 Artist's depiction of theBepiColombo mission, with the Mercury Planetary Orbiter (left) and Mercury Magnetospheric Orbiter (right) | |
| Mission type | Planetary science |
|---|---|
| Operator | |
| COSPAR ID | 2018-080A |
| SATCATno. | 43653 |
| Mission duration | Cruise: 7 years (planned) 8 years (actual) Science phase: 1 year (planned) 6 years, 5 months and 6 days(in progress) |
| Spacecraft properties | |
| Manufacturer | |
| Launch mass | 4,100 kg (9,000 lb)[1] |
| BOL mass | MPO: 1,230 kg (2,710 lb) Mio: 255 kg (562 lb)[1] |
| Dry mass | 2,700 kg (6,000 lb)[1] |
| Dimensions | MPO: 2.4 m × 2.2 m × 1.7 m (7 ft 10 in × 7 ft 3 in × 5 ft 7 in) Mio: 1.8 m × 1.1 m (5 ft 11 in × 3 ft 7 in)[1] |
| Power | MPO: 150watts Mio: 90 watts |
| Start of mission | |
| Launch date | 20 October 2018, 01:45UTC |
| Rocket | Ariane 5 ECA(VA245)[2] |
| Launch site | Centre Spatial Guyanais,ELA-3[3] |
| Contractor | Arianespace |
| Flyby ofEarth (gravity assist) | |
| Closest approach | 10 April 2020, 04:25 UTC |
| Distance | 12,677 km (7,877 mi) |
| Flyby ofVenus (gravity assist) | |
| Closest approach | 15 October 2020, 03:58 UTC |
| Distance | 10,720 km (6,660 mi) |
| Flyby ofVenus (gravity assist) | |
| Closest approach | 10 August 2021, 13:51 UTC |
| Distance | 552 km (343 mi) |
| Flyby ofMercury (gravity assist) | |
| Closest approach | 1 October 2021, 23:34:41 UTC |
| Distance | 199 km (124 mi) |
| Flyby ofMercury (gravity assist) | |
| Closest approach | 23 June 2022, 09:44 UTC |
| Distance | 200 km (124.3 mi) |
| Flyby ofMercury (gravity assist) | |
| Closest approach | 19 June 2023, 19:34 UTC |
| Distance | 236 km (147 mi) |
| Flyby ofMercury (gravity assist) | |
| Closest approach | 4 September 2024, 21:48 UTC |
| Distance | 165 km (103 mi) |
| Flyby ofMercury (gravity assist) | |
| Closest approach | 1 December 2024, 14:23 UTC |
| Distance | 37,626 km (23,380 mi) |
| Flyby ofMercury (gravity assist) | |
| Closest approach | 8 January 2025, 05:59 UTC |
| Distance | 295 km (183 mi) |
| Mercury orbiter | |
| Spacecraft component | Mercury Planetary Orbiter (MPO) |
| Orbital insertion | November 2026 (planned) |
| Orbital parameters | |
| Perihermion altitude | 480 km (300 mi) |
| Apohermion altitude | 1,500 km (930 mi) |
| Inclination | 90,0° |
| Mercury orbiter | |
| Spacecraft component | Mercury Magnetospheric Orbiter (MMO) |
| Orbital insertion | November 2026 (planned) |
| Orbital parameters | |
| Perihermion altitude | 590 km (370 mi) |
| Apohermion altitude | 11,640 km (7,230 mi) |
| Inclination | 90.0° |
 BepiColombo insignia | |
BepiColombo is a joint mission of theEuropean Space Agency (ESA) and theJapan Aerospace Exploration Agency (JAXA) to the planetMercury.[4] The mission comprises two satellites launched together: theMercury Planetary Orbiter (MPO) andMio (Mercury Magnetospheric Orbiter,MMO).[5] The mission will perform a comprehensive study of Mercury, including characterization of itsmagnetic field,magnetosphere, and both interior and surface structure. It was launched on anAriane 5[2] rocket on 20 October 2018 at 01:45UTC, with an arrival at Mercury planned for November 2026, after a flyby ofEarth, two flybys ofVenus, and six flybys of Mercury.[1][6] The mission was approved in November 2009, after years in proposal and planning as part of the European Space Agency'sHorizon 2000+ programme;[7] it is the last mission of the programme to be launched.[8]
On 15 May 2024, ESA reported that a "glitch" prevented the spacecraft's thrusters from operating at full power during a scheduled manoeuvre on 26 April.[9] On 2 September, 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.[10]
BepiColombo is named afterGiuseppe "Bepi" Colombo (1920–1984), ascientist,mathematician andengineer at theUniversity of Padua,Italy, who first proposed the interplanetarygravity assist manoeuvre used by the 1974Mariner 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 thesolar wind just like a ship traveling through the ocean.[5] In Chinese and Japanese, Mercury is known as the "water star" (水星) according towǔxíng.
