It was 1977. A gallon of gas cost 65 cents. The disco craze was on. And Star Wars premiered in theatres, enthralling millions with its curious characters rocketing around with the forces of good and evil in a fictional galaxy.
A real space adventure would launch from Cape Canaveral, Fla., that year — NASA’s Voyager spacecraft. Today, the unmanned probes Voyager 1 and Voyager 2 are speeding farther into the cosmos than any other object created by humankind. Soon, Voyager is expected to exit our solar system.
Norman Ness, professor emeritus in UD’s Department of Physics and Astronomy, is a principal investigator on the Voyager mission. He designed the magnetometers aboard the spacecraft, which measure magnetic fields from planets and moons. For three and a half decades, he faithfully has been analyzing the data the rockets transmit back to Earth.
Ness, now 79, flew to NASA’s Jet Propulsion Laboratory in Pasadena, Calif., this past September to celebrate the mission’s 35th anniversary.
Referring to Voyager as “the 20th century’s robotic spacecraft,” Ness explains that the goal was to get the rockets out to the “Big Four” planets of Jupiter, Saturn, Uranus and Neptune. Voyager was so successful—for example, discovering volcanoes on Io, one of Jupiter’s moons, and making new revelations about Saturn’s rings—that NASA decided to extend the mission.
Thanks to a technique called “successive encounter trajectory with gravity assist,” Ness says, Voyager was flung into the heavens like a pebble from a slingshot, and the twin spacecraft have just kept on going.
In December 2004, at 94 astronomical units (8.7 billion miles from the sun), Voyager 1 crossed the “termination shock,” where the solar wind slows down abruptly from 1.5 million miles per hour as the spacecraft encountered the interstellar wind.
Voyager then entered a turbulent region called the heliosheath. Next up is the heliopause, where solar and interstellar wind are in equilibrium. Once Voyager passes through this boundary, the spacecraft will leave the sun’s domain and enter interstellar space.
The 1970s technology zooms along at about a million miles per day, Ness says. Power is supplied by Radio Isotope Thermoelectric Generators (RITGs), which use Plutonium 238. This radioactive element has a half life of about 88 years, or a range of 69–99 years, enough to keep Voyager flying at least another 35 years, if not more, according to Ness.
With the limited hearing ability of current antennas on Earth, Ness says the team will only be able to listen to Voyager until 2025. In 2020, they will begin turning off the instruments, one by one. Voyager is expected to cross into the interstellar medium long before then, possibly within the next year or two.
“It’s been a hell of a good ride,” Ness says.