Space Sciences

Research in space science and the development of innovative spacecraft instrumentation and systems continue to be vigorous activities at SwRI. Institute scientists work in close collaboration with engineering and technical staff on the design and fabrication of miniaturized scientific instruments, spacecraft computers, and power supplies for flight on interplanetary probes, Earth-orbiting spacecraft, and sounding rockets. Strong theoretical and observational research programs are maintained in the fields of space physics, planetary science, stellar astronomy, and solar physics.

The IMAGE spacecraft structure is shown undergoing modal testing at Lockheed Martin Missiles and Space prior to the installation of the solar panels. Lockheed Martin is the subcontractor selected by SwRI to build the spacecraft.

Under the Institute's leadership, the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) mission is on its way toward a January 1, 2000 launch. Development of the scientific payload is nearing completion, with environmental testing of the scientific instruments and spacecraft subsystems scheduled for the fall of 1998. In early 1999, the science instruments will be delivered to SwRI for payload integration, functional testing of the complete payload, and electromagnetic compatibility testing. Selected in 1996 as the principal investigator institution for IMAGE, SwRI leads a team of investigators from 14 institutions. In addition to its overall responsibility for managing development of the IMAGE satellite, which will provide the first global images of key regions of the Earth's magnetosphere, SwRI is building one of the neutral atom imagers and the central instrument data processor, through which the instruments will communicate with the spacecraft and the ground.

Since the Cassini spacecraft was launched in October 1997, Institute scientists have been heavily involved in operations planning for the Cassini Plasma Spectrometer (CAPS) and the Ion and Neutral Mass Spectrometer (INMS) investigations, as well as calibration of the engineering models of both instruments. This calibration will be used to refine and extend data acquired during flight instrument calibration -- critically important for instrument programming and data analysis activities that occur prior to Cassini's arrival at Saturn in July 2004. Important milestones on Cassini's journey are instrument checkout and commissioning in January 1999 and the Venus and Earth flybys in June and August, respectively. By the time of the Earth encounter, which will add speed to the spacecraft through a "slingshot" effect from Earth's gravity, Cassini will have traveled roughly 900 million miles through the inner solar system and will be on the final leg of its two-billion-mile voyage to Saturn. The INMS instrument will not operate until Cassini reaches the Saturn system. However, CAPS will run during the Venus and Earth encounters, allowing unique calibration data to be acquired in the space environments of the two planets. SwRI is the principal investigator institution for CAPS, which was developed by an international consortium under SwRI leadership, and the science team leader for the INMS instrument, developed at NASA's Goddard Space Flight Center. Cassini carries sophisticated sensors to support 27 investigations that will probe the mysteries of the Saturn system.

The Deep Space 1 spacecraft carrying the Plasma Experiment for Planetary Exploration (PEPE), a time-of-flight ion mass spectrometer developed by SwRI in collaboration with Los Alamos National Laboratory, was launched in late October from Cape Canaveral, Florida. PEPE incorporates the essential performance features of the Saturn-bound CAPS instrument, but in a package that requires less than 30 percent of the mass and 50 percent of the power of CAPS. This dramatic reduction in mass and power was achieved through innovative ion and electron optics, the wide use of electroplated plastics, and novel electronics architecture and packaging. PEPE is one of only two science instruments aboard the Deep Space 1 spacecraft, in the first mission to be conducted under NASA's New Millennium Program. During its mission, Deep Space 1 will carry out flybys of an asteroid and a comet. Three SwRI scientists were selected to analyze the scientific data acquired during these encounters.

The Plasma Experiment for Planetary Exploration (PEPE), a miniaturized, lightweight plasma spectrometer developed by SwRI in collaboration with the Los Alamos National Laboratory for the Deep Space 1 mission, is shown during final testing before the spacecraft's October 1998 launch.

SwRI is providing two instruments for a European comet mission. The SwRI-developed Ion and Electron Spectrometer (IES), which is related to the PEPE instrument, and ALICE ultraviolet spectrograph will be launched in 2003 as part of the European Space Agency (ESA) Rosetta mission to comet Wirtanen. Detailed design activities are under way. ALICE will acquire spectral data on Wirtanen at far-ultraviolet wavelengths, providing information on noble gas abundances in the nucleus, atomic abundances in the coma, major ion abundances in the tail, and the production rates and distribution of water, carbon dioxide, and carbon monoxide. IES will measure the effects on the comet of the solar wind and solar ultraviolet radiation. In addition to IES and ALICE, SwRI is supplying the waveform capture subsystem for a sensor in the ROSINA instrument being developed by the University of Bern, Switzerland.

