Voyager researcher marks new milestone

Norman Ness, a professor at the Bartol Research Institute at UD, with a scale model of Voyager 1

3:15 p.m., May 24, 2005--As NASA’s Voyager 1 spacecraft sails through the solar system’s final frontier--a vast, turbulent expanse where the sun’s influence ends and solar wind crashes into the thin gas between stars--a scientist with the University of Delaware’s Bartol Research Institute is looking on with pride and wonder.

Norman F. Ness, a UD professor who joined the Bartol Research Institute in 1987 after a long and distinguished career at NASA’s Goddard Space Flight Center, is one of two principal investigators who have remained with the Voyager project since its inception in 1971 and launch six years later. The other is Stamatios Krimigis of the Applied Physics Laboratory.

Ness, who will retire in June, took great delight in an official announcement by NASA during a meeting of Earth and space science organizations on Tuesday, May 24, in New Orleans that Voyager 1 is now 8.7 billion miles from the sun and has become the first human-built spacecraft in history to enter the heliosheath, the region of space beyond the termination shock zone that marks the beginning of the end of solar influence.

The termination shock is where the solar wind, a thin stream of electrically charged gas blowing outward from the sun, is suddenly slowed by pressure from gas between the stars. At the termination shock, the solar wind slows dramatically from its average speed of between 700,000 and 1.5 million miles per hour and becomes denser and hotter.

When the speed of the solar wind suddenly decreases, the embedded solar magnetic field simultaneously suddenly increases, Ness said. There are also characteristic increases in the fluctuations of the magnetic field on either side of the termination shock.

On the Voyager 1 spacecraft, the instrument to measure the solar wind stopped working long ago so it was left to the sensitive dual magnetometers built 30 years ago at the Goddard Space Flight Center to reveal the existence of the termination shock. The measured magnetic field was observed to have suddenly increased by two-to-four times the average magnitude in the heliosphere, persuasively proving the crossing of the termination shock and entrance into the heliosheath, Ness said.

“I am going out with an exquisite result,” Ness said of his pending retirement and the scientific coup for Voyager 1. “The termination shock region is a plasma boundary we have been seeking for a very long time. It is like a Holy Grail of astrophysics. Estimating where it would be was a great challenge because there were no previous observations of such a phenomenon, and we had only theory to guide us. Finally, Voyager 1 has crossed it.”

The finding is of great importance, as is the expedition that led to it. “Voyager is one of the premiere scientific missions NASA has ever undertaken,” Ness said.

Voyager spacecraft graphic courtesy of NASA

“The Voyagers were launched in 1977, when there was a unique celestial array of the four great outer planets, Jupiter, Saturn, Uranus and Neptune,” Ness said, “an array that permitted the spacecraft a very short trip time from Earth to the outermost planets by use of the technique known as gravity assist.”

He likened gravity assist to a slingshot, with the Voyagers launched on a trajectory that made use of the planets’ gravitational fields to transfer energy to the spacecraft, thus speeding them on their way.

“The situation where we have the four target planets in position for a spacecraft to be sequentially boosted in speed only occurs once every 175 years,” Ness said, adding that it took the spacecraft 12 years to reach Neptune with the gravity assist and would have taken twice that long without.

Although the mission was originally planned as one to Jupiter and Saturn, Ness said mission designers early on took into account the special understanding that “the Grand Tour mission might be realized.”

“The continuation of scientific studies on Voyager 1 and Voyager 2 after the primary encounters were supported by Congress and achieved remarkable new results at those faraway planets,” Ness said. “We have seen spectacular successes at each encounter.”

Eventually, the mission was extended, framed as the Voyager Interstellar Mission, resulting in the trip through the termination shock region.

“Power on Voyager 1 could last until 2020, so this spacecraft could become humanity’s first mission to interstellar space,” according to Eric Christian, discipline scientist for the Sun-Solar System Connection research program at NASA headquarters in Washington, D.C.

Voyager mission graphic courtesy of NASA

The Voyager spacecraft were both equipped with radioisotope thermoelectric generators to produce electrical power for their systems and instruments. The generators, provided by the U.S. Department of Energy, produce electricity from the heat generated by the natural decay of plutonium dioxide and are still in working order nearly three decades after launch.

The spacecraft are controlled and their data returned through NASA’s Deep Space Network, a global spacecraft tracking system operated by the Jet Propulsion Laboratory, which was in charge of managing the entire spacecraft project.

“The operation of Voyager is a living monument to the dedication of many technicians and scientific personnel organized by NASA and supported by Congress,” Ness said. “Voyager is surely a most unique laboratory bench and it is hoped these new observations and discoveries will encourage Congress to continue support of what can really be called a most pioneering adventure of mankind into the cosmos.”

Ness, who holds a doctorate from the Massachusetts Institute of Technology, was a research scientist and administrator at NASA’s Goddard Space Flight Center from 1960-86. He succeeded Martin A. Pomerantz as the director of the Bartol Research Institute in 1987.

In 1991, the Bartol Research Institute became the lead institution in the NASA-funded Delaware Space Grant Consortium with Ness as director.

For more information about Voyager’s interstellar mission, visit [http://voyager.jpl.nasa.gov/].

Article by Neil Thomas
Photo by Duane Perry

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