Voyager 1: Its journey to interstellar space

Voyager 1 is a space exploration mission, which was planned and launched by NASA in the 1970s. Its original mission was to perform flybys of Jupiter, Saturn and Titan (a moon of Saturn). Subsequently it has been performing its extended mission of exploring the outer solar system and is currently the only spacecraft in interstellar space. 

Voyager 1 also carries with it the Golden Record, which contains 115 images and sound recordings of music, languages and natural phenomenon. The Golden Record was put in the spacecraft in the hope that an extraterrestrial civilisation may one day discover it and learn about Earth and human civilisation.

On 5 September, 1977, Voyager 1 was launched from the Kennedy Space Flight Center. It flew by Jupiter on 5 March, 1979, Saturn on 12 November, 1980 and then began its mission to the outer solar system. It entered interstellar space on 25 August, 2012. The probe is still operational and is expected to remain functional until approximately 2025 when its power source will be unable to provide enough electricity to its scientific instruments.

Voyager 1 performed several critical orbital maneuvers to gain enough energy to reach interstellar space.  A Hohmann Transfer was needed for the spacecraft to reach Jupiter from Earth.  A Hohmann transfer is the most energy efficient manner for a spacecraft to move between two orbits. In this case, Voyager was first placed into Earth orbit after launch, then it activated it's thrusters to increase its kinetic energy, allowing it move to into an elliptical orbit that coincided with the position of Jupiter at the time when the spacecraft would be at the furthest point of the ellipse.  For a successful execution of this maneuver, Voyager 1 had to engage its thrusters during a specific launch window, to allow the spacecraft to intercept Jupiter accurately, while also minimizing journey time.

After reaching Jupiter, Voyager 1 flew behind the planet and performed a gravitational slingshot maneuver. As the craft approached Jupiter, the gravitational pull from the planet helped it gain speed and as the probe flew past the planet in a hyperbolic trajectory, its exit speed was greater than its approach speed. The slingshot maneuver actually allowed the spacecraft to "steal" some energy and angular momentum from Jupiter's orbit. The probe repeated the gravitational slingshot maneuver at Saturn and the cumulative increase in velocity allowed Voyager 1 to gain enough energy to escape the solar system within a few decades.

Picture: Collected

Theoretically a Hohmann transfer may have been performed from Earth orbit, with the apogee point located outside the solar system,  which would have allowed Voyager to travel directly into interstellar space without any planetary flybys. However, that would have taken much more time than the two gravity assist maneuvers, since the probe would only have had as much energy and velocity as it could gain by burning fuel. In subsequent years, there have been proposals to use planetary gravitation assisted maneuvers as a form of an 'Interplanetary Expressway'.

Voyager 1 accomplished all its mission objectives successfully and is still providing new scientific data. It has photographed Jupiter, Saturn and a number of its moons of both planets.                                                                

It made many new discoveries, including the first observation of Jupiter's rings. The probe has taken many significant photographs, including the first photo of the Earth and Moon in orbit together, and a photo of the entire solar system including all the Sun, eight planets and Pluto. Although the probe's lifespan is almost at its end, it has provided decades worth of scientific data and will hopefully pave the way for new missions that go out even further into the stars.