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If Deep Space Hibernation of a probe saves energy and power, then why isn't it implemented on long planetary missions and Interstellar missions like,

New Horizons, Voyagers, Pioneers, Cassini, etc....

Any plan to implement it on future missions ?

(If the voyagers & pioneers had this facility, they could use that saved power to run science instruments, transmitters even now).

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3 Answers 3

up vote 19 down vote accepted

Sometimes you don't want to hibernate the craft, because it has scientific operations to perform during the interplanetary transfer phases. But even when you don't: Deep space hibernation is risky. There is always the risk that the wake-up procedure - whether triggered by the vessel or by the ground station - won't work and the vessel will not recover. It also leaves a long period of time where you have absolutely no way to monitor the state of the vessel and its equipment and have no way to intervene when something goes wrong.

So it should only be done when there is a benefit to it. But often there isn't really a benefit. Temporarily saving energy is often not really an issue. Most vessels are powered by solar cells or radio-isotope generators. Both technologies have some wear over time and lose efficiency, but for neither does it matter how much of their energy is actually used.

The Voyager probes, for example, need to conserve energy not because they used up so much during the first part of their mission but because their radio-isotope generators are reaching the end of their (strictly chronological) lifetime.

For solar-powered crafts, hibernation can make sense for two reasons:

  1. The mission requires the craft to spend long times eclipsed by celestial bodies or leads it on a trajectory far away from the sun, so there are mission phases where solar power is unavailable or severely limited.
  2. Depending on how the craft is constructed, it might be necessary to keep the craft oriented to the sun so the solar panels reach full efficiency. That might require the use of active thrusters which only have a limited amount of propellant. Ignoring orientation and going into power-saving mode during non-critical mission phases can conserve propellant.
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there are one successful wakup procedure by Rosetta Space Craft... –  ReNiSh A R Feb 21 at 10:04
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Rosetta used hibernation for the reason Philip mentions as point 1: Rosetta has solar panels, but its trajectory takes it so far from the sun that the solar panels do not provide enough power to heat and operate the spacecraft. –  Hobbes Feb 21 at 10:42
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A minor thing to add: these probes are built for a specific mission and the specs cover the power necessary to accomplish that mission. The cost difference in making sure a probe can be powered the entire time vs having it sleep during it's journey is relatively minor to the overall cost of the mission itself while bringing a disproportionate amount of risk. –  Chris Lively Feb 21 at 16:12
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Most of the time you don't ever want to use a deep hibernation mode on a spacecraft. If at all possible, you want it active and chatty (with mission control) the entire time, since it means you can do science, monitor its systems, and keep more diagnostic and recovery options available.

The Rosetta probe used deep-sleep mode because for a big part of its journey it was out past Jupiter, and did not receive enough solar power to remain fully functional. It's rendevouz now means it's closer, and can wake up again.

But there is another more interesting reason that has to do with the machine lifetime of the onboard computers: space agencies have models of their computers which basically estimate the number of instruction-operations they can perform before they're likely to experience a hard failure due to wear or uncorrectable errors from radiation bit-flipping.

In the case of very long range spaceprobes, the probability of a failure starts to climb to 1 - that is, leave the ship fully operational and something will go wrong with the onboard computer (which you may or may not be able to recover from) before you reach your target. So deep-sleeping the spacecraft is a way to conserve the computers lifetime - you switch over to very robust real-time clock circuits, and power down the computer entirely.

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Welcome to Space.SE. We like answers that are backed up by references. Do you have any you can add to your answer? –  Hobbes Feb 21 at 14:18
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The probe New Horizons have the hibernation feature implemented, for its long journey to pluto.

After passing Jupiter, New Horizons will spend most of its journey towards Pluto in hibernation mode...

Refer Wiki for more..

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oh.. i just forget to wiki it.... thank you very much... –  ReNiSh A R Feb 21 at 10:05
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