December 1995
December 1995
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On the 7th of December, the Galileo probe entered the Jovian atmosphere, making a 75 minute fiery descent, before all contact was lost with the probe. Initial indications are, that data was relayed successfully from the probe to The Galileo orbiter spacecraft has now started the main phase of its mission, which will see it making multiple passes of both Jupiter and its Moons over the next few years. Its first encounter will be an extremely close fly by of the volcanic moon Io at an altitude of 1000 km. Unfortunately, due to an onboard tape recorder problem, it will not actually image Io during this fly by.
For more details on the Galileo mission, check the Galileo web pages.
It has been reported that 2 Swiss astronomers have tentatively identified a planet orbiting the star 51 Pegasi. The type of planet would probably be a gas giant similar to (and probably a lot larger than) Jupiter. 51 Pegasi is a G4 type star (similar to the Sun) less than 50 light years from our solar system.
The Solar and Heliospheric Observatory (SOHO) was successfully launched in December by an Ariane 4 launcher. More details are available on the SOHO mission in the main article in this Newsletter.
The Hubble Space Telescope has discovered a Brown Dwarf companion to a nearby cool red star called Gliese 229A, 18 light years distant in the constellation Lepus. The Brown Dwarf, is 20-50 times the mass of Jupiter, and is too massive and hot to be a planet, yet too small and cold to be a star. 250,000 times fainter than the Sun, the Brown Dwarf is the faintest object yet observed orbiting another star. Spectroscopic observations of the Brown Dwarf reveal an abundance of Methane, this is characteristic of gas giant planets, not Stars. Stranger planet type bodies have been reported previously, with the discovery of a planet orbiting a pulsar.
Following the successful lunar mission carried out by the Clementine spacecraft in 1993, it seems that the Clementine spacecraft may have discovered lunar ice. Although the chances of the mission discovering lunar ice were dismissed as remote, recent information has been released suggesting that publication of positive results in an American scientific publication is imminent.
The Clementine spacecraft searched for ice using a technique called Bistatic Radar, where radar signals were beamed at oblique angles from Clementine, at the lunar surface, and the bounced signal was detected and measured using based radio telescopes. Much of the resulting data is still being examined, but the possibility of ice on the Moon could be very significant, opening the possibility of future manned missions exploiting this resource for both life support, and for rocket fuels.
The EuroMir 95 mission, in which ESA astronaut, Thomas Reiter is a member along with cosmonauts Gidzenko and Avdeyev, is to be extended beyond its planned 135 day mission by at least 40 days. The reason cited by the Russian space agency is lack of money to launch the relief rocket ! The extended duration of the mission may allow astronaut Reiter to make a second EVA from the MIR space station, following his first EVA in October.
Following in the footsteps of NASA's first three Discovery space missions, a fourth mission has now been selected. The Stardust mission, as it will be know, will capture samples of dust from a comet called Wild-2, and return the samples to Earth in a recoverable capsule. The Stardust spacecraft will be launched in 1999, arriving at the comet in 2004, and returning a sample to the Earth in 2006.
The first three missions to be selected were the Near Earth Asteroid Rendezvous, which will launch in February 1996, and reach the asteroid 433-Eros in 1999. The Mars Pathfinder, which will launch in December 1996, and will land a small lander and a Martian rover on the surface of Mars in July 1997. And the Lunar Prospector mission which was announced as the third mission in February 1995.
SOHO is designed to study the internal structure of the Sun, its extensive outer atmosphere and the origin of the solar wind, the stream of highly ionized gas that blows continuously outward through the Solar System.
The Solar and Heliospheric Observatory (SOHO) is one of ESA and NASA's most ambitious projects for the 1990's. It will help us to understand the interactions between the Sun and the Earth's environment better than has been possible to date. Its legacy may enable scientists to solve some of the most perplexing riddles about the Sun, including the heating of the solar corona, the acceleration of the solar wind, and the physical conditions of the solar interior. It will give solar physicists their first long term, uninterrupted view of the mysterious star that we call the Sun.
That view of the Sun is achieved by operating SOHO from a permanent vantage point 1.5 million kilometers ahead of the Earth in a halo orbit around the L1 Lagrangian point. SOHO Will observe the Sun continuously for at least two years. All previous solar observatories have orbited the Earth, from where their observations were periodically interrupted as our planet `eclipsed' the Sun.
GOLF and VIRGO will perform long and uninterrupted series of oscillations measurements of the full solar disk, respectively in velocity and in the irradiance domain. In this way, information will be obtained about the solar nucleus. SOI/MDI will measure oscillations on the surface of the Sun with high angular resolution. This will permit to obtain precise information about the Sun's convection zone - the outer layer of the solar interior.
SUMER, CDS, EIT, UVCS, and LASCO constitute a combination of telescopes, spectrometers and coronagraphs that will observe the hot atmosphere of the Sun, the corona, extending far above the visible surface. SUMER, CDS and EIT will observe the inner corona. UVCS and LASCO will observe both inner and outer corona. They will obtain measurements of the temperature, density, composition and velocity in the corona, and will follow the evolution of the structures with high resolution.
