Southwest Research Institute 2001 Annual Report, Space Science

Space science and engineering are areas of vigorous activity at SwRI. Institute scientists and engineers collaborate on the design and fabrication of innovative scientific instruments, spacecraft computers, and power supplies for flight on Earth-orbiting spacecraft, interplanetary probes, and sounding rockets. Strong theoretical and observational research programs are maintained in solar and heliospheric physics, space physics, planetary science, and stellar astronomy.

Well into its second year of operation, the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft continues to provide new insights into the structure and dynamics of the near-Earth space environment. Among the achievements of the mission are the first global images of the ring current, the plasmasphere, and the proton aurora, as well as the observation of solar wind and interstellar neutrals inside the Earth's magnetosphere. SwRI scientists and the IMAGE team members are using mission data to investigate a variety of phenomena, including previously unobserved structures in the plasmasphere, detached proton precipitation regions revealed by the auroral imager, and the injection of plasma into the inner magnetosphere during magnetospheric disturbances. In addition to their use in scientific studies, the Space Environment Center of the National Oceanic and Atmospheric Administration is using real-time auroral images from the spacecraft for space weather forecasting. SwRI leads the IMAGE science investigation and is responsible for overall mission management. The mission has been extended until October 2005.

The NASA Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) mission will place two spectrometers on two high-altitude spacecraft to image stereoscopically the neutral atoms created from the ions that play a dominant role in magnetospheric disturbances. The first of the neutral-atom imagers, developed by SwRI, Los Alamos National Laboratory, and the Aerospace Corporation, was successfully calibrated at the Institute this year. Launch of the first spacecraft is scheduled for 2003, and the second spacecraft is expected to launch in 2005. In addition to leading the overall investigation, SwRI is providing the detectors, high-voltage power supplies, and front-end electronics for the TWINS imagers.

Institute research has focused recently on heliospheric physics - the study of the charged particles and fields of solar origin that populate interplanetary space. Institute scientists are analyzing solar wind data acquired with science instruments on board the Ulysses spacecraft and the Advanced Composition Explorer (ACE) spacecraft. Since its launch in 1990, Ulysses has provided an unprecedented look at the solar wind at both high and low latitudes and has tracked its evolution over an entire solar cycle, revealing striking differences between the solar wind structure observed during the declining phase of the cycle and that observed as the sun approaches its activity peak. Stationed at the Lagrange point 1.5 million kilometers upstream from the Earth, ACE is the nation's primary solar wind monitor for both scientific and space weather applications.

SwRI scientists are studying the relationship between the sun's complex, ever-changing magnetic field and the ultrahot (million-degree) plasma of the solar corona. The work, funded by NASA, uses a unique SwRI-developed technique called "fluxon analysis" to solve problems inaccessible to more conventional techniques. This computer simulation method will ultimately enable forecasting of solar coronal mass ejections, which when directed earthward can trigger geomagnetic storms.

Institute researchers are collaborating with colleagues at several institutions to analyze images of jovian auroral X-ray emissions acquired with the Earth-orbiting Chandra X-Ray Observatory in conjunction with a Cassini flyby of Jupiter in December 2001. Coordinated analysis of the Chandra X-ray data, of simultaneous Hubble Space Telescope auroral images at far-ultraviolet wavelengths, and of in situ particles-and-fields data acquired by the Cassini and Galileo spacecraft, is expected to yield important new insights into the complex magnetospheric processes that drive the jovian aurora.

SwRI scientists are developing computer models of the early climate of Mars to understand how liquid water may once have flowed on its surface. These models are the first to incorporate the greenhouse effects of gases and carbon dioxide clouds that may have existed in the early martian atmosphere. By combining the effects of gas exchanges with the surface, polar cap evolution, and gases lost to space, these models may ultimately reveal if and how Mars was hospitable to life early in its history. SwRI researchers also have been studying the climate effects of large comet impacts on the planet Venus. They find that very large comets, by injecting significant quantities of water (a greenhouse gas) into the atmosphere, can trigger substantial global warming on Venus.

Institute scientists are contributing to the European Space Agency (ESA) Mars Express mission as members of the ultraviolet spectrometer team and of the Swedish ASPERA-3 instrument team. The ASPERA instrument is designed to study the interaction of the martian atmosphere with the solar wind. Because Mars lacks a strong intrinsic magnetic field, it has no magnetosphere to shield it from solar wind particles, which impinge directly on the planet's upper atmosphere. Theoretical studies indicate that the loss of atmospheric material resulting from this interaction has played a significant role in evolution of the martian atmosphere and climate. The Institute is providing the electron spectrometer (ELS) component of the ASPERA experiment. The ELS flight unit was delivered in late 2001 to the Swedish Institute of Space Physics in Kiruna for integration with the ASPERA instrument suite, which comprises a neutral-atom imager as well as neutral and charged particle detectors. Mars Express is scheduled for launch in 2003.

