The planetary systems research segment of NASA's space science program centers largely on exploration of our solar system but NASA's latest strategic plan includes "a comprehensive search for planets and planetary formation around other stars." Among the other near term goals are to complete reconnaissance of the solar system; conduct orbital surveys and begin surface exploration of the most fascinating and most accessible bodies; and to complete the inventory of all near-Earth objects measuring one kilometer or more.
An artist's conception of the Galileo probe (center) descending through the atmosphere of Jupiter as the Galileo main spacecraft orbits the planet (upper left). The probe relayed a wealth of data for 57 minutes before it was destroyed by Jupiter's immense gravity.
The long term goals are to go beyond "reconnaissance" of our solar system to detailed surveys, including sample analysis, of the most important bodies, and to identify planets around other stars that might be habitable.
The major planetary systems program in flight status is Galileo, a two-part vehicle consisting of a spacecraft and an instrumented probe designed for a comprehensive examination of Jupiter. Launched in 1990, Galileo arrived at the giant planet in December 1995 and swung into an interim orbit around Jupiter. Among Galileo's early discoveries, its instruments uncovered evidence that Jupiter's moon Io, the most geologically active body in the solar system, has its own magnetic field; if so, it would be the first planetary moon known to have one.
Meanwhile, Galileo's atmospheric probe plunged into the Jovian atmosphere on December 7, 1995 to investigate the planet's composition and physical state. Carrying six instruments, the probe descended by parachute for 57 minutes, reporting a series of "unexpected and often startling" discoveries and relaying its data to the orbiting main spacecraft. The data is undergoing extensive study.
This artist's concept shows the Cassini spacecraft orbiting around Saturn, just after deploying a probe that will descend into the atmosphere of Saturn's moon Titan. To be launched in 1997, Cassini will reach Saturn in July 2004 and orbit the planet for four years thereafter.
On March 14, 1996, Galileo's main engine was fired to boost the spacecraft to a higher orbit and move it further away from the harmful radiations emanating from the giant planet. That put the spacecraft into a final orbit that will enable it to study in detail the planet's four largest moons-Io, Ganymede, Europa and Callisto-and record extensive data about Jupiter itself during 11 orbits over a 23-month span. Galileo is a cooperative U.S./Germany project managed for NASA by Jet Propulsion Laboratory (JPL). The main spacecraft was designed and built by JPL; Ames Research Center has management responsibility for the probe, which was built by Hughes Aircraft.
At Spinoff publication time, NASA was preparing to resume the comprehensive exploration of Mars that began with the Viking orbiters/landers of the late 1970s. Scheduled for launch in November 1996, the Mars Global Surveyor carries five instruments to conduct a systematic mapping of Mars and to obtain extensive data on the geophysical/climatological history of the planet and the evolution of its interior and surface. After reaching Mars in 1997, the spacecraft will conduct its primary mission from polar orbit for two years, then serve as an orbiting communications station for another three years, relaying data from follow-on U.S. and international Mars landers. JPL is program manager; Lockheed Martin Astronautics built the spacecraft.
Under NASA's Discovery program, an effort to develop frequent, small planetary missions that perform high quality scientific investigations at low cost while emphasizing involvement by the academic and research communities, NASA plans to send a Mars lander to the planet in July 1997. Managed by JPL and called Mars Pathfinder, the spacecraft contains a surface rover and three science instruments for acquiring geological/meteorological data and conducting technology experiments to pave the way for future low-cost robotic exploration of Mars.
Other planned Discovery missions include the Lunar Prospector (mid-1997 launch), which will map the Moon's surface composition, magnetic fields and gravity fields from low-altitude orbit; and Stardust (1999), a mission involving rendezvous with a comet and return of an interstellar dust sample. Both spacecraft are built by Lockheed Martin.
The principal planetary mission being readied is Cassini, a joint project of NASA, the European Space Agency (ESA) and the Italian Space Agency, managed for NASA by JPL. The flight vehicle consists of the main Cassini spacecraft and the ESA-built Huygens Probe, a 750-pound, six-instrument package that will descend into the atmosphere of Saturn's moon Titan, which is believed to be chemically similar to the atmosphere of early Earth and is therefore of immense scientific interest.
To be launched in October 1997, Cassini will make flybys of Venus and Jupiter en route to a rendezvous with Saturn in July 2004, where it will be inserted into a loose elliptical orbit. Cassini will release the Huygens Probe during the first orbit, then make approximately 40 revolutions over a span of four years, while the spacecraft's 12 instruments conduct a detailed exploration of the whole Saturnian system, including Titan and the planet's other icy moons.