After 8 years, Europe’s BepiColombo mission is on final approach to Mercury

历经八年，欧洲“贝皮科伦布号”任务进入抵达水星的最后阶段

The BepiColombo mission cleared a major milestone this week in the final stretch of an eight-year interplanetary voyage to Mercury, the hard-to-reach, scorching hot iron world at the Solar System’s innermost frontier. 本周，“贝皮科伦布号”（BepiColombo）任务完成了一个重要里程碑，进入了其八年星际航行的最后冲刺阶段。目的地是水星——这颗位于太阳系最内侧、难以抵达且酷热的铁质行星。

The robotic science mission, with a price tag of nearly $2 billion, is led by the European Space Agency with contributions from Japan and the United States. Since its launch in 2018, BepiColombo has spiraled closer to the Sun using a combination of plasma propulsion and a series of flybys of Earth, Venus, and Mercury. 这项耗资近 20 亿美元的机器人科学任务由欧洲航天局（ESA）主导，日本和美国也参与其中。自 2018 年发射以来，“贝皮科伦布号”通过等离子推进器与地球、金星和水星的一系列飞越，以螺旋轨道不断向太阳靠近。

The maneuvers changed the spacecraft’s velocity and steered it toward a final encounter with Mercury later this year. Next time it reaches Mercury, BepiColombo will be traveling at just the right speed for the planet’s gravity to capture the spacecraft into orbit. 这些机动动作改变了航天器的速度，引导它在今年晚些时候与水星进行最后一次“会面”。当它下次抵达水星时，“贝皮科伦布号”的速度将恰到好处，足以让水星的引力将其捕获并进入轨道。

Scientists working on interplanetary missions are accustomed to long waits for scientific payoffs. It took nearly 10 years for NASA’s New Horizons spacecraft to travel from Earth to Pluto. It turns out traveling to fleet-footed Mercury and then entering orbit requires more energy, or delta-v, than sending a probe to fly by Pluto. 从事星际任务的科学家们早已习惯了漫长的等待。美国国家航空航天局（NASA）的“新视野号”探测器从地球飞往冥王星耗时近 10 年。事实证明，前往运行速度极快的水星并进入轨道，比派遣探测器飞越冥王星需要更多的能量（即速度增量）。

That’s why BepiColombo’s trajectory required an unprecedented nine planetary flybys, or gravity assists, to set up for the chance to enter orbit around Mercury later this year. BepiColombo also launched with the most powerful electric propulsion system ever put into deep space, with four gridded ion thrusters to reshape its orbit around the Sun in between flybys. 正因如此，“贝皮科伦布号”的轨道设计需要史无前例的九次行星飞越（即引力助推），才能为今年晚些时候进入水星轨道做好准备。“贝皮科伦布号”还搭载了深空探测史上最强大的电力推进系统，配备了四个网格离子推进器，用于在各次飞越之间调整其绕日轨道。

BepiColombo is now a few months from reaching the end of its journey, and it no longer needs the plasma engines. On Thursday, BepiColombo jettisoned the section of the spacecraft containing the ion thrusters. This part of the spacecraft, called the Mercury Transfer Module, was responsible for generating power and providing propulsion for BepiColombo throughout the eight-year cruise. “贝皮科伦布号”距离旅程终点仅剩几个月，已不再需要等离子发动机。周四，它抛弃了包含离子推进器的舱段。这部分航天器被称为“水星转移模块”（MTM），负责在八年的巡航过程中为“贝皮科伦布号”提供电力和推进力。

But the propulsion module was no longer required, and BepiColombo needed to get rid of it before slipping into orbit in November. BepiColombo is unusual in that it is actually a stack of three spacecraft: the Mercury Transfer Module and the Mercury Planetary Orbiter, built by Europe, and the Mercury Magnetospheric Orbiter from Japan, nicknamed Mio. 但该推进模块已不再需要，且“贝皮科伦布号”必须在 11 月进入轨道前将其分离。“贝皮科伦布号”的独特之处在于它实际上是由三个航天器组成的堆叠体：由欧洲制造的“水星转移模块”和“水星行星轨道器”，以及来自日本的“水星磁层轨道器”（绰号 Mio）。

The separation of the propulsion module Thursday leaves the European and Japanese orbiters still traveling together. The two spacecraft will release from one another in December, soon after they arrive in their initial orbit around Mercury. The orbiters each have their own instruments for scientific observations at Mercury, while the transfer module is dead mass. 周四推进模块的分离，使得欧洲和日本的轨道器继续结伴飞行。这两个航天器将在 12 月抵达水星初始轨道后不久相互分离。两个轨道器各自携带用于水星科学观测的仪器，而转移模块则已成为无用的载荷。

