Two mirrors, each small enough to fit in the palm of your hand, are set to change how we understand the cosmos.<\/p>\n
The launch window for NASA\u2019s Nancy Grace Roman Space Telescope<\/a> is about to open. The telescope\u2019s primary instrument is due to inform practically every area of astrophysics, but also tucked inside the telescope is a specialized coronagraph, an experimental apparatus that will attempt to directly capture starlight reflected off a planet\u2019s surface for the first time. It\u2019s an ambitious project that NASA hopes will pave the way for a space telescope<\/a> that can one day provide a glimpse of an Earthlike planet<\/a> orbiting a sunlike star.<\/p>\n That\u2019s a feat far beyond the power of current engineering\u2014hence taking the basic technique for a spin on Roman. \u201cWe\u2019ll test them in space for the first time, and we\u2019ll understand what work still is left to go,\u201d says Vanessa Bailey, an astrophysicist at NASA\u2019s Jet Propulsion Laboratory and instrument scientist for the coronagraph.<\/p>\n At its core, a coronagraph is just a science-minded sunshade that can block out the light of a bright star and reveal a fainter object otherwise lost in the glare. Such instruments have flown in space before\u2014both the Hubble and James Webb space telescopes carry coronagraphs. But Roman\u2019s is light-years more sophisticated than its predecessors, thanks largely to technology called adaptive optics, which deforms a telescope\u2019s mirror to cancel out these light distortions. It still faces a monumental challenge, though: NASA compares the task of Roman\u2019s coronagraph to photographing a firefly perched next to a floodlight\u2014from across the country.<\/p>\n \u201cAny little bit of starlight that gets in the wrong place could just destroy a whole portion of the image,\u201d says Margaret Turnbull, an exoplanet scientist at the SETI Institute, a nonprofit research organization in California, who leads a Roman coronagraph science team.<\/p>\n The technology is standard on advanced ground-based telescopes, including the Very Large Telescope in Chile and Hawaii\u2019s twin Keck Observatory. Here, adaptive optics monitors interference from the thick, shifting layers of Earth\u2019s atmosphere that muddy starlight, allowing observatories to capture sharper images.<\/p>\n Space telescopes haven\u2019t traditionally needed adaptive optics simply by dint of being beyond the atmosphere\u2019s interference, but they\u2019ve never even tried looking for old, cool planets illuminated solely by reflected starlight.<\/p>\n For Roman, the key to its success is those two palm-sized mirrors, each of which is rigged with approximately 2,300 tiny actuators that expand when a small jolt of electricity is applied, infinitesimally reshaping the mirror to reverse interference. It\u2019s the agency\u2019s first time ever flying active deformable mirrors in space.<\/p>\n