ESA unveils dual orbiter mission to Mercury


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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.

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One comment

  • Edward

    The article does not say much about the problems that they encountered: “He said that challenges in the design of solar panels, the thermal control systems and protective coatings, were the main cause of the lengthy development and several delays. ‘When we tested the thermal structure of the Mercury Planetary Orbiter [one of the two orbiters that form the mission], we learned that our thermal coverage is inadequate,’ Reininghous said. ‘The heat intake into the structure was such that we would not have covered it, reducing life time significantly. We had to completely rethink the system.'”

    I am going to side more on the “incompetence” side than the “greed” side. Generally, engineers and scientists like to finish and move on to the next project. For the scientists, getting stuck on a delayed project will limit the number of papers that they can write, and in a publish or perish world, that moves the scientists closer to the perish side of the equation.

    I am glad that I did not become a thermal engineer, because that is a difficult field. It is sometimes difficult to get the reality to work the way the theory said that it should. I have run into similar problems, where the thermal design needed adjustment after the thermal vacuum test showed that we were not getting the expected performance. However, I have not come across a situation where the thermal system had to be completely rethought; it is hard to say how they could miss by that much.

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