BepiColombo is a joint mission of the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) to the planet Mercury. The mission comprises two satellites launched together: the Mercury Planetary Orbiter (MPO) and Mio (Mercury Magnetospheric Orbiter, MMO). The mission will perform a comprehensive study of Mercury, including characterization of its magnetic field, magnetosphere, and both interior and surface structure. It was launched on an Ariane 5 The total cost of the mission was estimated in 2017 as US$2 billion.
Names
BepiColombo is named after Giuseppe "Bepi" Colombo (1920–1984), a scientist, mathematician and engineer at the University of Padua, Italy, who first proposed the interplanetary gravity assist manoeuvre used by the 1974 Mariner 10 mission, a technique now used frequently by planetary probes.
Mio, the name of the Mercury Magnetospheric Orbiter, was selected from thousands of suggestions by the Japanese public. In Japanese, Mio means a waterway, and according to JAXA, it symbolizes the research and development milestones reached thus far, and wishes for safe travel ahead. JAXA said the spacecraft will travel through the solar wind just like a ship traveling through the ocean.
- Study the origin and evolution of a planet close to its parent star
- Study Mercury's form, interior, structure, geology, composition and craters
- Investigate Mercury's exosphere, composition and dynamics, including generation and escape
- Study Mercury's magnetised envelope (magnetosphere) – structure and dynamics
- Investigate the origin of Mercury's magnetic field
- Test Einstein's theory of general relativity by measuring the parameters gamma and beta of the parameterized post-Newtonian formalism with high accuracy.
Mercury is too small and hot for its gravity to retain any significant atmosphere over long periods of time, but it has a "tenuous surface-bounded exosphere" containing hydrogen, helium, oxygen, sodium, calcium, potassium and other trace elements. Its exosphere is not stable as atoms are continuously lost and replenished from a variety of sources. The mission will study the exosphere composition and dynamics, including generation and escape.
The orbiters are equipped with scientific instruments provided by various European countries and Japan. The mission will characterize the solid and liquid iron core ( of the planet's radius) and determine the size of each. The mission will also complete gravitational and magnetic field mappings. Russia provided gamma ray and neutron spectrometers to verify the existence of water ice in polar craters that are permanently in shadow from the Sun's rays.
Mission overview
The mission involves three components, which will separate into independent spacecraft upon arrival at Mercury.
- Mercury Transfer Module (MTM) for propulsion, built by ESA.
- Mercury Planetary Orbiter (MPO) built by ESA.
- Mercury Magnetospheric Orbiter (MMO) or Mio built by JAXA.
During the launch and cruise phases, these three components are joined (with the Magnetospheric Orbiter Sunshield and Interface or MOSIF between Mio and MPO)
ESA is responsible for the overall mission, the design, development assembly and test of the propulsion and MPO modules, and the launch. The two orbiters are operated by mission controllers based in Darmstadt, Germany. The spacecraft operations manager of BepiColombo was Elsa Montagnon until 2021, and is now Ignacio Clerigo. ESA's Cebreros, Spain ground station is the primary ground facility for communications during all mission phases.
Mission timeline
thumb|upright=1.0|right|BepiColombo, imaged at [[Northolt Branch Observatories, 16 hours after the Earth flyby. The bright satellite passing by is INSAT-2D.]]thumb|Mercury on 23 June 2022 during the 2nd gravity assist at the planet
Before launch
The BepiColombo mission proposal was selected by ESA in 2000. A request for proposals for the science payload was issued in 2004. In 2007, Astrium (now Airbus Defence and Space) was selected as the prime contractor, and Ariane 5 chosen as the launch vehicle. The initial target launch of July 2014 was postponed several times, mostly because of delays on the development of the solar electric propulsion system.
Gravity assist maneuvers
thumb|Mercury on 5 September 2024 during the 4th gravity assist at the planetThe stacked spacecraft left Earth with a hyperbolic excess velocity of . Initially, the craft was placed in a heliocentric orbit similar to that of Earth. After both the spacecraft and Earth completed one and a half orbits, it returned to Earth to perform a gravity-assist maneuver and was deflected towards Venus.
Following its Earth flyby in April 2020, BepiColombo was briefly mistaken for a near-Earth asteroid, receiving the provisional designation .
Two consecutive Venus flybys reduced the perihelion near to the Sun–Mercury distance with almost no need for thrust. A sequence of six Mercury flybys lowered the relative velocity to . After the fourth Mercury flyby in 2024, the spacecraft is in an orbit similar to that of Mercury and remains in the general vicinity of the planet.