CELIAS, COSTEP and ERNE will analyze in situ the charge state and isotopic composition of ions in the solar wind, and the charge and isotopic composition of energetic particles generated by the Sun. SWAN will make maps of the hydrogen density in the heliosphere from ten solar diameters. It uses telescopes sensitive to a particular wavelength of hydrogen.
Science investigations designed to image the surface of a comet close up and determine its exact chemical and mineralogical composition have been provisionally selected by NASA and CNES, the French space agency, to be carried out early next century on a comet lander named Champollion.
Slated for launch aboard the International Rosetta Mission, Champollion and a similar comet lander named RoLand, to be provided by a German-led consortium, will be the first spacecraft ever to land on one of these ancient clumps of icy rubble.
Planetary scientists believe that comets were the primary building blocks for the outer planets of the solar system. Cometary bombardment also may have provided a significant fraction of the atmosphere, oceans and organic materials of Earth when it was a young planet.
The overall scientific objective of the Rosetta mission is to produce a global picture of a comet called Wirtanen, including its shape and composition, the nature of the volatiles that it spews out, and the comet surface phenomena that contribute to this process.
The mission is named after the Rosetta Stone, an ancient Egyptian tablet discovered near the town of Rosetta in 1799 that provided a major key to the translation of Egyptian hieroglyphic writing. Jean-Francois Champollion of France, for whom one of the Rosetta mission comet landers is named, played a large part in deciphering it.
"The new knowledge about comets that Rosetta and Champollion promise to return will help us decipher important clues about the earliest stages of the formation of our solar system, just as the Rosetta Stone did with ancient Egyptian hieroglyphics," said Dr. Wesley T. Huntress, Associate Administrator for Space Science, NASA Headquarters, Washington D.C. "The most intriguing potential result from Champollion's investigations is the possible presence of complex organic molecules, which would tell us whether these precursors of life might have been brought to Earth by comets."
Rosetta will be the first spacecraft to orbit a comet. It represents the next major step in cometary science, following several recent reconnaissance flybys of comets by other international spacecraft. Rosetta is the third cornerstone mission in the European Space Agency's long-term space science program called Horizon 2000.
After its scheduled launch aboard an Ariane 5 vehicle in January 2003, the Rosetta spacecraft will perform gravity-assist flybys of Mars and Earth, and then rendezvous with comet Wirtanen in August 2011. It will deploy the Champollion and RoLand surface landers about one year later. Two asteroid flyby encounters also are planned for about halfway through the mission.
The selected Champollion experiments incorporate a number of new technologies, including high-density, three- dimensional electronics, an advanced infrared spectrometer, active pixel imaging sensors with on-chip electronics, an advanced gamma-ray sensor, and a miniaturized, low-power gas chromatograph/mass spectrometer.
A suite of a dozen cameras will provide Earth-bound scientists with their first close-up look at the surface of a comet. One set of cameras, to be provided by Dr. Jean- Pierre Bibring of the Institut d'Astrophysique Spatiale in Orsay, France, will create stereo images of the landscape surrounding the lander. A second camera set supplied by Dr. Roger Yelle of Boston University, Boston, MA, will photograph the surface close to the lander. An even closer look will be generated by a microscope, also supplied by Yelle, which should reveal individual grains in the comet nucleus.
Organic molecules, which may provide clues to the origin of life on Earth, will be identified by a gas chromatograph/mass spectrometer to be contributed by a group led by Dr. Paul Mahaffy of NASA's Goddard Space Flight Center, Greenbelt, MD. Determining the chemical composition of the comet itself is the task of an international consortium headed by Dr. Claude d'Uston of the Centre d'Etude Spatiale des Rayonnements in Toulouse, France. They will use a gamma-ray spectrometer to measure the radiation generated from inside the comet by the cosmic rays that bombard it continuously.
The strength, density and temperature of the comet surface will be measured by probes placed on spikes driven into the surface. These spikes, to be provided by Dr. Thomas Ahrens of the California Institute of Technology, Pasadena, CA, will also serve to anchor the spacecraft firmly to the comet and prevent it from drifting off into space.
The scientific investigators for the provisionally selected instruments are based at 10 U.S. universities, three NASA field centers, three other U.S. laboratories, 10 French institutes, and nine institutes in other countries.
A radio sounding tomographic experiment that would produce a CAT scan-like, three-dimensional image of the comet nucleus is under consideration as an additional Champollion investigation, if financial and technical resources can be made available. It would be provided by Dr. Wlodek Kofman of the Centre d'Etude des Phenomenes Aleatoires et Geophysiques, St. Martin d'Heres, France.
Full confirmation of the Champollion instrument payload is anticipated in about one year, after a formal review and endorsement by the ESA Space Program Committee in February 1996, and verification by NASA and CNES that the selected investigators are able to accommodate changes required to increase instrument collaboration and decrease their costs.
The Champollion project is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for the Solar System Exploration Division of NASA's Office of Space Science, Washington, DC, and the CNES Scientific Program Division, Paris. CNES will contribute several key elements of the mission, including its telecommunication subsystem, batteries, spacecraft separation mechanism, and its ground- based control system.
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