The Hard Choices To Keep NASA’s Voyager Spacecraft Going

Voyager Golden Record
The Voyager Golden Record

NASA’s oldest explorers are still kicking far beyond the orbit of Pluto. In fact, Voyager 2 is talking to us right now via the large Deep Space Network dish in Canberra, Australia. The distant explorer is beaming data back to Earth at a blistering 159 bytes/sec.

Keeping the pair of explorers going hasn’t been easy, and it won’t get any easier.

The pair of Voyager probes are powered by a trio of radioisotope thermoelectric generators (or RTGs). Heat produced from the natural decay of plutonium-238 is converted into electrical energy that ends up powering the instruments and the heaters that keep them turned on and gathering data.

But each year, the amount of energy produced by these RTGs drops. And with less power (about 40% less than it launched with 40+ years ago), come hard choices.

Recently, the science team and mission managers decided to switch off the heater for the cosmic ray subsystem instrument (CRS) on Voyager 2. CRS made headlines last November when data from it showed Voyager 2 had left the heliosphere (a bubble created by a constant outflow of ionized particles from the Sun).

But the science team did receive some good news. It turns out, the CRS can handle the cold better than expected. The instrument is still returning data even though it dropped to a bone-chilling minus 74 degrees Fahrenheit after the heater was shut off. Testing on Earth more than four decades ago showed it could still operate at minus 49 degrees Fahrenheit.

Voyager Project Manager Suzanne Dodd showered praise on the Voyager pair. “It’s incredible that Voyagers’ instruments have proved so hardy. We’re proud they’ve withstood the test of time. The long lifetimes of the spacecraft mean we’re dealing with scenarios we never thought we’d encounter.”

One of these scenarios in 2017 included switching on thrusters (for both spacecraft) not used in 30+ years. Subtle puffs from these thrusters help keep the spacecraft’s antenna pointed at Earth so it can beam back data.

Hard choices like the ones above will keep happening as part of this new power management plan to keep the spacecraft functioning for as long as possible. More instrument heaters will be switched off in the coming years until the spacecraft ultimately run out of power.

Until then, the Voyager missions will keep exploring the deepest reaches of space. And the data collected will be added to data from NASA’s Interstellar Boundary Explorer (IBEX) as we continue learning more about the heliosphere and interstellar space.

NASA is also gearing up for its next explorer to study the heliosphere. The Interstellar Mapping and Acceleration Probe (IMAP) will build on what the Voyager missions learned about the heliosphere.

IMAP won’t be traveling to the heliosphere boundary. Instead, it will position itself about 1 million miles from Earth towards the Sun at the L1 point (Lagrange point). There, it will look for small bits of cosmic radiation from the rest of the galaxy that makes its way past the protective heliosphere.

IMAP is slated to launch in 2024.

Featured image: Voyager’s Golden Record, Credit: NASA

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