After 8 Years in Space, BepiColombo Is Finally Approaching Mercury
Overview
Following a difficult journey, the probe will soon begin unravelling the mysteries of Mercury's magnetic field and internal structure. Launched in October 2018 as a joint mission between the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA), BepiColombo has spent nearly eight years threading a complex path through the inner solar system before it can finally settle into orbit around the smallest and least-explored rocky planet. Visit robosino.com
A Journey Shaped by Gravity Assists
Reaching Mercury is deceptively hard: the planet's proximity to the Sun means spacecraft are constantly accelerated by solar gravity, making it easier to overshoot than to slow down and enter orbit. Rather than relying on a massive fuel load, BepiColombo uses a combination of solar-electric ion propulsion and a series of planetary flybys — one at Earth, two at Venus, and six at Mercury itself — to gradually shed velocity. Each flyby bends the trajectory and trims speed a little more, a technique pioneered conceptually by Italian mathematician Giuseppe "Bepi" Colombo, after whom the mission is named.
Two Orbiters, One Shared Ride
BepiColombo is actually two spacecraft traveling together, attached to a Mercury Transfer Module that provides propulsion and power during cruise. The Mercury Planetary Orbiter (MPO), built by ESA, will study the planet's surface, composition, and exosphere. The Mercury Magnetospheric Orbiter, known as Mio and built by JAXA, is dedicated to analyzing Mercury's unusual magnetic field and its interaction with the solar wind. Once in Mercury orbit, the two modules will separate and operate independently.
What BepiColombo Aims to Answer
Mercury is the only rocky planet besides Earth with a global magnetic field, but its origin remains poorly understood. Scientists also want to know why Mercury has such an oversized iron core relative to its size, what shaped its heavily cratered and unusually dark surface, and how ice could persist in permanently shadowed polar craters despite the planet's extreme daytime heat. BepiColombo's instruments will also test predictions of Einstein's general relativity by precisely tracking Mercury's orbit, building on data gathered by NASA's earlier Mariner 10 (1974–75) and MESSENGER (2011–2015) missions.
A Bumpy Final Stretch
The mission's final approach hasn't been trouble-free. A thruster anomaly reduced available propulsion during a critical phase, forcing mission planners to push back the orbit-insertion timeline. That delay is part of why, roughly eight years after launch, BepiColombo is only now closing in on its destination rather than having already begun full science operations.
FAQ
Q: Why does it take so long to reach a planet so close to Earth?
A: The Sun's gravity accelerates spacecraft as they head inward, so reaching Mercury requires shedding far more energy than reaching outer planets — hence the many gravity-assist flybys.
Q: How long will BepiColombo study Mercury?
A: The mission is designed for roughly one year of nominal science operations once both orbiters are in place, with the possibility of an extended mission depending on spacecraft health.
Source
Originally published at www.wired.com.