A punishing environment

严酷的环境

Nothing like the controlled disassembly of BepiColombo has ever been attempted in such a harsh environment as the region of space near Mercury. Separation of the Mercury Transfer Module occurred 39 million miles (63 million kilometers) from the Sun, less than half the distance of Earth, with extreme temperatures and intense solar radiation. 在水星附近如此恶劣的太空环境中，从未尝试过像“贝皮科伦布号”这样受控的拆解任务。水星转移模块的分离发生在距离太阳 3900 万英里（6300 万公里）的地方，这不到地球到太阳距离的一半，且伴随着极端高温和强烈的太阳辐射。

Ignacio Tanco, head of inner Solar System mission operations at ESA, told reporters the challenge is “equivalent to launching a new spacecraft” with “considerable risk” of something going wrong. Letting go of the transfer module required the rest of the spacecraft take over power generation, propulsion and pointing, and thermal control, a significant concern flying so close to the Sun. 欧空局内太阳系任务运营主管伊格纳西奥·坦科（Ignacio Tanco）告诉记者，这一挑战“相当于发射一颗新的航天器”，且存在“相当大的风险”。抛弃转移模块后，剩余的航天器必须接管发电、推进、指向和热控功能，在如此靠近太阳的地方飞行，这令人十分担忧。

“This is something that we will only see after separation if it has worked, and we will be using several new sensors and mechanisms as part of the attitude control system,” Tanco said. Several of the mission’s science instruments, including its best cameras, were obscured by the propulsion module during the transit to Mercury. “It will be only upon release of the transfer module that these instruments will see first light,” Tanco said. 坦科表示：“只有在分离后，我们才能确认它是否运作正常。我们将使用几个新的传感器和机制作为姿态控制系统的一部分。”在前往水星的途中，该任务的几台科学仪器（包括性能最好的相机）一直被推进模块遮挡。坦科说：“只有在转移模块分离后，这些仪器才能迎来‘初光’。”

Early indications are everything went according to plan Thursday. The spacecraft executed preprogrammed commands to disconnect the transfer module and four springs pushed the two sections apart. Telemetry downlinked from BepiColombo showed the Mercury Planetary Orbiter’s solar arrays were generating power. 初步迹象表明，周四的一切都按计划进行。航天器执行了预编程指令以断开转移模块，四个弹簧将两部分推开。从“贝皮科伦布号”下传的遥测数据显示，水星行星轨道器的太阳能电池阵列正在发电。

“They were not seeing the Sun during the cruise phase,” said Elsa Montagnon, BepiColombo’s spacecraft operations managers at ESA. “We have confirmation that the power margins on the spacecraft are positive, that the solar arrays are recharging the batteries that were discharged during the separation. This is all excellent news.” “在巡航阶段，它们并没有直接面对太阳，”欧空局“贝皮科伦布号”航天器运营经理埃尔莎·蒙塔尼翁（Elsa Montagnon）说。“我们已确认航天器的功率余量为正，太阳能电池阵列正在为分离过程中耗尽电量的电池充电。这都是极好的消息。”

The path to Mercury hasn’t always been easy. BepiColombo’s ion thrusters lost partial power in 2024, and engineers extended the mission’s cruise by a year to account for the loss of thrust. BepiColombo has covered more than 6 billion miles (10 billion kilometers) since departing Earth, and is now on track to maneuver into orbit around Mercury on November 21. 前往水星的道路并非一帆风顺。“贝皮科伦布号”的离子推进器在 2024 年部分功率受损，工程师们因此将任务巡航时间延长了一年，以弥补推力的损失。自离开地球以来，“贝皮科伦布号”已飞行超过 60 亿英里（100 亿公里），目前正按计划于 11 月 21 日进入水星轨道。

“It’s a very ambitious mission,” said Santa Martinez, ESA’s mission manager for BepiColombo. “Mercury is a challenging destination. It’s very difficult to reach. It’s very difficult to operate at because of the extreme environment so close to the Sun. But what makes this mission really unique is that for the first time in space exploration, we are bringing two spacecraft to the vicinity of the planet, and we are going to put them in orbit around this mysterious body. This is going to bring to humanity and to the scientific community unprecedented views of the Mercury planet, and it’s going to open a new chapter in our understanding of the Solar System.” “这是一项雄心勃勃的任务，”欧空局“贝皮科伦布号”任务经理圣塔·马丁内斯（Santa Martinez）说。“水星是一个充满挑战的目的地。它非常难以抵达，且由于靠近太阳的极端环境，在那里进行操作也非常困难。但这项任务的独特之处在于，这是太空探索史上首次将两颗航天器带到该行星附近，并将它们送入这颗神秘天体的轨道。这将为人类和科学界带来前所未有的水星视角，并开启我们理解太阳系的新篇章。”