SwRI's Extreme Ultraviolet Spectrograph sounding rocket payload, weighing over 400 pounds, was lofted on its fifth flight on 29 March 1997 to observe comet Hale-Bopp. The instrument performed perfectly, and produced a state-of-the-art spectrum of the comet revealing many new spectral emission features. EUVS has now flown to observe Hale-Bopp, Venus (twice), the Shoemaker-Levy 9 impacts on Jupiter, the lunar atmosphere, and a variety of stellar targets. Since SwRI began operating this instrument in 1994, EUVS's spectral resolution has been increased 10-fold, and its sensitivity has been tripled.
Institute scientists also launched a sounding rocket on May 15, 1997 to study the outer atmosphere of the Sun and solar wind. The rocket payload consisted of two ultraviolet spectrometers and four EUV imagers, using new multi-layer mirror technology, to measure the Helium abundance in the corona and study the acceleration processes of the solar wind. This rocket flight was the cornerstone of an international campaign involving spacecraft and ground-based observatories from around the world. All of the instruments worked perfectly, with high signal-to-noise spectra and images, including the first full disk image of the Sun in the intense ultraviolet light of Hydrogen Lyman-alpha since the Skylab mission in the mid-1970's.
Division 15 is finalizing detailed design work on the ALICE Ultraviolet Spectrometer for the ESA/NASA Rosetta comet Orbiter mission. ALICE was confirmed for flight aboard Rosetta in mid-1997. During 1998 and 1999, SwRI scientists and engineers will build two ALICE prototypes, a flight unit, and a flight spare. This miniaturized, high-tech spectrometer packs into a 3 kg, 3 watt package the kind of scientific power that only instruments weighing 10 to 15 kg and consuming tens of watts usually do. ALICE is one of three US instruments flying aboard the Rosetta comet orbiter. The other two instruments are a JPL/French microwave sounder called MIRO, and a plasma package which includes a SwRI-supplied electron spectrometer (PI, Jim Burch).
During the past year, SWRI scientists have been significant contributors to the NASA Galileo Orbiter mission which has been intensively studying the moons of Jupiter. As members of the Imaging Team, Institute scientists have been investigating the geology of Europa, Ganymede, and Callisto. A focus has been studies of the crater populations on the satellites, and implications for the extreme youth of Europa and active degradational processes on the other satellites, as well as implications for the impactor populations of asteroids and comets. Planning has already begun for the follow-on two-year Galileo Europa mission that begins following conclusion of the nominal two-year orbital tour in December 1997.
SWRI scientists are also significant contributors to the international Solar and Heliospheric Observatory (SOHO) mission, a joint ESA/NASA mission launched on December 2, 1995 to study the Sun. Located in a halo orbit around the Lagrangian L1 point, a gravitational equilibrium between the Earth and the Sun, SOHO provides the first uninterrupted view of the Sun to study its complex magnetic activity, and its interaction with the Sun-Earth environment. As Co-Investigators with the SUMER Ultraviolet Spectrometer experiment on SOHO, institute scientists are helping to discover important clues to the acceleration mechanisms of the high speed solar wind and the detailed structure of its source regions, called coronal holes, which are open magnetic field regions located at the solar poles.
SWRI scientists have spent the last year preparing for the serendipitous encounter of the Near Earth Asteroid Rendezvous spacecraft with the asteroid Mathilde. In late June 1997, NEAR's multi-spectral imager acquired more than 500 images of Mathilde during its successful fly-by. Institute scientists measured the crater population and found that smaller craters resemble the equilibrium crater population on the asteroid Ida, but that larger craters, approaching or exceeding the radius of Mathilde, are unexpectedly numerous. Another surprising result is that Mathilde's mass (measured from radio science experiments) is approximately one-third of what was expected, implying a very low density for the asteroid, which poses intriguing questions about the asteroid's composition. Planning is beginning in earnest for NEAR's year-long orbital studies of Eros.
SwRI planetary scientists are working with JPL artificial intelligence engineers to develop smart software to fly aboard future planetary missions. This project should allow future fly-by and orbiter spacecraft to react in near real-time to data they collect, making decisions much like a scientist would on the basis of the observations. The potential for this kind of software is revolutionary, allowing spacecraft to follow up on exciting discoveries like new satellites, unexpectedly interesting terrains, or new atmospheric emission features. In the past, such follow-up observations were impossible.
