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A spacecraft carrying a piece of equipment built at Southwest Research Institute in San Antonio is nearing the planet Mercury. On board the BepiColombo spacecraft is Strofio, a neutral mass spectrometer specifically designed to sample the sparse exosphere around Mercury. The spacecraft is a joint mission of the European and Japanese space agencies and was launched in 2018.
From a recent press release from SWRI:
Last week, the BepiColombo spacecraft completed a major milestone ahead of Mercury orbit insertion and the start of the science mission early next year, releasing the two orbiters from the transfer module. When the orbiters separated from the transfer module, the protective covers were removed from Strofio.
Strofio is a neutral mass spectrometer specially designed to sample the sparse exosphere around Mercury, measuring the particles emanating from its surface. The basketball-sized instrument weighs just over 7 pounds and promises scientists a better understanding of the surface composition and space environment of Mercury — the smallest rocky planet of the solar system orbiting closest to the Sun.
Orbiting Mercury with a spacecraft is extremely challenging and complicated — and BepiColombo will be only the second mission to do so, following NASA’s MESSENGER spacecraft (2011 to 2015). As the spacecraft travels toward the Sun, solar gravity forces it to pick up speed. Multiple gravitational assists from Earth, Venus and Mercury are then needed to slow down the craft. Rather than the four to five months it would take for a flyby mission, an orbiting mission takes almost 10 years in a looping trajectory to achieve the precise speed needed to enter orbit around the rocky planet. It is easier to orbit Jupiter than Mercury even though Jupiter is much farther away.
TPR’s Jerry Clayton recently interviewed Staff scientist Dr. Frederick Allegrini, who will help analyze that data that Strofio collects.
Clayton: What will Strofio do once the BepiColombo spacecraft places it in position?
Allegrini: Strofio is an instrument that will measure the composition of what we call the exosphere of Mercury. Mercury is a small planet. It doesn't have an atmosphere like the Earth. It doesn't have enough gravity to hold an atmosphere, but there is still material that is above the surface that comes from the surface, Strofio will go through that material and measure its composition.
Clayton: Why is Mercury so difficult to reach and to get into and orbit around?
Allegrini: The problem is when you get to Mercury, you have gathered so much speed that it is extremely hard to slow down, and so that's why it is actually difficult to get to Mercury — because you gain so much energy going towards the sun, and then you have to brake and slow down so that you can go into orbit around Mercury. So that's the part that is difficult.
Clayton: What are you hoping that Strofio may be able to tell us about Mercury that we don't already know?
Allegrini: So we don't know much. It's the planet we know the least from the solar system. Going there with new instrumentation, different instrumentation that had been on previous missions. The BepiColombo mission will study the planet in detail, and it's got two spacecraft. One will study more Mercury and its interior, and the other one will study what we call the magnetosphere, which is kind of the environment around Mercury that is affected by the Sun and Mercury itself. What we'll learn Strofio, for example, is the composition of the surface of Mercury, of some of the surface, because the material that comes into our instruments came from the surface directly. So we will sample a little bit of Mercury's surface and determine what composition is. There are other instruments that do remote sensing, so they measure light or different things coming from the surface, but from a distance perspective. And by combining all of that information, we'll know more about the surface of Mercury and what its composition is and the interior.
Clayton: It will have taken almost eight years to get to Mercury. How exciting is it to finally be able to make your measurements?
Allegrini: Well, from a scientist's perspective, it's exciting, and I'm sure from an engineer's perspective too. It's a long journey, but now we're really eager to collect data and start looking at the science that we propose to do with that instrument and that mission, so it's an exciting point. The work that was prior to launch was very intense. So getting to Mercury is a lot of fun because now we're going to see all the return from that in personal investment and hard work, and we'll we'll be able to do some exciting science, and I expect that we will find things that we didn't expect. That's often what happens when you send new instrumentation to a new place. You always find something that you didn't expect, and then you have to explain, and you learn something. So that is really the work of a scientist, and it's exciting
