The European Space Agency’s (ESA) BepiColombo spacecraft, which is within the midst of its seven-year journey to Mercury, has successfully accomplished its third flyby of the solar system’s innermost planet.
BepiColombo passed 236 kilometers over the night side of Mercury on Monday, June 19 at 19:34 UTC, and began imaging with its monitoring cameras because it passed into sunlight 13 minutes after its closest approach. The imaging opportunity lasted until 44 hours after closest approach. Beagle Rupes, together with a 218-kilometer diameter peak-ring impact basin that was newly named after Jamaican artist Edna Manley, were notable features in the photographs.
In the course of the flyby, most of BepiColombo’s science instruments were lively. This was the primary flyby where BELA (BepiColombo Laser Altimeter) and MORE (Mercury Orbiter Radio-science Experiment) were lively, though BELA was only on for functional test purposes. BELA will measure the form of Mercury’s surface, while MORE will measure Mercury’s core and gravitational field.
BepiColombo’s lively science instruments collected magnetic, plasma, and particle monitoring data before, during, and after the flyby. This flyby was one other opportunity for the BepiColombo team to envision instrument function and to collect useful science prior to the spacecraft’s orbital mission, which starts in late 2025.
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Image taken during BepiColombo’s third flyby of Mercury, showing surface features. (Credit: ESA)
The 4,100-kilogram spacecraft has made one flyby of Earth, two of Venus, and three of Mercury, with three more flybys of the innermost planet planned before entering Mercury orbit on Dec. 5, 2025.
These flybys are crucial on account of the extreme gravitational field of the Sun. After its launch from Kourou, French Guiana on Ariane 5 mission VA245 in 2018, BepiColombo was traveling at an especially fast speed relative to the Sun.
Nine planetary flybys over seven years can be needed to slow BepiColombo enough, relative to the Sun, to permit the spacecraft to enter orbit around Mercury with its engine and fuel supply. Attempting to enter orbit around Mercury inside a number of months of launch would have required an especially great amount of fuel and thrust.
In reality, the propulsive energy required for a Mercury orbital mission is bigger than that of a mission to fly by Pluto. Just one other spacecraft has orbited Mercury, and that was NASA’s MESSENGER probe, which orbited the planet from 2011 to 2015.
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Infographic showing the timeline for BepiColombo’s journey to orbit Mercury. (Credit: ESA)
Like BepiColombo, MESSENGER used a trajectory utilizing multiple planetary flybys to slow the spacecraft enough, relative to the Sun, to enter orbit around Mercury. MESSENGER conducted one flyby of Earth, two flybys of Venus, and three flybys of Mercury before entering Mercury orbit on March 18, 2011.
The primary probe to Mercury was Mariner 10, which launched on Nov. 3, 1973. Mercury had been completely unexplored before Mariner 10’s first flyby on March 29, 1974. Prior to the spacecraft’s first flyby of Mercury, Mariner 10 flew past Venus on Feb. 5, 1974, and have become the primary spacecraft to make use of an interplanetary gravity assist maneuver to alter its trajectory.
The gravity assist maneuver that Mariner 10 used was developed by Italian scientist Giuseppe “Bepi” Colombo, and it allowed mission planners to make use of an Atlas-Centaur rocket as a substitute of the larger and costlier Titan III. The gravity assist maneuver also allowed the probe to go to Mercury thrice as a substitute of only once.
Gravity assist maneuvers have been a staple of interplanetary missions ever since, and have enabled many missions that may not have been possible without it. BepiColombo’s name honors Mariner 10’s legacy and the scientist who made the mission possible.
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Artist’s impression of Mariner 10 on its option to Mercury. (Credit: NASA)
Besides the gravity assist maneuvers, BepiColombo also needed a state-of-the-art propulsion system to make its mission possible. The spacecraft’s solar electric propulsion system needs to operate for 15,000 hours with the intention to conduct all of the flybys and to get into orbit around Mercury.
