Engineers adjust Voyagers 1 & 2 because of steadily dropping power


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In recognition that the available power on both Voyager 1 and Voyager 2 continues to drop due to the age of the spacecraft, engineers have decided to make some major changes in how they operate both spacecraft.

For example, to save power on Voyager 2 they have turned off the heaters for the instrument that confirmed last year that the spacecraft had entered interstellar space. Even so, the instrument is still functioning and sending back data. It is expected it will continue to work for some time before finally succumbing to the cold of deep space.

They have also decided to reactivate the back-up thrusters on Voyager 2, just as they did with Voyager 1 in 2017.

Another challenge that engineers have faced is managing the degradation of some of the spacecraft thrusters, which fire in tiny pulses, or puffs, to subtly rotate the spacecraft. This became an issue in 2017, when mission controllers noticed that a set of thrusters on Voyager 1 needed to give off more puffs to keep the spacecraft’s antenna pointed at Earth. To make sure the spacecraft could continue to maintain proper orientation, the team fired up another set of thrusters on Voyager 1 that hadn’t been used in 37 years.

Voyager 2’s current thrusters have started to degrade, too. Mission managers have decided to make the same thruster switch on that probe this month. Voyager 2 last used these thrusters (known as trajectory correction maneuver thrusters) during its encounter with Neptune in 1989.

It is thirty years since those thusters on Voyager 2’s were used. If they work it will be an incredible testament to the engineers who designed both spacecraft.

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6 comments

  • wayne

    Q:
    (excuse, I did not follow the link)
    –How many watts are being generated for each probe, right now?

  • TL

    From the article:
    “Each of the probes is powered by three radioisotope thermoelectric generators, or RTGs, which produce heat via the natural decay of plutonium-238 radioisotopes and convert that heat into electrical power. Because the heat energy of the plutonium in the RTGs declines and their internal efficiency decreases over time, each spacecraft is producing about 4 fewer watts of electrical power each year. That means the generators produce about 40% less than what they did at launch nearly 42 years ago, limiting the number of systems that can run on the spacecraft.”

  • TL

    From the JPL site:
    “Electrical power is supplied by three Radioisotope Thermoelectric Generators (RTGs). The current power levels are about 249 watts for each spacecraft.”
    https://voyager.jpl.nasa.gov/mission/spacecraft/

    My math got me 252 watts (down from 420 watts when new) from info in the first article. Pretty amazing power budget considering the lightbulbs on the front of my house (pre-LED) used 450 watts.

  • wayne

    TL-
    Thank you!

  • Jay

    TL,
    Good job with your numbers. Sorry this is a late post, I am catching up on the posts.

    When I saw this post, I did some numbers but they came up higher, but I did not take in to account that the 312 SiGe unicouples in the MHW generators are breaking down over time.

    One good book I used on research on the RTGs and the third Voyager spacecraft that was a test article was “Space Nuclear Radioisotope Systems” by David Buden. Good reference material, diagrams, and equations.

  • wayne

    Jay–
    good stuff, thank you.

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