interleukin-1 when stimulated in space with lipopolysaccharide than controls similarly stimulated on earth. This compared to increased secretion of interferon-beta and -gamma by lymphocytes that was measured on the same shuttle flights. Although space flight enhanced B6MP102 secretion of tumor necrosis factor-alpha, an experiment on a subsequent space flight (STS-50) found that cellular cytotoxicity, mediated by tumor necrosis factor-alpha, was inhibited.     

Linear Frequency Modulation Derived Polyphase Pulse Compression Codes

Two new polyphase pulse compression codes and efficient digital implementation techniques are presented that are very Doppler tolerant and that can provide large pulse compression ratios. One of these codes is tolerant of precompression bandwidth limitations.     

Vertical distribution of disequilibrium species in Jupiter's troposphere

Sources of organic matter and inorganic tracers on Jupiter, including solar UV photolysis, lightning discharges, and convective quenching of hot gases from the lower atmosphere, are reviewed in light of Earth-based and Voyager data with the purpose of predicting the tropospheric steady-state abundances and vertical distributions of HCN, CH₂O, and other species.It is concluded that a steady-state mole fraction of HCN in the Jovian troposphere of only 10^-12 could be maintained by vertical transport of hot gases from the deep atmosphere. The observed HCN abundance (roughly X_HCN = 10^-9) appears to be due to photochemical reactions.After HCN, the most abundant organic disequilibrium species in the troposphere is probably C₂H₆, derived from direct photolysis of CH₄ at high altitudes, with a mole fracton of 10^-10 at the H₂O cloud level. Inorganic tracers of disequilibrium processes are also briefly summarized.     

Mission-oriented theory for ISTP

The goal of mission-oriented theory is to develop techniques and models which can be used by experimentalists and theorists to interpret spacecraft measurements, deducing from them the maximum amount of information about both local and large-scale dynamics. To be effective, theorists and experimentalists must express their results in a common format. A reasonable starting point is for mission theorists to adopt the format currently used by experimentalists. To this end we have developed new diagnostics for plasma kinetic simulations, which display the results in formats very similar to those commonly used to present satellite wave and particle measurements. We have used a simulation of broadband electrostatic noise to demonstrate how, by comparing simulation results with observations, we can infer quantities which cannot be measured, such as the wave mode. We are also developing the capability of creating data streams from virtual spacecraft located in the simulation region. For example, we used a kinetic magnetopause simulation to explore the ways in which simulations can assist in the interpretation of single and multiple satellite measurements in regions of strong spatial inhomogeneity. To address directly the mission objective of measuring global transport, global MHD models are employed. In order to facilitate the initial comparison with ISTP satellites, time histories of simulated generic states of the magnetosphere will be stored on optical disks; these will then be used to create dynamical displays of both local parameters and the global configuration. Finally we demonstrate the use of data based phenomenological magnetic field models in single particle trajectory calculations to describe large-scale kinetic properties of the magnetospheric plasma. We briefly discuss the success of large-scale kinetic calculations in delineating the structure of the plasma sheet, and present some possible ISTP research initiatives which can be used to determine the structure of the very distant tail and the entry of plasma into the tail.     

Adaptive Resource Allocation in a Spatial Spectral Processor

A method for achieving an optimal allocation of fixed computational resources in a spatial/spectral filtering system is developed. Specifically, clock cycles per unit time for a given processor are to be optimally allocated. The system is a cascade of three subsystems: an adaptive beamformer, a bandpass filter, and a spectral whitener. Each subsystem has adjustable parameters which are related to required arithmetic operations. A gradient projection algorithm is used to find a best allocation according to specified criteria. Two simulation examples are presented to show how the algorithm operates and to indicate the kind of improvement that is possible in a system design.     

Rapid impactor sample return (RISR) mission scenario

Due to the long lead time and great expense of traditional sample return mission plans to Mars or other astronomical bodies, there is a need for a new and innovative way to return materials, potentially at a lower cost. The Rapid Impactor Sample Return (RISR) mission is one such proposal. The general mission scenario involves a single pass of Mars, a Martian moon or an asteroid at high speeds (7 km/s), with the sample return vehicle skimming just 1 or 2 m above a high point (such as a top ridge on Olympus Mons on Mars) and releasing an impactor. The impactor strikes the ground, throwing up debris. The debris with roughly the same forward velocity will be captured by the sample return vehicle and returned to Earth. There is no delay or orbit in the vicinity of Mars or the asteroid: RISR is a one-pass mission. This paper discusses some of the details of the proposal. Calculations are presented that address the question of how much material can be recovered with this technique. There are concerns about the effect of Mars tenuous atmosphere. However, it will be noted that such issues do not occur for RISR style missions to Phobos, Deimos, or asteroids and Near Earth Objects (NEOs). Recent test results in the missile defense community (IFTs 6–8 in 2001, 2002) have scored direct hits at better than 1 m accuracy with closing velocities of 7.6 km/s, giving the belief that accuracy and sensing issues are developed to a point that the RISR mission scenario is feasible.     

Magnetic Fields of the Satellites of Jupiter and Saturn

This paper reviews the present state of knowledge about the magnetic fields and the plasma interactions associated with the major satellites of Jupiter and Saturn. As revealed by the data from a number of spacecraft in the two planetary systems, the magnetic properties of the Jovian and Saturnian satellites are extremely diverse. As the only case of a strongly magnetized moon, Ganymede possesses an intrinsic magnetic field that forms a mini-magnetosphere surrounding the moon. Moons that contain interior regions of high electrical conductivity, such as Europa and Callisto, generate induced magnetic fields through electromagnetic induction in response to time-varying external fields. Moons that are non-magnetized also can generate magnetic field perturbations through plasma interactions if they possess substantial neutral sources. Unmagnetized moons that lack significant sources of neutrals act as absorbing obstacles to the ambient plasma flow and appear to generate field perturbations mainly in their wake regions. Because the magnetic field in the vicinity of the moons contains contributions from the inevitable electromagnetic interactions between these satellites and the ubiquitous plasma that flows onto them, our knowledge of the magnetic fields intrinsic to these satellites relies heavily on our understanding of the plasma interactions with them.