Science during Venus flybys
After the potential biomarker phosphine has been tentatively discovered in the Venusian atmosphere in September 2020, ESA scientists suggested that BepiColombo might be able to detect the compound during its two Venus flybys in 2020 and 2021. However, it was not clear if the spacecraft's instruments were sufficiently sensitive and there has been no announcement of such detection since.
During the first Venus flyby in October 2020, seven science instruments and a radiation monitor onboard the Mercury Planetary Orbiter, and three instruments onboard Mio, were active and gathering data. The observations were coordinated with JAXA's Akatsuki, the only active spacecraft orbiting Venus at that time, as well as Earth-based observatories.
Science during Mercury flybys
During the first Mercury flyby in October 2021, the spacecraft captured its first images of the target planet using the M-CAM monitoring cameras on the Mercury Transfer Module. Some of the scientific instruments on both orbiters were also active during the flyby, exploring the magnetic and particle environment around Mercury and measuring the planet's gravity.
During the second flyby in June 2022, the M-CAM cameras imaged, among other targets, the crater Heaney with a candidate volcano, an important target for the spacecraft's primary mission. This crater has been recently named after Seamus Heaney following a request from the M-CAM team. Some of the scientific instruments have been again active, measuring the magnetic, plasma, and particle environment around the spacecraft.
During the third flyby in June 2023, the MPPE suite of instruments on Mio was used to map the magnetosphere of Mercury. Based on these data, scientists described various expected features of the magnetosphere, but also made new discoveries: 1) a low latitude layer containing particles with much broader energy range than ever observed on Mercury, 2) energetic hydrogen ions trapped at low latitude and near the equator, and 3) cold plasma ions of oxygen and sodium, as well as signatures of potassium, which were probably ejected from the planet's surface by micrometeorites or the solar wind. Mio<nowiki/>'s observations during this flyby also identified the chirping-like discrete whistler-mode emission waves previously observed in Earth's magnetosphere but so far unknown from Mercury.
In May 2024, computers on BepiColombo (as well as on another ESA mission, Mars Express) reported a sharp increase in the number of memory errors, coinciding with a massive solar flare from the active region AR3664, at that time facing away from Earth. The event was also observed in detail by ESA's Solar Orbiter.
During the fourth flyby in September 2024, the spacecraft had, for the first time, a clear view of Mercury's south pole. The M-CAM 2 and 3 cameras provided images of the polar region, as well as the Vivaldi crater and a crater newly named Stoddart after Margaret Olrog Stoddart following a request from the M-CAM team.
During the fifth flyby in December 2024, using the MERTIS instrument, BepiColombo became the first spacecraft ever to observe Mercury in mid-infrared light. During the sixth and final Mercury flyby in January 2025, the M-CAM 1 camera imaged the permanently shadowed craters Prokofiev, Kandinsky, Tolkien, and Gordimer near the planet's north pole.
Thruster issues
On 15 May 2024, ESA reported an issue preventing the spacecraft's thrusters from operating at full power during a scheduled manoeuvre on 26 April 2024. On 2 September 2024, ESA reported that to compensate for the reduced available thrust, a revised trajectory had been developed that would add 11 months to the cruise, delaying the expected arrival date from 5 December 2025 to November 2026.
Future
Four final thrust arcs will reduce the relative velocity to the point where Mercury will "weakly" capture the spacecraft in November 2026 into polar orbit. Only a small maneuver is needed to bring the craft into an orbit around Mercury with an apocentre of . The orbiters then separate and will adjust their orbits using chemical thrusters.
{| class="wikitable"
! Date
! Event
! Comment
|- bgcolor=#ccffcc
| 20 October 2018, 01:45 UTC
| Launch
|
|- bgcolor=#ccffcc
| 10 April 2020,<br/>04:25 UTC
| Earth flyby
| 1.5 years after launch
|- bgcolor=#ccffcc
| 15 October 2020, 03:58 UTC
| First Venus flyby
| On 15 October 2020, the ESA reported the flyby was a success. Closest approach at a distance of about 10 720 km from the planet's surface.
|- bgcolor=#ccffcc
| 10 August 2021,<br/>13:51 UTC
| Second Venus flyby
| 1.35 Venus years after first Venus flyby. Flyby was a success, and saw BepiColombo come within of Venus's surface.