SwRI provided the Spectrometer Electronic System for the neutron, gamma ray, and alpha particle spectrometers developed by Los Alamos National Laboratory for the NASA Lunar Prospector mission, launched in January 1998. The system, which was designed, fabricated, and tested at SwRI, consisted of high- and low-voltage power supplies and the digital electronics that acquire and format the spectrometer data and send them to the spacecraft computer for transmission to Earth. Lunar Prospector entered low polar orbit around the Moon in mid-January 1998 and began acquiring data on lunar composition, gravity, and crustal magnetism. The neutron spectrometer has gathered data providing the first definitive evidence for the presence of water ice in permanently shadowed crater bottoms at both the north and south lunar poles.

SwRI engineers designed and built the pyro command timer for the Lunar Prospector trans-lunar-injection stage. The device commanded the firing of the spin rockets, main engine burn, and spacecraft switch-on. In addition, the timer controlled the Prospector's release from the Athena 2 launch vehicle into the trajectory that took it to the moon in January.

As the two-year Galileo Europa mission -- an extension of the Galileo orbital mission to Jupiter -- nears its halfway mark, SwRI scientists continue to analyze the crater populations on Europa, as well as jovian moons Ganymede and Callisto, for information about the histories of the Galilean moons and the nature of the comet population responsible for cratering in the Jupiter system. Europa's small number of impact craters indicates that its surface is relatively young, compared with the heavily cratered surfaces of Ganymede and Callisto, and suggests that Europa has recently been -- and may still be -- geologically active.

Institute scientists continue to be heavily involved in the analysis of data from the Solar and Heliospheric Observatory (SOHO) mission, sponsored by ESA and NASA. It has long been known that the high-speed solar wind, the supersonic stream of charged particles flowing out from the sun, originates in coronal holes, regions where the solar magnetic field is open. Using SOHO data, SwRI scientists have obtained the first clear evidence of the detailed three-dimensional structure of the source region of the high-speed solar wind. Results of their analysis show that the high-speed solar wind is rooted in the detailed structure of the chromospheric magnetic network, a "honeycomb" pattern formed by the footprints of the sun's magnetic field lines, and that it emanates from localized regions along boundaries and boundary intersections of small-scale magnetic network cells.

Images of the sun's atmosphere, or corona, obtained by SwRI scientists during the total eclipse of the sun in February 1998, show "Bailey's beads" - bright points of light formed immediately before totality by the transmission of sunlight between the mountains on the moon - and open and closed, loop-like corona structures formed by magnetic field lines emerging from the sun's surface. By investigating the behavior of such structures, Institute researchers seek to understand the role of the solar magnetic field in controlling the state and dynamics of the corona.

Planetary formation within our own solar system, as well as in planetary systems around other stars, is an active area of research at SwRI. Using numerical simulation techniques, Institute scientists have constructed a computer model of extra-solar planetary systems to investigate the influence of giant outer planets on the formation of habitable, Earth-like planets in the inner regions of a solar system. In addition, SwRI researchers are performing large-scale computer simulations that seek to describe the origins of the terrestrial planets in our solar system and to investigate the circumstances surrounding the origin of the Earth-moon system, which is believed to have formed as a result of a large impact event between the Earth and a Mars-sized body. Such studies are facilitated by a new computer algorithm developed at SwRI that enables direct simulation of the last stages of planet formation, allowing for determination of final planetary orbits, sizes, rotation rates, and axial tilts.

In collaboration with NASA, SwRI researchers are pioneering the use of high-performance, two-seater aircraft for conducting astronomical research. Using a variant of SwRI's successful Southwest Ultraviolet Imaging System (SWUIS) shuttle imager called SWUIS-A, missions have already been flown in WB-57 and F-18 aircraft from the NASA fleet. Results indicate that, for some applications, these unique astronomical platforms can achieve excellent results at much lower cost than can be achieved using conventional, large aircraft.

SwRI engineers recently developed the Miniaturized Electrostatic Dual top-hat Spherical Analyzer, or MEDUSA™. A combined ion and electron electrostatic analyzer, with a mass of 1.5 kilograms and a power requirement of only 4 watts, MEDUSA will be flown in 1999 on the Swedish microsatellite Astrid-2 and on MUNIN, a Swedish "nanosatellite" that is roughly the size of a shoe box and has a 6 kg mass. MEDUSA measures ion and electron energy distributions in the Earth's auroral magnetosphere.

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