New Spacecraft to Mercury – First Flyby of the Solar System’s Closest Planet

On 1 October, the European Space Agency and Japan Aerospace Exploration Agency’s bepiColombo mission will make its initial flyby of Mercury to gather images for scientists who anticipate starting its main mission sometime between 2025-2027.

Mercury can teach us a great deal about how rocky, Earth-like planets form. But before we can glean any insights from its surface, we first need to arrive.

Getting to Mercury

Since MESSENGER left its orbit in 2015, scientists have spent considerable time going over its data, planning what comes next and dreaming about landing on Mercury. Although a spacecraft dedicated to studying Mercury won’t launch until 2025, scientists expect it to provide many more answers about this tiny planet so close to our sun.

Spacecraft must gain speed to reach Mercury as its orbit around the Sun is much faster than our own planet’s. Without expelling some of their extra energy, their craft will reach Mercury too fast for gravity to capture and will simply pass them right by without ever touching down.

JPL trajectory specialist Chen-Wan Yen made significant headway toward reaching Mercury orbit through a series of flybys and small propellant maneuvers in the late ’80s, taking an important step toward his longtime dream of getting there.

Flybys

Going directly from Earth to Mercury would require an impractically large amount of fuel and thrust. Therefore, ESA’s bepiColombo spacecraft relies on nine flybys over seven years to gradually slow its speed until entering orbit around its solar system’s innermost planet.

BepiColombo will conduct its third close encounter this week and fly over Mercury’s night side, providing three monitoring cameras with an opportunity to capture black-and-white images of this little-explored planet, according to Johannes Benkhoff, mission project scientist.

BepiColombo will flyby Saturn in “stacked” cruise configuration, with all high-resolution science instruments covered; however, magnetic and plasma experiments should provide valuable data during the hours leading up to and post closest approach.

Preparation

Mariner 10 provided us with our first close look at Mercury, but its unusual magnetosphere warrants further exploration. In response to this need for greater understanding, European Space Agency and Japan’s JAXA have joined forces to construct bepiColombo which will study Mercury from orbit with 11 instruments including Thales Alenia Space’s radio science experiment MORE and spring accelerometer ISA.

BepiColombo will conduct six flybys of Mercury before entering orbit around it in 2025. Each swoop will help bring its craft closer at an increasingly slower speed until its gravity captures it completely.

BepiColombo will also be the first mission to test Einstein’s theory of relativity against Mercury’s orbit, exploring ice in Mercury’s polar craters, as well as discovering why its planet has an atmospheric magnetic field. BepiColombo comprises two orbiters equipped with 11 instruments.

Orbit

Orbits are paths a celestial body or artificial satellite takes around another object due to gravity’s force. Orbits tend to be near circular in shape and closely approximated by Kepler’s laws of planetary motion.

Space vehicles take an undetermined period to complete one orbit, known as their period. The longer an orbit lasts, the closer it gets to its primary body; for instance Mercury completes one short heliocentric orbit every 88 days while all planets in our Solar System, asteroids in the Asteroid Belt, and comets also follow such paths.

An orbit of a space vehicle is defined by its inclination, longitude of ascending node, argument of periapsis and mean anomaly; each element varies with periodicity but not to the degree that precession affects orbits around ecliptic plane.