Mercury, located nearer to the Sun than Earth and much smaller, serves as an historical record of early events within our Solar System without being erased by water and ice erosion. Its sun-baked surface has preserved evidence of Earth’s early history without degradation from water and ice erosion.
Chen-Wan Yen of JPL performed meticulous calculations that demonstrated it was possible to use multiple flyby maneuvers (one at Earth and two at Venus) along with small thrusters to put a spacecraft into orbit around Mercury.
How it’s done
Mercury, one of the inner planets, moves fast around its host star; much faster than Earth itself. Therefore, any spacecraft headed toward Mercury needs to slow significantly before being able to capture Mercury’s gravity and enter orbit around it.
Decelerating spacecraft takes considerable energy, which scientists take very seriously. NASA-led MESSENGER mission and European-Japanese bepiColombo missions each take years to reach Mercury.
Both missions employed multiple gravity assists from other planets to save on fuel, beginning with Venus where their spacecraft received a swingby gravity assist and started its trajectory toward Mercury. After further swingbys, their craft will enter Mercury’s orbit and start painting a vivid picture of this strange and ancient planet; scientists hope this data may shed light on how its formation and evolution over 4.5 billion years.
Preparations
As a response to the early rocket successes of the Soviet Union, NASA initiated Project Mercury; which successfully launched seven astronauts into space – five times.
Mercury can be an arduous planet for spacecraft to access; its orbital period is close to that of our Sun and traveling there requires the greatest change in velocity across the Solar System.
As such, MESSENGER must travel an extensive route from its launch site to Mercury’s orbit – taking 7 years with 9 planet flybys and coast arcs on its journey.
The seven Project Mercury astronauts became highly involved in the design of their spacecraft. They insisted upon having windows, as well as helping develop various mission procedures.
Launch
Mercury’s close proximity to the Sun requires spacecraft to exert considerable energy in order to overcome its gravity and enter orbit – an energy drain which cannot be overlooked, even by unmanned craft such as MESSENGER probe (pictured below).
The spacecraft employed an innovative heat shield and one-of-a-kind ceramic fabric sunshade to protect itself from solar winds while still providing optimal thermal performance.
MESSENGER was launched on a seven-year voyage that captured most of Mercury’s visible surface, photographing nearly every part of it and uncovering vast chains of cliffs snaking through its cratered terrain and an intricate network of spider-like troughs in Caloris basin.
BepiColombo, launched on July 15, 2018, by European and Japanese scientists, will use two flyby maneuvers–one each at Earth and Venus–and six Mercury flybys to slow down, enter orbit, and study Mercury’s internal structure, such as its unusually large core. Once in orbit around Mercury, two separate orbiters–Mercury Planetary Orbiter and Mercury Magnetospheric Orbiter–will spend up to one year studying various aspects of its environment including water ice at its poles as well as magnetic field analysiss.
Arrival
Tonight, Messenger spacecraft finally entered Mercury orbit after more than six years of exploration of our solar system and should start sending back images and science data within a day or so.
NASA’s Mariner 10 finished three flybys of Mercury between 1974 and 1975, sparking decades of anticipation among scientists to send another spacecraft there – yet even that mission proved arduous.
Mercury differs from the other outer planets in that its orbit can only be easily entered via solar gravity; Mercury’s surface temperatures make it much harder for it to slow down enough for capture by its own gravitational pull.
BepiColombo was launched by the European Space Agency and Japan Aerospace Exploration Agency on October 20, 2018, marking an ambitious seven-year journey toward Mercury that would utilize 12 flyby maneuvers around Earth, two around Venus and six of Mercury itself to adjust its trajectory and slow its speed.