Following itsEarth flyby in April 2020,BepiColombo was briefly mistaken for anear-Earth asteroid, receiving theprovisional designation2020 GL2.[11][12][13][14]
The mission involves three components, which will separate into independent spacecraft upon arrival at Mercury.[15]
During the launch and cruise phases, these three components are joined together (with the Magnetospheric Orbiter Sunshield and Interface or MOSIF betweenMio and MPO)[16] to form the Mercury Cruise System (MCS).[17][18]
Theprime contractor forESA isAirbus Defence and Space.[19] 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, which are operated by mission controllers based in Darmstadt, Germany, were successfully launched together on 20 October 2018.[20] The launch took place onAriane flight VA245 from Europe’s Spaceport in Kourou, French Guiana.[21] The spacecraft will have an eight-year interplanetary cruise to Mercury using solar-electric propulsion (ion thrusters) andgravity assists from Earth,Venus and eventual gravity capture atMercury.[1] ESA'sCebreros, Spain 35-metre (115 ft) ground station is planned to be the primary ground facility for communications during all mission phases.
Expected to arrive in Mercury orbit in November 2026, theMio and MPO satellites will separate and observe Mercury in collaboration for one year, with a possible one-year extension.[1] Although originally expected to enter orbit in December 2025, thruster issues discovered in September 2024 before its 4th flyby resulted in a delayed arrival of November 2026.[22] The orbiters are equipped with scientific instruments provided by various European countries and Japan. The mission will characterize the solid and liquid ironcore (3⁄4 of the planet's radius) and determine the size of each.[23] The mission will also completegravitational andmagnetic field mappings. Russia providedgamma ray andneutron spectrometers to verify the existence of water ice in polar craters that are permanently in shadow from the Sun's rays.
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-boundedexosphere"[24] containinghydrogen,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 main objectives of the mission are:[3][25]
The stacked spacecraft will take eight years to position itself to enter Mercury orbit. During this time it will usesolar-electric propulsion and nine gravity assists, flying past the Earth and Moon in April 2020, Venus in 2020 and 2021, and six Mercury flybys between 2021 and 2025.[1]
The stacked spacecraft left Earth with ahyperbolic excess velocity of 3.475 km/s (2.159 mi/s). Initially, the craft was placed in aheliocentric orbit similar to that of Earth. After both the spacecraft and Earth completed one and a half orbits, it returned to Earth to perform agravity-assist maneuver and is deflected towards Venus. Two consecutive Venus flybys reduce the perihelion near to the Sun–Mercury distance with almost no need for thrust. A sequence of six Mercury flybys will lower the relative velocity to 1.76 km/s (1.09 mi/s). After the fourth Mercury flyby, the craft will be in an orbit similar to that of Mercury and will remain in the general vicinity of Mercury (see[1]). Four final thrust arcs reduce the relative velocity to the point where Mercury will "weakly" capture the spacecraft in November 2026 intopolar orbit. Only a small maneuver is needed to bring the craft into an orbit around Mercury with an apocentre of 178,000 kilometres (111,000 mi). The orbiters then separate and will adjust their orbits using chemical thrusters.[28][29]
TheBepiColombo mission proposal was selected byESA in 2000. Arequest for proposals for the science payload was issued in 2004.[30] In 2007,Astrium was selected as the prime contractor, andAriane 5 chosen as thelaunch vehicle.[30] The initial target launch of July 2014 was postponed several times, mostly because of delays on the development of thesolar electric propulsion system.[30] The total cost of the mission was estimated in 2017 as US$2 billion.[31]
