Thursday, May 16, 2024

Joint Japanese-European Mercury Probe Having Troubles

On October 20, 2018, the European Space Agency (ESA) in partnership with the Japanese Aerospace Exploration Agency (JAXA) launched probe to investigate planet Mercury, the innermost planet of the solar system with several flybys culminating with going into orbit around the little planet for longer observations. The probe, called BepiColombo, launched atop an Ariane 5, now retired. 

It was reported today that the probe's thrusters have malfunctioned and the agencies aren't yet sure if it will be able to achieve orbit. 

The BepiColombo spacecraft ... could be feeling the heat even before it reaches its destination: Mercury. Thanks to a glitch, the spacecraft's thrusters are no longer operating at full power. The team has yet to determine how this will impact upcoming maneuvers, like a Mercury flyby set for later this year.

Destined to become just the second mission to orbit Mercury when in December 2025, BepiColombo is composed of two probes and something called the "Mercury Transfer Module" that scientists hope will answer many perplexing questions about the smallest planet in our solar system. (To be clear, BepiColombo has performed Mercury flybys before, but is yet to actually enter Mercury's orbit.)

The Mercury Transfer Module is intended to address questions like how a planet as blisteringly hot as Mercury could have ice in its polar craters. It implies the conduction of heat in the planet's surface is so low that thermal equilibrium favors heat radiating away from the planet over being conducted to the poles. Among other questions. 

The 48-million-mile-long (77-million-kilometer-long) journey to Mercury is far from straightforward for BepiColombo; the spacecraft will make a total of nine planetary flybys before being inserted into the relatively tiny planet's orbit. And, as ESA reports, the glitch experienced by the spacecraft on April 26 has complicated this journey further.

BepiColombo experienced the glitch as it was preparing for a maneuver to set it up for its fourth flyby of Mercury on Sept. 5, 2024. The problem centers on the Mercury Transfer Module, the leftmost module in this diagram.

The Mercury Transfer Module is equipped with solar arrays and an electric propulsion system used to generate thrust. As the spacecraft was about to begin its April 26 maneuver, however, operators found that the Transfer Module had failed to deliver enough electrical power to its thrusters.

As soon as the fault was identified, ESA operators set about rectifying it. By May 7, the team had restored power to the thrusters such that they reached 90% full capacity, but the power available from the Mercury Transfer Module is still below what it should be. This means BepiColombo is continuing to operate without its full thrust.

The ESA hasn't yet determined if the thrusters can still perform the job they're required to do, saying the BepiColombo team's main priorities are to keep the spacecraft's thrust stable at its current sub-optimal levels, and to work out how the spacecraft will handle upcoming maneuvers at less than full propulsion. The mission is scheduled to continue through 2028, or 10 years in space, with flybys set for Sept. 5 this year, with a fifth and sixth flyby set for Dec. 2, 2024, and Jan. 9, 2025. After that final flyby is when the spacecraft is to go into orbit around Mercury. If the thrusters can do that.


  1. One suspects that DEI is also rampant in Europe, so if they made the RCS, then that might explain the problem.

  2. Maybe someone can call project management to talk about their extended warranty...

  3. Operators were able to restore 90% power to thrusters. Yet still, module may not enter orbit.

    Is there not a built-in margin? Why come the missing 10% is enough to jeopardize the entire mission? Seriously, launch with module to Mars. Bad news, guys, we're only able to restore to 90%, the mission fails unless we can squeak out that meager 10%.

    Or, 90% is sufficient but there remains another reason why orbit may not be achieved.
    The way the article is written it is not clear if 90% power to thrusters is the sole thing possibly preventing entering the intended orbit.

    1. I understand the weight penalty. Ya want to engineer the slimmest, lightest to meet requirements. But is 10% - or more likely, 115% design for that critical system - outside the specs?