|- bgcolor=#ccffcc
| 1 October 2021,<br/>23:34:41 UTC
| First Mercury flyby
| Passed from Mercury's surface. Occurred on the 101st anniversary of Giuseppe Colombo’s birth.
|- bgcolor=#ccffcc
| 23 June 2022,<br/>09:44 UTC
| Second Mercury flyby
| ~2 orbits (3 Mercury years) after 1st Mercury flyby. Closest approach of about altitude.
|- bgcolor=#ccffcc
| 19 June 2023,<br/>19:34 UTC
| Third Mercury flyby
| ~3 orbits (4.1 Mercury years) after 2nd Mercury flyby. Closest approach of about altitude.
|- bgcolor=#ccffcc
| , 21:48 UTC
| Fourth Mercury flyby
| ~4 orbits (5.0 Mercury years) after 3rd Mercury flyby. Closest approach of about altitude.
|- bgcolor=#ccffcc
| 1 December 2024, 14:23 UTC
| Fifth Mercury flyby
| 1 orbit (1.0 Mercury year) after 4th Mercury flyby. Closest approach about altitude.
|- bgcolor=#ccffcc
| 8 January 2025, 05:58:52 UTC
| Sixth Mercury flyby
| ~0.4 orbits (0.4 Mercury years) after 5th Mercury flyby. Closest approach about altitude.
|-
| November 2026
| Mercury orbit insertion
| 7.8 Mercury years after 6th Mercury flyby. 60-hour orbital period
|-
| December 2026
| , detaches from MPO
| 9.3-hour orbital period
|-
| Early 2027
|
| 2.36-hour orbital period
|-
| April 2028
| End of nominal mission
|
|-
| April 2029
| End of planned extended mission
|
|}
thumb|Timeline of BepiColombo from 20 October 2018 to 2 November 2025. Red circle indicates flybys.|left|850x850px<gallery mode=packed heights=180>
File:Animation of BepiColombo trajectory.gif|Animation of BepiColombo trajectory from 20 October 2018 to 2 November 2025<br/><br/>For more detailed animation, see this video
File:Animation of BepiColombo trajectory around Mercury.gif|Animation of BepiColombos trajectory around Mercury
File:MMO&MPO-Orbits.svg|Planned orbits for Mio and MPO, the two probes of the BepiColombo mission
</gallery>
Mission components
Mercury Transfer Module
{| class="wikitable floatright"
|-
! QinetiQ T6 !! Performance
|-
| Type || Kaufman Ion Engine
|-
| Units on board || 4
|-
| Diameter ||
|-
| Max. thrust || 145 mN each
|-
| Specific impulse<br/>(I<sub>sp</sub>) || 4300 seconds
|-
| Propellant || Xenon
|-
| Total power || 4628 W
|}
The Mercury Transfer Module (MTM) has a mass of , including of xenon propellant, and is located at the base of the stack. Its role is to carry the two science orbiters to Mercury and to support them during the cruise.
The MTM is equipped with a solar electric propulsion system as the main spacecraft propulsion. Its four QinetiQ-T6 ion thrusters operate singly or in pairs for a maximum combined thrust of 290 mN, making it the most powerful ion engine array ever operated in space. The MTM supplies electrical power for the two hibernating orbiters as well as for its solar electric propulsion system thanks to two solar panels. Depending on the probe's distance to the Sun, the generated power will range between 7 and 14 kW, each T6 requiring between 2.5 and 4.5 kW according to the desired thrust level.
The solar electric propulsion system has typically very high specific impulse and low thrust. This leads to a flight profile with months-long continuous low-thrust braking phases, interrupted by planetary gravity assists, to gradually reduce the velocity of the spacecraft. Moments before Mercury orbit insertion, the MTM will be jettisoned from the spacecraft stack. After separation from the MTM, the MPO will provide Mio all necessary power and data resources until Mio is delivered to its mission orbit. Separation of Mio from MPO will be accomplished by spin-ejection.
<gallery mode="packed" heights="100">
File:Mercury Transfer Module in space simulator ESA387743.jpg|MTM in space simulator
File:BepiColombo Mercury Transfer Module solar wing deployment.jpg|MTM solar wing deployment
File:BepiColombo MTM ESTEC.jpg|MTM at ESTEC
File:Mercury Transfer Module thruster detail(1).jpg|MTM thruster detail
</gallery>
Mercury Planetary Orbiter
The Mercury Planetary Orbiter (MPO) has a mass of and uses a single-sided solar array capable of providing up to 1000 watts and featuring Optical Solar Reflectors to keep its temperature below . The solar array requires continuous rotation keeping the Sun at a low incidence angle in order to generate adequate power while at the same time limiting the temperature.