As of January 2025[update], the mission schedule is:[32]
| Date | Event | Comment |
|---|---|---|
| 20 October 2018, 01:45 UTC | Launch | |
| 10 April 2020, 04:25 UTC | Earth flyby | 1.5 years after launch |
| 15 October 2020, 03:58 UTC | FirstVenus flyby | According to Johannes Benkhoff ofESA, the probe may possibly be capable of detecting phosphine –the chemical allegedly discovered in the Venusian atmosphere in September 2020 – during this and the following flyby. He stated that "we do not know if our instrument is sensitive enough".[33] On 15 October 2020, the ESA reported the flyby was a success.[34] |
| 10 August 2021, 13:51 UTC | Second Venus flyby | 1.35 Venus years after first Venus flyby. Flyby was a success, and saw BepiColombo come within 552 kilometres (343 mi) of Venus' surface.[35][36] |
| 1 October 2021, 23:34:41 UTC | FirstMercury flyby | Passed 199 kilometres (124 mi) from Mercury's surface.[37] Occurred on what would have been the 101st birthday ofGiuseppe Colombo. |
| 23 June 2022, 09:44 UTC | Second Mercury flyby | 2 orbits (3.00 Mercury years) after 1st Mercury flyby. Closest approach of about 200 kilometres (120 mi) altitude.[38] |
| 19 June 2023, 19:34 UTC | Third Mercury flyby | >3 orbits (4.12 Mercury years) after 2nd Mercury flyby. Closest approach of about 236 kilometres (147 mi) altitude.[39][40] |
| 4 September 2024, 21:48 UTC | Fourth Mercury flyby | ~4 orbits (5.04 Mercury years) after 3rd Mercury flyby. Closest approach of about 165 kilometres (103 mi) altitude.[41] |
| 1 December 2024, 14:23 UTC | Fifth Mercury flyby | 1 orbit (1.00 Mercury year) after 4th Mercury flyby. Closest approach about 37,626 kilometres (23,380 mi) altitude.[42] |
| 8 January 2025, 05:58:52 UTC | Sixth Mercury flyby | ~0.43 orbits (0.43 Mercury years) after 5th Mercury flyby. Closest approach about 295 kilometres (183 mi) altitude.[43][44] |
| November 2026 | Mercury orbit insertion | Spacecraft separation; ~7 Mercury years after 6th Mercury flyby |
| 2027 | MPO in final science orbit | 1.13 Mercury years after orbit insertion? |
| April 2028 | End of nominal mission | 5.82 Mercury years after orbit insertion |
| April 2029 | End of extended mission | 9.98 Mercury years after orbit insertion |
| QinetiQ T6 | Performance[45][46] |
|---|---|
| Type | Kaufman Ion Engine |
| Units on board | 4[47][48] |
| Diameter | 22 cm (8.7 in) |
| Max. thrust | 145 mN each |
| Specific impulse (Isp) | 4300 seconds |
| Propellant | Xenon |
| Total power | 4628W |
The Mercury Transfer Module (MTM) has a mass of 2,615 kg (5,765 lb), including 1,400 kg (3,100 lb) 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 asolar electric propulsion system as the main spacecraft propulsion. Its fourQinetiQ-T6ion thrusters operate singly or in pairs for a maximum combined thrust of 290 mN,[49] 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 14-metre-long (46 ft)solar panels.[50] Depending on the probe's distance to theSun, 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.
Thesolar electric propulsion system has typically very highspecific impulse and lowthrust. This leads to a flight profile with months-long continuous low-thrust braking phases, interrupted by planetarygravity assists, to gradually reduce the velocity of the spacecraft. Moments before Mercury orbit insertion, the MTM will be jettisoned from the spacecraft stack.[50] After separation from the MTM, the MPO will provideMio all necessary power and data resources untilMio is delivered to its mission orbit; separation ofMio from MPO will be accomplished by spin-ejection.
