Even in the vast expanse of space, the smallest detail can make a big difference. A soon-to-launch experiment from MIT shows how. The Deformable Mirror Demonstration Mission (DeMi) CubeSat will put a new telescope mirror to the test before the year is out. It could equip future satellites with the tools to find the exoplanets most likely to contain life.
What makes this mirror exceptional can’t be seen until you get up close. Behind its reflective surface sit 140 tiny actuators that’ll let the mirror bend and adapt to get clearer light readings from stars outside our solar system.
These changes are needed because when you’re in orbit, conditions can be rough. One side of your satellite can be burning hot in the sun, while the other can be freezing cold. As the temperature changes, the parts change size and move. Rotating and thrusting can make things vibrate as well. “All of these disturbances make tiny little speckles on the pictures that you’re taking,” says Kerri Cahoy, an associate professor of aeronautics and astronautics at MIT.
To fix this, the mirror can sense errors in the picture, and bend to correct them. It does this by analyzing the light as it hits the mirror. Printed circuit boards send signals to rods, which adjust the shape of the mirror accordingly. It doesn’t need to move a lot: we’re talking 10 to 20 nanometers. But these slight changes could combat any distortion in the light the telescope is picking up. “One nice thing about this type of technique is that the contrast is so good,” says Paula do Vale Pereira, an MIT PhD student and mechanical lead on the project.
Researchers could use a larger version of this deformable mirror to take better images of stars, block out the light from a star, and image nearby exoplanets. The mirror will also help them pick up the light more clearly so they can look at the spectrum of the gases the planet is giving off. This provides information about the composition of its atmosphere, says Cahoy. That could give us a clearer picture of the things we are observing outside our solar system.
While this is just a test to ensure the mirror will work in space, future missions using larger versions will look for gases like carbon and traces of water for hints of life.
The technique might be new in space, but it has been used on Earth for years to fight the distortion caused by our own atmosphere. Ground-based observatories have mirrors that adapt many times per second in response to readings of how winds and atmospheric gases are affecting the light.
Eventually, the data from this small experiment will inform future space-based telescopes. Researchers would love the next one “to have the capability of figuring out if there’s life on another planet by looking at the spectra of a planet or another star,” says Cahoy.
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