The James Webb Space Telescope may catch the eye this summer, but next year keep an eye out for NASA’s ASTHROS (Astrophysics Stratospheric Telescope for High Spectral Resolution Observations at Submillimeter-wavelengths) instrument.
ASTHROS is not a space telescope or a ground telescope but something in between, hovering in the stratosphere. NASA intends to fly the instrument at an altitude of 130,000 feet (40,000 meters) via a balloon larger than a football field, deploying it over Antarctica for a period of up to go up to four weeks. The advantage of flying a telescope at this altitude is that it greatly reduces interference by earth’s atmosphere — a crucial aspect of ASTHROS’ mission.
The telescope will study an unusual phenomenon called stellar feedback, a process by which life stars and the dying fan the clouds of gas and dust around them. Normally, this creates an environment that favors the birth of stars. But in some extreme cases, too much stellar feedback can actually prevent new stars from being born. ASTHROS will scan star forming regions in the Milky Way and create 3D maps cataloging the movement of gas inside these regions, NASA officials said in a statement.
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To do this, the instrument must observe light in the far infrared wavelengths. Ground-based telescopes cannot see this light because it is blocked by the densest part of the atmosphere, the troposphere. But at an altitude of almost 25 miles (40 kilometers), ASTHROS will be in the less dense stratosphere, allowing it to take sharp images in the far infrared range.
Engineers face a unique set of design challenges for this instrument. To begin with, the whole telescope must be extremely light to be carried by the balloon. But it must also be rigid enough that the shape of the 8.2-foot (2.5 m) nine-piece mirror will not warp or move more than 0.0001 inch (2.5 micrometers), smaller than the width of a human hair. If the mirrors misaligned even to this slight degree, they would not be able to produce clear images.
NASA commissioned Italian optical company Media Lario to design ASTHROS; the company had previously developed lightweight telescope mirrors used in the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile.
“I think this is probably the most complex telescope ever built for a high-altitude balloon mission,” Jose Siles, ASTHROS project manager at NASA’s Jet Propulsion Laboratory, which manages the mission, said in the release. . “We had specifications similar to a space telescope but with a tighter budget, schedule and mass. We had to combine techniques from ground-based telescopes that observe in similar wavelengths with manufacturing techniques advancements used for professional racing sailboats. It’s quite unique.”
ASTHROS is currently under construction and will launch from NASA’s Long Duration Balloon Facility in Antarctica no earlier than December 2023.