A new map of the magnetosphere of Mercury

Map of Mercury's magnetosphere
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Using data obtained during the June 2023 fly-by by the European-Japanese probe BepiColombo, scientists have now published a new detailed map of the magnetic field that surrounds Mercury.

That map is to the right. From the caption:

A textured sphere representing Mercury is shown with magnetic field lines compressed on the sunward side and streaming out into a tail on the nightside. The BepiColombo spacecraft’s trajectory is drawn passing through the magnetosphere from dawn to dusk, close to the planet’s surface. Various features in the magnetosphere are depicted and labelled with text. Following the order in which they were detected by the spacecraft, this includes the bow shock, magnetopause, low-latitude boundary layer, cold ion cloud, plasma sheet horn and ring current.

You can read the peer-reviewed paper here [pdf]. Note that this research does not include data obtained during BepiColumbo’s fourth fly-by of Mercury in September. Furthermore, the spacecraft will do two more fly-bys before arriving in orbit in 2026, where it will then separate into two separate orbiters in complementary orbits. Thus, this magnetic map of Mercury is merely a rough draft, and will be significantly refined by the end of the mission.

ESA releases images taken by BepiColombo during Mercury fly-by

Mercury as seen by BepiColombo September 4, 2024
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The European Space Agency (ESA) yesterday released images taken by the BepiColombo probe as it completed its fourth fly-by of Mercury on its long journey to enter orbit around that planet.

The picture to the right, cropped, reduced, and sharpened to post here, was taken four minutes after the closest approach of about 103 miles.

Four minutes after closest approach, a large ‘peak ring basin’ came into BepiColombo’s view. These mysterious craters – created by powerful asteroid or comet impacts and measuring about 130–330 km across – are called peak rings basins after the inner ring of peaks on an otherwise flattish floor.

This large crater is Vivaldi, after the famous Italian composer Antonio Vivaldi (1678–1741). It measures 210 km across, and because BepiColombo saw it so close to the sunrise line, its landscape is beautifully emphasised by shadow. There is a visible gap in the ring of peaks, where more recent lava flows have entered and flooded the crater.

BepiColombo still has two more fly-bys of Mercury to do before entering orbit in November 2026. At that time the spacecraft’s two orbiters, one from Europe and the other from Japan, will separate and take up complementary orbits.

Due to thruster problem, the Mercury orbiter BepiColombo will arrive at Mercury almost one year late

The joint ESA and JAXA Mercury mission BepiColombo will now reach its destination eleven months late because its ion electric thrusters are producing less thrust than expected.

The spacecraft is actually made up of two orbiters, one built by the European Space Agency (ESA) and the second built by Japan’s space agency JAXA. During launch and the journey to Mercury each is attached to a third spacecraft called the Mercury Transfer Module (MTM), which has the large electric ion thrusters used for making the mid-course corrections prior to and after each fly-by of the Earth (once), Venus (twice), and Mercury (six) before finally entering orbit around Mercury. It has already completed the Earth, Venus and three Mercury fly-bys.

In April 2024 engineers discovered that during a mid-course correction on April 26st the MTM’s thrusters failed to produce the desired thrust.

Engineers identified unexpected electric currents between MTM’s solar array and the unit responsible for extracting power and distributing it to the rest of the spacecraft. Onboard data imply that this is resulting in less power available for electric propulsion. ESA’s BepiColombo Mission Manager, Santa Martinez explains: “Following months of investigations, we have concluded that MTM’s electric thrusters will remain operating below the minimum thrust required for an insertion into orbit around Mercury in December 2025.”

In order not to lose the mission entirely, the science team has come up with a new trajectory that will have it fly past Mercury on its fourth fly-by on September 4, 2024 only 103 miles above the surface, 22 miles closer than originally planned. This will give it a larger slingshot speed boost to help make up for the under-powered thrusters. It will then make its planned fifth and sixth Mercury fly-bys in December ’24 and January ’25, the adjusted route having it arrive in Mercury orbit eleven months later than planned, in November 2026.

This new plan however means that the pictures taken this week during the Mercury fly-by will provide some nice high resolution details, far better than those produced by the earlier fly-bys.

Potentially serious problem on BepiColombo Mercury mission

According to the European Space Agency (ESA), engineers have discovered what could be a potentially serious problem on BepiColombo mission that is presently on its way to Mercury.

The solar arrays and electric propulsion system on the Mercury Transfer Module are used to generate thrust during the spacecraft’s complex journey from Earth to Mercury.

