NASA's Voyager 2 turns 45; here's what it achieved and what's next for the spacecraft

NASA, on August 20, is celebrating the 45th launch anniversary of its Voyager 2 spacecraft which was sent into space back in 1977. The spacecraft, which was designed to last just five years, has stood the test of time and in December 2018 it even became the second spacecraft to enter interstellar space after its twin Voyager 1 (Aug 25, 2012).  As the probe continues to sail through deep space, let us take a brief look at what it accomplished and what happens next.

Voyager 2: Basic fact sheet

Weighing roughly 722 kg, the spacecraft lifted off at 7:59 pm on August 20, 1977, on a Titan III-Centaur rocket from the Cape Canaveral Space Force Station in Florida. The probe contains a suite of 11 instruments which include equipment to photograph a planet and its moons, measure atmospheric properties, analyse a planet’s magnetic field, determine the origin and behaviour of cosmic radiation and study a planet’s surface composition among others. 

Notably, the same instruments are fitted in both the Voyager spacecraft which have made significant contributions to expanding our knowledge about the outer solar system planets. Both Voyager 1 and Voyager 2, previously named Mariner Jupiter and Marine Saturn, are scaled-down versions of NASA's 'Grand Tour' programme which got cancelled in 1971 due to rising costs. 

Interestingly, both these probes took advantage of a rare alignment of the outer solar system planets (Jupiter, Saturn, Uranus and Neptune) which occurs every 175 years, the last of which was in the late 1970s.

Voyager 2 achievements

After its launch in August 1977, the spacecraft crossed the asteroid belt between December 10, 1977, and October 21, 1978. What followed is the first flyby of Jupiter on July 9, 1979, when it captured 17,000 images of Jupiter, its moons, and confirmed Voyager 1’s discovery of a thin ring encircling the planet. It also gathered information about Jupiter’s atmosphere and magnetic field and is accredited with finding the 14th moon of Jupiter. 

(Images of Jupiter and Saturn taken by Voyager 2; Image: NASA)

In the following weeks, the probe used Jupiter's gravity to head toward Saturn and captured 16,000 photographs of the planet, its rings, and many of its known satellites during its flyby in June 1981. After examining Saturn, Voyager 2 again used Saturn's gravity to slingshot toward Uranus and between November 1985 and February 1986, Voyager 2 made its first close-up observations from an altitude of 81,593 km. 

(Uranus and Neptune shown in images by Voyager 2; Image; NASA)

While capturing over 7,000 photographs of the planet, its rings and moons, Voyager 2 discovered two new rings and 11 new Moons of Uranus. The spacecraft's next stop was Neptune, which it observed during its fly-by between June 5 and October 2 of 1989 from an altitude of 5,484 km. Interestingly, Voyager 2's arrival at Neptune made it the first man-made object to fly past Uranus.

During its encounter with Neptune, it captured over 9,000 images of the planet, its atmosphere, dark rings, and moons, discovering six new moons. What's more is that the spacecraft also discovered Neptune's unusual magnetic field, not only tilted 47 degrees from the planet’s axis but also significantly offset from the planet’s centre. After the mission teams were satisfied with the treasure trove of data, they planned to propel the spacecraft beyond the sun's heliosphere and out into interstellar space. 

(Illustration showing the position of the Voyager 1 and 2 spacecraft outside of the heliosphere; Image: NASA)

What's next for Voyager 2?

After decades of relentless exploration, NASA has decided to switch off both the probes as their instruments are facing the wrath of interstellar travel. Over the years, the mission experts have turned off multiple instruments to save power. Both Voyager 1 and Voyager 2 are powered by a system called the radioisotope thermoelectric generators (RTGs), which generates electricity using the heat produced by the decay of plutonium.

Currently, this electricity is being used to power certain instruments such as computers, radio and other systems of the probes, however, the plutonium is expected to last till the 2030s at the most. According to NASA, Voyager 2 is approximately 19.5 billion kilometres away which takes a little under 18 light hours for the Deep Space Network (DSN) to establish contact with it. On the other hand, Voyager 1 is 23.3 billion kilometres from Earth and it takes 20 light hours and 33 minutes for NASA to communicate. 

Estimates also suggest that after NASA loses communication with the probes, they will drift enter the Oort cloud, the sphere of comets around our solar system, in 300 years. Recently, the US space agency reported having faced a glitch in Voyager 1's attitude articulation and control system (AACS) which maintains the spacecraft's orientation.