By Tom Whaley, a solar system ambassador in the outreach program of NASA's Jet Propulsion Laboratory. He lives in Vero Beach.

The American space age began January 31, 1958, with the launch of the first U.S. satellite, Explorer 1, built and controlled by NASA's Jet Propulsion Laboratory (JPL). In the four decades since then, JPL has led the world in exploring all of the solar system's known planets, except Pluto, with robotic spacecraft. The tools developed at JPL for its spacecraft expeditions to other planets have also proved invaluable in providing new insights and discoveries in studies of Earth, its atmosphere, climate, oceans, geology and the biosphere.

JPL's history dates to the 1930s, when legendary Caltech professor Theodore von Kármán oversaw pioneering work in rocket propulsion. Several of his graduate students and assistants tested a primitive rocket engine in 1936 in a dry riverbed area north of the Rose Bowl in Pasadena, California.

Von Karman and his team went on to work on jet-assisted take-off technology for the U.S. Army. It was during this work that the name "Jet Propulsion Laboratory" was born. The group was also to do a technical analysis of the German V-2 rocket program during World War II.

The team of about 100 rocket engineers expanded and began testing of small unguided missiles (named Private) that reached a range of nearly 11 miles. They experimented with radio telemetry from missiles, and began planning for ground radar and radio sets. By 1945, with a staff approaching 300, the group had begun to launch test vehicles from White Sands, New Mexico, to an altitude of 200,000 feet, monitoring performance by radio.

Control of the guided missile was the next step, requiring two-way radio as well as radar and a primitive computer at the ground station. The result was JPL's answer to the German V-2 missile, named Corporal, first launched in May 1947, about two years after the end of war with Germany.

Subsequent Army work further sharpened the technologies of communications and control, of design and test and performance analysis. This made it possible for JPL to develop the flight and ground systems and finally to fly the first successful U.S. space mission, Explorer 1, launched on January 31, 1958.

In late 1958, after Congress created NASA, JPL was transferred from Army jurisdiction to that of the new civilian space agency. It brought to the new agency experience in building and flying spacecraft, an extensive background in solid and liquid rocket propulsion systems, guidance, control, systems integration, and expertise in telecommunications.

In the 1960s, JPL began to conceive and execute robotic spacecraft to explore other worlds. This effort began with the Ranger and Surveyor missions to the Moon, paving the way for NASA's Apollo astronaut lunar landings. During that same period and through the early 1970s, JPL carried out Mariner missions to Mercury, Venus and Mars.

The first search for life on Mars was conducted in 1975 when NASA launched the Viking mission's two orbiter spacecraft and two Martian landers.

Credit for the single mission that has visited the most planets goes to JPL's Voyager project. Launched in 1977, the twin Voyager 1 and Voyager 2 spacecraft flew by the planets Jupiter (1979) and Saturn (1980-81). Voyager 2 then went on to an encounter with the planet Uranus in 1986 and a flyby of Neptune in 1989. Still communicating their findings as they speed out toward interstellar space, the Voyagers are expected to communicate information about the Sun's energy field until perhaps the second decade of the 21st century. In February 1998, Voyager 1 passed NASA's Pioneer 10 to become the most distant human-made object in space.

Other more recent missions include: Magellan to Venus, Galileo to Jupiter, Mars Global Surveyor, Mars Odyssey, Cassini to Saturn, Stardust to Comet Wild-2, Genesis to study the solar wind, and Ulysses to study the Sun's poles.

In the late 1970s, JPL engineers and scientists realized that the sensors they were developing for interplanetary missions could be turned upon Earth itself to better understand our home planet. This has led to a series of highly successful Earth-monitoring missions.