Voyager 2

Voyager 2 is a highly advanced space probe launched by NASA on August 20, 1977.

It was designed to explore the outer reaches of our Solar System. This mission was part of the larger Voyager program. The spacecraft was built to study gas giants and ice giants. Voyager 2 is unique because it is the only spacecraft to visit Uranus and Neptune. It is now traveling through the interstellar medium, which is the space between stars.

To navigate the vastness of space, Voyager 2 uses a complex Attitude and Articulation Control Subsystem (AACS). This system includes gyroscopes and celestial referencing instruments. It uses a Sun sensor and a Canopus star tracker to maintain its position. These tools help the probe keep its high-gain antenna pointed toward Earth. The spacecraft also uses 16 hydrazine thrusters for attitude control. These thrusters help with stabilization and trajectory correction maneuvers. A single titanium tank holds the hydrazine fuel needed for these tasks.

Powering a machine so far from the Sun requires a special method. Voyager 2 uses three radioisotope thermoelectric generators, known as MHW RTGs.

Each RTG contains 24 pressed spheres of plutonium oxide. These spheres produce heat, which the generators convert into electricity. At launch, the three RTGs provided a total of 470 watts of power. This power level halves every 87.7 years. Scientists use this energy to run various scientific instruments. In 2023, NASA began using a backup power reservoir to keep instruments running.

The mission began with a plan called the "Grand Tour." Scientists noticed a rare alignment of the outer planets in the late 1970s. This alignment allowed a probe to visit multiple planets using gravity assists. A gravity assist uses the gravitational pull of a planet to change a spacecraft's path. NASA originally planned two groups of probes for this massive project. One group would visit Jupiter, Saturn, and Pluto. The other group would visit Jupiter, Uranus, and Neptune. Eventually, the project was scaled back and renamed the Voyager program.

Voyager 2 completed its primary mission by visiting four different planetary systems. It encountered the Jovian system, which includes Jupiter, in July 1979. It then reached the Saturnian system in August 1981.

Following this, it visited the Uranian system in January 1986. Its final planetary encounter was with the Neptunian system in August 1989. During these flybys, the probe passed many moons. For example, it flew by Ganymede at 62,130 km during its Jupiter encounter. It also passed Neptune very closely, at only 4,950 km from the planet's center.

The spacecraft carries 11 different scientific instruments to study space. These include cameras with narrow-angle and wide-angle lenses.

The cameras use various filters to see different wavelengths of light. These filters include ultraviolet, violet, blue, green, orange, and clear spectrums. Other instruments, like the Magnetometer (MAG), investigate magnetic fields. The Plasma Science (PLS) instrument measures the properties of plasma ions. The Cosmic Ray Subsystem (CRS) helps determine the origin of cosmic rays. These tools allow the probe to send back detailed data about the universe.

Communication with Voyager 2 is a massive technical feat. The probe uses a large parabolic high-gain antenna to send data. This data travels via the S-band and X-band radio frequencies. Earth receives these signals using the NASA Deep Space Network. One important communication site is the DSS 43 antenna near Canberra, Australia. As the probe moves further away, the data rate decreases due to the inverse-square law. At the distance of Jupiter, the rate can be as high as 115.2 kilobits per second. If communication is impossible, a Digital Tape Recorder can store 64 megabytes of data.

Today, Voyager 2 is in its extended mission phase. It officially entered the interstellar medium on November 5, 2018.

This means it has left the Sun's heliosphere. It is now providing the first direct measurements of interstellar plasma density and temperature. The probe continues to travel through the interstellar medium while remaining inside the Solar System. It follows in the footsteps of Voyager 1, which entered interstellar space in 2012. Voyager 2 remains a vital link to the world beyond our Sun.