Smooth particle hydrodynamic (SPH) simulations, which enable complex calculations of impact phenomena, are utilized at SwRI to model lunar formation in the so-called "giant impact" hypothesis for lunar origin. SwRI scientists recently demonstrated for the first time that a single impact is capable of accounting for the main characteristics of the current Earth-Moon system. Scientists are also applying SPH methods to the origin of the Pluto-Charon binary planet pair and to the formation of asteroid satellites. Institute scientists investigating the earliest history of the Earth and other planets use these sophisticated numerical hydrodynamic models to simulate collisions between planet-sized objects, believed to have been typical in the late stages of planet formation in our solar system.

Institute scientists are heavily involved in the theoretical and observational study of small solar system bodies such as comets, asteroids, Kuiper Belt Objects, and planetesimals. In the area of comet research, SwRI researchers have developed models of the behavior of certain key chemical species in the comas (atmospheres) of comets Hyakutake and Hale-Bopp. They are also developing theoretical models for gas effusion from cometary nuclei that will be tested by the Microwave Rosetta Orbiter (MIRO) instrument on the ESA Rosetta mission to Comet Wirtanen. In addition, the Institute is furnishing two instruments for the Rosetta mission. ALICE is an ultraviolet spectrometer designed to study the release of gases from the comet nucleus. The Ion and Electron Spectrometer (IES) is an in situ instrument developed to measure comet Wirtanen's charged particle environment and to study its interaction with the solar wind. Both instruments have been delivered for integration on the Rosetta spacecraft. Launch is scheduled for 2003, with the comet rendezvous occurring in 2011.

Institute scientists are participating in the study of near-Earth objects (NEOs) - comets or asteroids with orbits that bring them close to the Earth and which present a potential impact threat to the planet. SwRI researchers helped organize the first international workshop on properties of potentially hazardous cosmic objects and helped develop a roadmap for determining the geophysical properties of NEOs. In addition, an SwRI-led team of U.S. and French researchers is carrying out an observational and computer-based study of NEOs that will better quantify the likelihood of future catastrophic collisions with Earth. The study will also help observational astronomers to improve their search for NEOs that are too small, too dark, or with orbits that make them difficult to find.

SwRI is providing command and data handling and power interface assemblies for the NASA Deep Impact mission, a Discovery-class mission to comet Tempel 1. The mission consists of a flyby spacecraft and an impactor. The impactor will collide with the comet nucleus, exposing pristine material from the comet's interior, while the impact is observed with instruments on board the spacecraft. By studying the unprocessed material from the comet's interior, scientists hope to obtain information about the early history of the solar system. SwRI will provide space-qualified electronic assemblies for the two spacecraft that will be responsible for attitude control, spacecraft health, and instrument data collection. Deep Impact is scheduled for launch in January 2004, with the comet encounter occurring in early July 2005.

Using internal research funding, Institute engineers addressed problems associated with power sensitivity and alignment errors in remotely operated astronomical telescopes. Electronic and structural noises, which are inadvertently introduced into all telescopic hardware, degrade the hardware's precision and alignment. Although instrument devices correct for noise-caused deviations, they rely on digital information to process and send corrective signals to the instrument hardware. Digital logic must follow a restricted linear set because of computational restrictions. SwRI engineers developed new nonlinear filtering algorithms, with a gimbaled, laser-pointing experiment to test the hardware. With these nonlinear filtering techniques, Institute engineers observed a 20 percent decrease in error over the conventional approach under the same disturbance and noise environment. In addition, with stability as the primary objective and slightly lower performance, this method demonstrated a decrease in energy requirements by as much as 74 percent over the conventional approach.

Copyright© 2002 by Southwest Research Institute. All rights reserved under U.S. Copyright Law and International Conventions. No part of this publication may be reproduced in any form or by any means, electronic or mechanical, including photocopying, without permission in writing from the publisher. All inquiries should be addressed to Communications Department, Southwest Research Institute, P.O. Drawer 28510, San Antonio, Texas 78228-0510, phone (210) 522-2257, fax (210) 522-3547.