Also during the past year, Institute scientists have published paradigm-breaking work, based on Galileo's fly-bys of the asteroids Gaspra and Ida, invoking "space weathering" as a significant process to be considered in the interpretation of reflectance spectra of asteroids. Institute scientists have also been asked to participate in a workshop on interactions between scientists and public policy concerning natural hazards, such as impact of asteroids and comets, and have given a briefing on impact hazard to Congressman David Skaggs at SWRI's Boulder office in April. SWRI scientists are also involved in interpreting both spacecraft and ground-based observations of the crash of comet Shoemaker-Levy 9 into Jupiter in 1994.
Planetary scientists at SwRI made observations of small asteroid-like objects in the outer solar system, in the region of the Kuiper belt. Objects in the Kuiper belt are remnants of the formation of the solar system and can provide information on the conditions during that epoch, and on the formation of the giant gas planets. Observations were made at the MDM telescope on Kitt Peak, and were extremely successful, allowing SwRI scientists to secure a position in observational research of Kuiper belt objects. During the same observing run, the scientists also discovered a comet-like coma around a distant object previously thought to be an asteroid.
Astronomers in Division 15 are working on an array of projects dealing with the evolution of very massive stars (stars from 10 to 100 times the mass of the Sun). They are studying these stars in nearby galaxies (called the Magellanic Clouds) using data from NASA's Ultraviolet Imaging Telescope. According to most theories of star formation and evolution, massive stars should be clumped together in tight groups, but these new data indicate that they are more widely distributed throughout the galaxies than previously expected. Since these stars eventually end their lives in supernova explosions, such a wide distribution of stars can more widely deposit energy and processed material and "stir up" the interstellar medium throughout the galaxy.
Other studies of massive stars are being conducted by SwRI using the Hubble Space telescope: the galaxy M 33, a beautiful spiral galaxy much like our own Milky Way, contains many clusters of massive stars. HST observations of these clusters in visible and ultraviolet light are searching for variations of how massive stars are formed as a function of their position in the galaxy. These data can tell us how dependent the formation of stars is on their local environment.
Division 15 researchers have also presented theoretical work on stars called Luminous Blue Variables (LBVs), which are hot, massive stars that can suddenly increase their brightness and blow off a significant fraction of their atmosphere. These stars are very rare, only a couple dozen of these stars are known, but represent an important and brief (a few hundred thousand years) portion of the life of a massive star. Statistical analyses of the distribution of these stars indicate that they may evolve from a smaller subset of massive stars than suggested by stellar evolution theory. This, in turn, affects the expected number of stars that will explode as supernovae and ultimately become black holes.
SwRI scientists are beginning a program to search for satellites of asteroids using ground-based telescopes and a new optical technology called adaptive optics. This revolutionary technique removes the blurring caused by the Earth's atmosphere and will allow us to see faint satellites close to bright asteroids. The resulting, sharper images can be comparable to those taken with space-based instruments such as the Hubble Space Telescope. Only one satellite has so far been detected, but that required a spacecraft fly-by. Satellites of asteroids hold important clues to the origin and history of the asteroids, and hence to the origin and history of our solar system. We have formed collaborations with the scientists and engineers at state-of-the-art facilities at Mt. Wilson Observatory (near Pasadena CA) and the University of Hawaii's Institute for Astronomy at Mauna Kea Observatory, Hawaii.
Institute scientists are continuing their pioneering work into the nature of oscillations detected in K giant stars. These oscillations, first discovered in the star Arcturus, are thought to be analogous to the 5-minute oscillations seen in the Sun. Evidence of such oscillations in stars other than the Sun has been sought by scientists for over two decades. Using these oscillations, we can perform seismological studies of the interior structure and composition of the stars, similar to studies of the Earth's interior that result from seismic studies of earthquakes. Institute scientists intend to employ an extremely sensitive instrument, initially designed to detect planetary systems around other stars, to measure changes in the observed stellar velocities. The instrument will be operated in collaboration with the University of Arizona and will be located at a dedicated telescope at Kitt Peak National Observatory.
Using state-of-the-art computer simulations, a team of SwRI scientists have been studying the origins and evolution of comets in the outer solar system. Included in their research is: 1) the role of comets in the formation of the outer planets, 2) the delivery of water and organic material to the Earth just after its formation, and 3) the current spatial distribution of comets within the solar system with particular interest on the impact rates with the planets. This team predicted the existence of a previously unsuspected disk of comets surrounding the planetary system - a prediction that has since been confirmed by observations.
SwRI planetary scientists have recently developed a new, extremely fast computer algorithm designed to directly model the formation of the planets for the first time. This code, known as SyMBA, is over ten times faster than any other existing computer algorithm. It will allow SwRI scientists to probe that formation of the Earth and planets with an unprecedented resolution and speed.
Last Updated: 1997 July 23
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