The flybys BepiColombo has performed so far have already allowed scientists to publish research in quite a lot of journals. In a conversation with NSF, ESA BepiColombo project scientist Johannes Benkhoff discussed early science returns from the probe.
One example of positive early science returns from BepiColombo involves the solar wind and its interaction with Mercury.
“The coordinated observations with many sensors on each spacecraft monitoring the solar wind interaction with Mercury, passing through boundaries where the solar wind reach the magnetic field etc. has already led so [sic] several publications,” Benkhoff said.
BepiColombo has also made measurements related to Einstein’s Theory of Relativity. Benkhoff mentioned the measurements through the conversation.
“With our radio science instrument MORE we attempt to measure relativistic effects on our signal during solar conjunctions. Measurements are currently being analyzed.”
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ESA infographic of BepiColombo’s science objectives through the Venus flybys. (Credit: ESA)
Scientific measurements were even collected through the spacecraft’s flybys of Venus. As Benkhoff mentioned, “At Venus Moa, Persson et al. confirmed a predicted stagnation region experimentally.” That is referring to a region of Venus’ magnetosheath well above the atmosphere and the way it interacts with the solar wind.
BepiColombo’s remaining flybys of Mercury are scheduled for Sept. 5, 2024, Dec. 2, 2024, and Jan. 9, 2025. The September 2024 flyby will come to inside around 200 kilometers of Mercury’s surface, while the flyby that December will see BepiColombo pass 40,000 kilometers altitude.
The January 2025 flyby will place the spacecraft around 345 kilometers from Mercury’s surface and will probably be the last flyby before Mercury orbital insertion late that 12 months. Before Mercury insertion, two orbiting probes will separate from BepiColombo’s MTM (Mercury Transfer Module). The MTM accommodates the solar electric propulsion system.
The ESA Mercury Planetary Orbiter and the JAXA Mio, also often called the Mercury Magnetospheric Orbiter, will separate from the MTM and explore the innermost planet from orbit in ways in which they might not do with flybys.
The separation of the orbiters will enable the SIMBIO-SYS fundamental mission imager to operate. For the reason that imager is shielded by the spacecraft configuration through the cruise to Mercury, three 1024 x 1024 monochrome monitoring cameras on the MTM are as a substitute used for imagery on all flybys prior to Mercury orbital insertion.
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An illustration showing the monitoring camera angles and the breakdown of the spacecraft’s parts. (Credit: ESA)
The three monitoring cameras are intended for outreach and spacecraft health monitoring, and it shouldn’t be expected that they are going to deliver science returns. The resolution of those camera images on the surface of Mercury isn’t any greater than tens of meters, in line with Benkhoff.
The MESSENGER mission to Mercury mapped all the planet for the primary time and gave scientists a wealth of information and imagery far beyond anything Mariner 10 could have ever done. Amongst MESSENGER’s discoveries were water ice in shadowed craters on the poles and past volcanic activity on Mercury’s surface.
BepiColombo’s mission is to follow up on these discoveries in greater detail. As Benkhoff noted: “MESSENGER has helped us to raised plan our science strategy and identified to recent features not known [sic] when the mission was initiated.”
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Image of a portion of Mercury’s surface taken during BepiColombo’s June 2023 flyby. (Credit: ESA)
Key points of difference between MESSENGER and BepiColombo include having two separate spacecraft in orbit around Mercury as a substitute of 1, many more instruments, and greater instrument coverage and determination by BepiColombo’s Mio and MPO probes. What’s more, Mercury’s southern hemisphere will probably be studied in greater detail as in comparison with MESSENGER, and BepiColombo has a more sensitive radio science capability, using the MORE and Italian Spring Accelerometer instruments, versus MESSENGER.
Instruments just like the MIXS-T high-resolution X-ray imager and the MERTIS thermal IR spectrometer for mineralogy and temperature mapping are also a part of BepiColombo’s science package.
BepiColombo was in a position to reap the benefits of newer technology than was available when MESSENGER launched in 2004, however the expected scientific return of those images hinges on the mission’s protected arrival at Mercury at the top of 2025.