The Mercury Planetary Orbiter (MPO) has a mass of 1,150 kg (2,540 lb) and uses a single-sided solar array capable of providing up to 1000watts and featuring Optical Solar Reflectors to keep its temperature below 200 °C (392 °F). The solar array requires continuous rotation keeping theSun at a low incidence angle in order to generate adequate power while at the same time limiting the temperature.[50]
The MPO will carry a payload of 11 instruments, comprising cameras, spectrometers (IR,UV,X-ray,γ-ray,neutron), a radiometer, a laser altimeter, a magnetometer, particle analysers, a Ka-band transponder, and an accelerometer. The payload components are mounted on the nadir side of the spacecraft to achieve low detector temperatures, apart from the MERTIS and PHEBUS spectrometers located directly at the main radiator to provide a better field of view.[50]
A high-temperature-resistant 1.0 m (3 ft 3 in) diameterhigh-gain antenna is mounted on a short boom on the zenith side of the spacecraft. Communications will be on theX-band andKa-band with an average bit rate of 50kbit/s and a total data volume of 1550Gbit/year. ESA'sCebreros, Spain 35-metre (115 ft) ground station is planned to be the primary ground facility for communications during all mission phases.[50]
The science payload of the Mercury Planetary Orbiter consists of eleven instruments:[51][52]
Mio, or the Mercury Magnetospheric Orbiter (MMO), developed and built mostly byJapan, has the shape of a short octagonal prism, 180 cm (71 in) long from face to face and 90 cm (35 in) high.[3][58] It has a mass of 285 kg (628 lb), including a 45 kg (99 lb) scientific payload consisting of 5 instrument groups, 4 for plasma and dust measuring run by investigators from Japan, and onemagnetometer fromAustria.[3][59][60]
Mio will be spin stabilized at 15rpm with the spin axis perpendicular to the equator of Mercury. It will enter a polar orbit at an altitude of 590 × 11,640 km (370 × 7,230 mi), outside of MPO's orbit.[59] The top and bottom of the octagon act as radiators with louvers for active temperature control. The sides are covered withsolar cells which provide 90 watts. Communications with Earth will be through a 0.8 m (2 ft 7 in) diameterX-band phased arrayhigh-gain antenna and two medium-gain antennas operating in the X-band. Telemetry will return 160Gb/year, about 5kbit/s over the lifetime of the spacecraft, which is expected to be greater than one year. The reaction and control system is based oncold gas thrusters. After its release in Mercury orbit,Mio will be operated bySagamihara Space Operation Center usingUsuda Deep Space Center's 64 m (210 ft) antenna located inNagano, Japan.[51]
_ESA24328694.png)
Mio carries five groups of science instruments with a total mass of 45 kg (99 lb):[3][51]
TheMio 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, asMio is spun up during its separation in 2026, before being ejected from the MPO.[16][17][18]
The Mercury Surface Element (MSE) was cancelled in 2003 due to budgetary constraints.[8] At the time of cancellation, MSE was meant to be a small, 44 kg (97 lb), lander designed to operate for about one week on the surface of Mercury.[28] Shaped as a 0.9 m (2 ft 11 in) diameter disc, it was designed to land at a latitude of 85° near the terminator region. Braking manoeuvres would bring the lander to zero velocity at an altitude of 120 m (390 ft) at which point the propulsion unit would be ejected, airbags inflated, and the module would fall to the surface with a maximum impact velocity of 30 m/s (98 ft/s). Scientific data would be stored onboard and relayed via a cross-dipoleUHF antenna to either the MPO orMio. The MSE would have carried a 7 kg (15 lb) payload consisting of an imaging system (a descent camera and a surface camera), a heat flow and physical properties package, analpha particle X-ray spectrometer, amagnetometer, aseismometer, a soil penetrating device (mole), and a micro-rover.[62]
The data collected for this image, even though it was submitted to theMinor Planet Center as artificial satellite 2018-080A (BepiColombo's official designation), led to it being mistaken for a Near Earth asteroid. The "discovery", announced by the Minor Planet Center as asteroid 2020 GL2, was retracted soon after. This was the third time a spacecraft had been mistakenly announced as a "new asteroid" during an Earth flyby, afterRosetta a.k.a. 2007 VN84 andGaia a.k.a. 2015 HP116. Incidentally, all three of these areESA missions.
This article incorporates text from this source, which is in thepublic domain.The flyby itself was very successful", confirms Elsa. "The only difference to normal cruise phase operations is that near to Venus we have to temporarily close the shutter of any of the star trackers that are expected to be blinded by the planet, similar to closing your eyes to avoid looking at the Sun
Our #BepiColombo @esaoperations team confirm all went well with our #MercuryFlyby last night! Now we wait and see what images & data our instrument teams collected
This article incorporates text from this source, which is in thepublic domain.
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