However, on 26 April, as BepiColombo was scheduled to begin its next manoeuvre, the Transfer Module failed to deliver enough electrical power to the spacecraft’s thrusters.

A combined team from ESA and the mission’s industrial partners set to work the moment the issue was identified. By 7 May, they had restored BepiColombo’s thrust to approximately 90% of its previous level. However, the Transfer Module’s available power is still lower than it should be, and so full thrust cannot yet be restored.

The press release implies that this issue won’t prevent the spacecraft from entering orbit around Mercury as scheduled in December 2025, but one wonders how that could be if it doesn’t have sufficient power to do the proper course correction during its last major flyby of Mercury in September 2024. If it misses its precise route in ’24 it could miss Mercury entirely in ’25.

Engineers are analyzing the situation to see what can be done to get it to Mercury, while also trying to figure out what caused this power problem in the first place in order to fix it.

BepiColumbo completes third Mercury flyby

Mercury as seen by BepiColumbo
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On June 19, 2023, the European Mercury orbiter BepiColumbo made the third of six planned flybys of Mercury on its way to orbit around that planet in 2025.

The closest approach was only 146 miles above the planet’s surface. Though no pictures were taken at that point because it was Mercury’s night side, as the spacecraft moved away it used one of its monitoring cameras, designed primarily to monitor the spacecraft itself, to look back at the planet. The picture to the right, cropped, reduced, and sharpened to post here, is one of the first taken. From its caption:

The image was taken at 19:49 UTC (21:49 CEST) by the Mercury Transfer Module’s monitoring camera 3, when the spacecraft was about 2536 km from the planet’s surface. Closest approach took place at 19:34 UT (21:34 CEST) on the night side of the planet at about 236 km altitude. The back of the Mercury Planetary Orbiter’s high-gain antenna and part of the spacecraft’s body is also visible in front of Mercury in this image.

Despite the dark nature of the image, several interesting geological features are seen in beautiful detail. Of particular interest is Beagle Rupes, a 600 km-long scarp that snakes over the surface. In this view it is seen cutting through a distinctive elongated crater named Sveinsdóttir, which likely got its shape from an impactor striking the surface at an angle.

The next flyby will occur on September 5, 2024.

BeppiColombo’s first images of Mercury

Mercury by BebiColomo
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This past weekend the European/Japanese duel-orbiter mission made its first flyby of Mercury, taking its first images of that planet.

The photo to the right is one example, cropped and reduced slightly to post here. It was taken by the spacecraft’s monitoring cameras, designed for engineering purposes, which means the resolution is not very high and the camera is positioned so that parts of the spacecraft were visible in each shot. For example, the white strut in the lower right is the spacecraft’s magnetometer boom, which also was used to gather data during the flyby.

Still, the photos demonstrated that the spacecraft is pointing correctly and on course. It will complete five more Mercury fly-bys before going into orbit in 2025.

The next flyby will occur in June ’22.

BepiColombo about to make first of six Mercury flybys

The European/Japanese BepiColombo probe will make its first of six fly-bys of Mercury on October 1, 2021, as it steadily adjusts its flight path to enter orbit around the planet in 2025.

The mission is made up of two Mercury orbiters, Europe’s Mercury Planetary Orbiter and Japan’s Mio orbiter.

During the flybys it is not possible to take high-resolution imagery with the main science camera because it is shielded by the transfer module while the spacecraft is in cruise configuration. However, two of BepiColombo’s three monitoring cameras (MCAMs) will be taking photos from about five minutes after the time of close approach and up to four hours later. Because BepiColombo is arriving on the planet’s nightside, conditions are not ideal to take images directly at the closest approach, thus the closest image will be captured from a distance of about 1000 km.

The first image to be downlinked will be from about 30 minutes after closest approach, and is expected to be available for public release at around 08:00 CEST on Saturday morning. The close approach and subsequent images will be downlinked one by one during Saturday morning.

The cameras provide black-and-white snapshots in 1024 x 1024 pixel resolution, and are positioned on the Mercury Transfer Module such that they also capture the spacecraft’s solar arrays and antennas. As the spacecraft changes its orientation during the flyby, Mercury will be seen passing behind the spacecraft structural elements.

These will be the first close-up pictures of Mercury since the Messenger orbiter mission ended in 2015.

Two flybys of Venus set by two spacecraft on August 9th and 10th

Two European planetary probes, one launched to study the inner solar enviroment and the second to study Mercury, are going to fly past Venus only 33 hours apart on August 9th and 10th.