- BepiColombo Laser Altimeter (BELA), developed by DLR in cooperation with the University of Bern, the Max Planck Institute for Solar System Research (MPS) and the Instituto de Astrofísica de Andalucía.
- Italian Spring Accelerometer (ISA), developed by Italy
- Mercury Magnetometer (MPO-MAG, MERMAG), developed by Germany and United Kingdom
- Mercury Orbiter Radio-science Experiment (MORE), developed by Italy and the United States
- Probing of Hermean Exosphere by Ultraviolet Spectroscopy (PHEBUS), developed by France and Russia
- Search for Exosphere Refilling and Emitted Neutral Abundances (SERENA), made up of 2 neutral and 2 ionised particle analysers:
- ELENA (Emitted Low-Energy Neutral Atoms) developed by Italy;
- STROFIO (STart from a ROtating Field mass spectrOmeter) developed by United States;
- MIPA (Miniature Ion Precipitation Analyser) developed by Sweden;
- PICAM (Planetary Ion CAMera) developed by the Space Research Institute (Institut für Weltraumforschung, IWF), Russian Space Research Institute (IKI), Institut de recherche en sciences de l'environnement (CETP/IPSL), European Space Research and Technology Centre (ESTEC), Research Institute for Particle and Nuclear Physics (KFKI-RMKI) and the Max Planck Institute for Solar System Research (MPS). It has a mass of , including a scientific payload consisting of 5 instrument groups, 4 for plasma and dust measuring run by investigators from Japan, and one magnetometer from Austria.
Mio will be spin stabilized at 15 rpm with the spin axis perpendicular to the equator of Mercury. It will enter a polar orbit at an altitude of , outside of MPO's orbit.
<gallery mode=packed heights=150>
File:BepiColombo MMO ESTEC.jpg|Mio at ESTEC before stacking
File:BepiColombo MMO'mio' Supended.jpg|Mio being lifted from the container by a crane
File:Mercury Magnetospheric Orbiter on top of Mercury Planetary Orbiter.jpg|Mio on top of MPO (without sunshield)
</gallery>
Science payload of Mio
Mio carries five groups of science instruments with a total mass of :
- High-Energy Particle instrument for electrons (HEP-ele)
- High-Energy Particle instrument for Ions (HEP-ion)
- Energetic Neutrals Analyzer (ENA)
- Mercury Magnetometer (MMO-MGF), studies Mercury's magnetic field, magnetosphere, and interplanetary solar wind
- Plasma Wave Investigation (PWI), studies the electric field, electromagnetic waves, and radio waves from the magnetosphere and solar wind
- Mercury Sodium Atmosphere Spectral Imager (MSASI), studies the thin sodium atmosphere of Mercury
- Mercury Dust Monitor (MDM), studies dust from the planet and interplanetary space
Magnetospheric Orbiter Sunshield and Interface
thumb|upright=0.8|Full stack with sunshield on top
The Mio orbiter requires additional thermal control on the cruise to Mercury, in addition to umbilicals to the MPO. The European Space Agency thus provided the Magnetospheric Orbiter Sunshield and Interface (MOSIF), a white shroud that is shaped like a conical frustrum to provide clearance, as Mio is spun up during its separation in 2026, before being ejected from the MPO.
Mercury Surface Element (cancelled)
The Mercury Surface Element (MSE) was cancelled in 2003 due to budgetary constraints. At the time of cancellation, MSE was meant to be a small, , lander designed to operate for about one week on the surface of Mercury.
See also
- List of European Space Agency programmes and missions
- Exploration of Mercury
- MESSENGER – the first spacecraft to orbit Mercury
References
External links
- BepiColombo website by the European Space Agency
- BepiColombo Operations website by the European Space Agency
- BepiColombo website by JAXA
- BepiColombo website by JAXA's Institute of Space and Astronautical Science
- BepiColombo website by NASA's Solar System Exploration
- BepiColombo website by the National Space Science Data Center
- The BepiColombo mission to Mercury, edited by Johannes Benkhoff, Go Murakami and Ayako Matsuoka. Space Science Reviews. 216–217 (2020–2021)
- BepiColombo article on eoPortal by ESA