This artifact is a Development Test Model (DTM) for the Voyager spacecraft that consists of facsimile and dummy parts manufactured by the Jet Propulsion Laboratory. It was acquired by NASM in 1977 and placed on display in the Exploring the Planets gallery shortly thereafter. In 1987, JPL removed the DTM bus for use in developing the Magellan Venus spacecraft, which was similar in design, and replaced it with a facsimile.

The Voyager program was conceived in the mid-1960's as a mission to explore the outer planets using Mariner-style spacecraft. Officially, the original objective to investigate all of the outer planets in a "grand tour" was scaled back to Jupiter and Saturn exclusively due to budgetary cut-backs. However, Voyager 2 was launched on August 20, 1977 and placed on a slow flight path to Jupiter. Subsequently, Voyager 1 was launched on September 5, 1977 and arrived at Jupiter first in March 1979 and Saturn in November 1980. Because Saturn's moon, Titan, is the only other planet with a predominately nitrogen atmosphere, Voyager 1's trajectory was designed to pass within 2550 miles. This manuever caused the flight path to leave the ecliptic plane and out of the Solar System. Voyager 2 encounter Jupiter in July 1979 and Saturn in August 1981. Its slower flight path was designed to allow it to go on to Uranus in January 1986 and then to Neptune in August 1989 as the funding became available to continue the mission.

The Voyager TV cameras, ultraviolet and infrared spectrometers, and photopolarimeter are mounted on a scan platform that is stabilized about two axes of rotation. These instruments can be pointed with and accuracy of better than one-tenth of a degree. Because the spacecraft travel at speeds in excess of 35,000 mph, and the light levels at Neptune can be 900 times fainter than those on Earth, the spacecraft angular rates were programmed to extremely small to prevent smearing.

"Voyager was the little spacecraft that could."-Edward Stone, Voyager Chief Scientist, Jet Propulsion Laboratory

Voyager

In the 1970s, NASA's leadership conceived their most daring planetary science expedition, Voyager. It took advantage of a rare astronomical event. Once every 176 years, the giant planets on the outer reaches of the solar system all gather on one side of the sun, and such a configuration was due to occur in the late 1970s. This geometric lineup made possible in a single flight close-up observation of all the planets in the outer solar system (with the exception of Pluto), the "Grand Tour." This planetary alignment offered a crucial advantage: As the spacecraft passed each planet, gravity would bend its flight path and increase its velocity enough to deliver it to the next destination. Known as "gravity assist," this complex process gave the spacecraft a "slingshot" boost at each planet. Neptune, the outermost planet in the mission, thus could be reached in 12 rather than 30 years.

In 1964 NASA conceived Pioneer 10 and 11, the first probes to explore the solar system beyond Mars, and these became the precursors of the Grand Tour of Voyager. Severe budgetary constraints hampered the projects, delaying their launch until 1972 and 1973, respectively Pioneer 10 and 11 yielded invaluable science, Designed to last for 30 months, they performed for more than 20 years, returning useful data on Jupiter and Saturn, as well as providing our first look beyond the solar system at interstellar space.

Voyager stood as a greater challenge. A four-planet "grand tour" was theoretically possible. But design was crucial. A single spacecraft might accomplish the mission, but would have to be extraordinarily complex and expensive to travel to the outer reaches of the solar system, endure for more than a decade, and reliably operate a range of scientific instruments. To simplify the mission and limit the expense, the mission relied on two Voyager spacecraft to conduct intensive flyby studies only of Jupiter and Saturn-in effect repeating on a more elaborate scale the flights of the two Pioneers. With an $865 million budget, engineers designed the two Voyagers to conduct as much science and to last as long as possible. Launched from the Kennedy Space Center, Voyager 2 lifted off on August 20, 1977 and Voyager 1 on September 5, 1977, each taking different trajectories to the outer planets.

By December 1980, the two Voyager spacecraft had accomplished successfully their objectives at Jupiter and Saturn. Flybys of the two outermost giant planets, Uranus and Neptune, proved possible-and irresistible-to mission scientists. As the two spacecraft flew across the solar system, scientists re-programmed them via radio communications to aim for the outer planets. Eventually Voyager 1 and Voyager 2 explored all the giant outer planets, including their unique systems of rings and magnetic fields, as well as 48 of their moons.

The two spacecraft returned information to Earth that revolutionized planetary science, helping resolve some key questions while raising intriguing new ones about the origin and evolution of the solar system. For example, although astronomers had studied Jupiter through telescopes on Earth for centuries, scientists were surprised by many of the Voyager findings. It revealed that the Great Red Spot was a complex storm moving in a counterclockwise direction. Easily the greatest unexpected discovery at Jupiter, scientists also found active volcanism on the satellite Io, the first time active volcanoes had been seen on another body in the solar system. Together, the two Voyagers observed the eruption of nine volcanoes on Io, and there is evidence that other eruptions occurred between the Voyager encounters. It discovered that plumes from the volcanoes extend to more than 190 miles above the surface. Io's volcanoes result from heating through tidal pumping between Jupiter and other moons.

The two Voyagers took well over 100,000 images of the outer planets, rings, and satellites, as well as millions of magnetic, chemical spectra, and radiation measurements. They discovered rings around Jupiter, shepherding satellites in Saturn's rings, new moons around Uranus and Neptune, and geysers on Triton. The last imaging sequence was Voyager 1's portrait of most of the solar system, showing Earth and six other planets as sparks in a dark sky lit by a single bright star, the Sun. In the first decade of the twenty-first century Voyager 1 continued to provide important scientific data about the heliopause, the outer limits of the Sun's magnetic field and outward flow of the solar wind.

This artifact is a Development Test Model (DTM) that consists of facsimile and dummy parts manufactured by the Jet Propulsion Laboratory. It was acquired by the National Air and Space Museum in 1977 and placed on display in the Exploring the Planets gallery shortly thereafter. In 1987, JPL removed the DTM bus for use in developing the Magellan Venus spacecraft, which was similar in design, and replaced it was a facsimile.