Voyager: Going, Going, Not Yet Gone
Saturday, February 2nd, 2013
NASA’s twin over-achieving Voyager probes are going steady, still sending scientific information back to Earth after all these years.
by AJ Plunkett
Have you ever been out driving in the winter and realized you don’t have that much gas left, and you’re still miles from where you need to be? To conserve fuel, you switch off the heater. You’re fine in your winter wear. For a while. Then you get a chill. Then your feet are cold, then unbearably frozen. Back on goes the heater.
Just for a little while, you say. You’ll turn it off again, so you can get a little farther along on your journey.
Well, Voyager is still out there — way out there — getting colder.
For years, NASA handlers have been turning off instruments, one by one, to conserve energy aboard the seemingly unstoppable space probe and its twin, Voyager 2.
Launched in 1977 on a mission to study Jupiter and Saturn — and with a life expectancy of five years — the space probes accomplished their duties and were ordered to fly on to Uranus and Neptune. NASA ultimately reprogrammed the probes to head toward deep outer space to see what they could find.
More than 35 years after their initial launch, the probes are now in the outer edges of our solar system, about to break into interstellar space, and they’re still sending scientists new information about the universe.
All that from the 470 watts of 30-volt DC power that the three plutonium-powered radioisotope thermoelectric generators on the spacecraft began generating upon launch. Three decades later, as the plutonium continues to decay, the spacecraft are losing 4.2 watts a year and the generators could flicker out by 2020.
Powering Down, Piece by Piece
Over the years, several heaters, pieces of backup equipment, various cameras and optics, and science instruments have been shut down.
The cameras on Voyager 1 were some of the first elements to go, and were switched off shortly after the mission to study Saturn.
And just like a traveler on a lonely road, NASA briefly turned the cameras on in 1990 just long enough for Voyager to take a look back toward home and snap what is famously known as a “family portrait” of our solar system’s planets.
Voyager also took a shot of the “Pale Blue Dot” showing through a milky circular sheath of stars.
Starting in 1990, NASA handlers set a schedule for turning off instruments. In 2011, NASA controllers ordered Voyager 1 to shut an IRIS replacement heater that had been left on to warm the scan platform for an ultraviolet spectrometer, or UVS, which can spot certain elements and compounds by detecting the light they emit.
It’s cold in space, and the temperature has dipped well below what the UVS was designed to function in, according to NASA. But a year later, the UVS — the last platform instrument still powered up on either probe — remained operational and providing useful data.
In the cold, feet freezing, still moving along.
This year, NASA’s end-of-mission operations plan calls for shutting down UVS operations all together, finally powering off the unit as well as its own heater and a scan platform supplemental heater.
One of the last pieces of equipment scheduled to be shut off will be the digital tape recorder, which has been gathering the information from all the other instruments and playing them back to Earth every day via a Deep Space Network of antennas.
For 35 years.
Scheduled to take place about two-thirds of the way into 2014, NASA officials say that the power reduction may be delayed, depending on whether the communication network is still operating well enough. It also depends on whether the output from the plutonium-fueled generators is “better than predicted.”
Because, you know, Voyager has a habit of surprising us.
AJ Plunkett is a freelance writer in Virginia with experience in covering defense and aerospace industries, as well as health care issues. AJ blogs via Contently.com