Solar Orbiter, a partnership between ESA and NASA, will fly by Venus on 9 August with a closest approach of 7995 km at 04:42 UTC. Throughout its mission it makes repeated gravity assist flybys of Venus to get closer to the Sun, and to change its orbital inclination, boosting it out of the ecliptic plane, to get the best – and first – views of the Sun’s poles.

BepiColombo, a partnership between ESA and JAXA, will fly by Venus at 13:48 UTC on 10 August at an altitude of just 550 km. BepiColombo is on its way to the mysterious innermost planet of the solar system, Mercury. It needs flybys of Earth, Venus and Mercury itself, together with the spacecraft’s solar electric propulsion system, to help steer into Mercury orbit against the immense gravitational pull of the Sun.

The two spacecraft will zip past a different side of Venus. For a variety of reasons, the imagery gathered will not of high resolution, though both spacecraft will gather data that will eventually be correlated with similar data being gathered by Japan’s Akatsuki probe, in orbit around Venus since 2015.

Mercury probe BepiColombo probe flies past Venus

Venus during BepiColombo fly-by
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The two-pronged European and Japanese probe BepiColombo today has completed its first of two fly-bys of Venus on its way to an arrival at Mercury in 2025.

The image to the right is one of 64 taken during the fly-by. The science team has created a movie from those images, showing Venus slide past as the spacecraft slewed to view it. During the fly-by the instruments on board its Japanese and European orbiters, both of which will separate and operate independently once they reach Mercury, gathered data of Earth’s sister planet.

The spacecraft still needs one more Venus fly-by plus six past Mercury to get it on a trajectory that will put it in orbit around Mercury. It has also already completed one fly-by past Earth in this complicated route.

BepiColombo begins first operational engine burn

The European/Japanese mission to Mercury has begun the first operational firing of its four ion engines, set to last for the next two months.

This might seem like a ridiculously long burn, since most conventional rocket engines fire for minutes, not months. These are ion engines, however, far more efficient but producing a very tiny acceleration. It takes a long time for their burns to accumulate a velocity change.

BepiColombo tests its ion engines

The joint European/Japanese mission BepiColombo has begun testing its ion engine thrusters for the first time in space as it heads to Mercury.

Testing took place during a unique window, in which BepiColombo remained in continuous view of ground-based antennas and communications between the spacecraft and those controlling it could be constantly maintained. This was the only chance to check in detail the functioning of this fundamental part of the spacecraft, as when routine firing begins in mid-December, the position of the spacecraft will mean its antennas will not be pointing at Earth, making it less visible to operators at mission control.

They have so far successfully tested two of the four engines.

ESA unveils dual orbiter mission to Mercury

After twenty years of development, the European Space Agency this week finally unveiled the completed dual orbiters that it hopes to launch on a seven year journey to Mercury in October 2018.

The 4,100-kilogram BepiColombo consists of two orbiters that will launch together — the ESA-managed Mercury Planetary Orbiter (MPO) and the JAXA-owned Mercury Magnetospheric Orbiter (MMO). The two spacecraft will be delivered to the orbit around Mercury stacked on top of each other by the Mercury Transfer Module (MTM). During the seven-year journey, the MMO will be shielded from the sun by the MMO Sunshield and Interface Structure (MOSIF), which will also serve as a mechanical and electrical interface between the two orbiters.

“MPO focuses on the planet, the surface and the interior size,” said Reininghous. “The orbit is a polar one — 480km times approximately 1500km — a little bit elliptical but extremely close to the planet as such with a return period of 2.3 hours. The data return is estimated at 1.5 gigabit per year.”

The MMO will focus on the planetary environment including the planet’s atmosphere, according to Reininghous. “The orbit is also polar but far more elliptical — 590 km times approximately 11,700 km. It has a period of 9.3 hours. The data return is approximately 10 percent of what we expect from the MPO.”

The European orbiter is much larger and more expensive, with Japanese probe budget being about a tenth the cost.

According to ESA, the mission took so long to build because in 2004, after about seven years of development, ESA suddenly realized that its orbiter’s thermal protection was inadequate, and required a complete redesign. To me, this is either outright incompetence (they knew from the start they were going to Mercury) or a clever way to extend the funding so that it provides an entire lifetime’s work for its builders. Think about it. Twenty-one years from concept to launch, then seven years to fly to Mercury, and then one to two years in orbit. That’s more than thirty years for this single mission.