A tiny speck that is hard to see unless you open your eyes wide. At first glance, it looks like a bit of dust stuck to the photograph. Yet the speck is, remarkably, Earth. The unmanned space probe Voyager 1, launched by the National Aeronautics and Space Administration (NASA), took the picture at the edge of the solar system on February 14, 1990, from a distance of 6 billion㎞ from Earth. The photo is titled ‘Pale Blue Dot’.

In ‘Pale Blue Dot’, Earth is a small body whose presence is hard to notice. From such an Earth, humanity, which claims mastery over all things, is in fact not so grand, as this image shows. Proposed by the eminent astronomer and science popularizer Carl Sagan, ‘Pale Blue Dot’ is regarded as one of the most profound philosophical messages ever distilled by a scientific instrument.

What is interesting is that 34 minutes after taking ‘Pale Blue Dot’, NASA permanently cut power to Voyager 1’s camera. One might think it could have captured even better images, but there was a reason for the decision: to reduce power consumption by instruments as much as possible in order to extend the spacecraft’s overall lifetime.

However, after decades of such stopgap power saving, signs are emerging that the approach is nearing its limits. What is happening to Voyager 1, the veteran probe that in human terms is approaching the ‘age of fifty’?

According to the U.S. scientific community, on the 17th NASA completely halted operation of the Low-Energy Charged Particle (LECP) detector aboard Voyager 1, cutting its power. The LECP measures ions, electrons, and radiation intensity in the space around the spacecraft.

Of the ten scientific instruments aboard Voyager 1 at its 1977 launch, NASA had powered down seven to date. With the LECP now off as well, exactly two instruments remain operational: the plasma instrument and the magnetometer.

Why does NASA keep turning off Voyager 1’s instruments? In most cases the shutoffs were not due to failures but were deliberate, according to plan. Power was cut because Voyager 1’s power generation capability has been gradually weakening.

Voyager 1 carries a radioisotope thermoelectric generator (RTG) that produces electricity from the heat of plutonium. According to NASA, the RTG’s output decreases by about 4 W each year. For this reason, since launch NASA has been turning off instruments one by one in sequence.

Technical aging of a spacecraft is natural. Consequently, space agencies around the world often hold a ‘funeral’ by destroying the vehicle, for example by sending it to plunge into a target body, after the planned mission ends.

Even so, there is a reason NASA is making every effort to extend the life of Voyager 1 in particular. It is because of what the probe represents. Voyager 1 is 25.3 billion㎞ from Earth, a full 170 times the distance between the Sun and Earth. No human-made object is farther away than Voyager 1. Even now, it is acting as the vanguard that leaves humanity’s first trace in the unknown cosmos.

This also means that among spacecraft developed by humanity, Voyager 1 is the first to gather physical characteristics from distant space beyond the solar system. If, due to a lack of power, Voyager 1 were to suffer a blackout, lose all function, and become scrap metal, it would be a major loss for humanity and for science. NASA explained in official materials that “No one wants to turn off the instruments aboard Voyager 1,” and that “However, for now, this is the best measure.”

The problem is that only two instruments are left. This means there is little opportunity remaining to forcibly extend the spacecraft’s life by shutting down more systems. At this rate, the space science community and NASA expect Voyager 1 to reach the end of its life by 2030, even under optimistic assumptions.

Therefore NASA has recently set a separate plan in motion to extend Voyager 1’s life further. It is called the ‘Big Bang Project’. Its core idea is to improve how all onboard systems operate so as to wring out as much power as possible. It is akin to turning off the air conditioner in an electric vehicle to increase driving range.

NASA plans to test ideas devised under the Big Bang Project on both Voyager 1 and its twin, Voyager 2. If the results are good, the same measures will be applied to Voyager 1 as early as July this year. NASA explained, “If spare power is found, it may be possible to restart the LECP.” If the Big Bang Project succeeds, NASA expects the overall lifetime of Voyager 1 to be extended into the early to mid-2030s.