Work has begun on an ambitious new mission that will carry a cutting-edge 2.5m telescope high into the stratosphere on a balloon. Scheduled to launch in December 2023 from Antarctica, ASTHROS (short for Astrophysics Stratospheric Telescope for High Spectral Resolution Observations at Submillimeter-wavelengths) will spend about three weeks drifting on air currents above the icy southern continent and achieve several firsts along the way.
Managed by NASA's Jet Propulsion Laboratory, ASTHROS observes far infra-red light (light with wavelengths much longer than what is visible to the human eye). To do that, ASTHROS will need to reach an altitude of about 130,000ft – roughly four times higher than commercial airliners fly. Though still well below the boundary of space (about 100km, above Earth's surface), it will be high enough to observe light wavelengths blocked by Earth's atmosphere.
The mission team recently put the finishing touches on the design for the observatory's payload, which includes its telescope, its science instrument, and sub-systems such as the cooling and electronic systems. In early August, engineers at JPL will begin integration and testing of the sub-systems to verify that they perform as expected.
While balloons might seem like antiquated technology, they offer NASA unique advantages over ground- or space-based missions. NASA's Scientific Balloon Program has been operating for 30 years at Wallops Flight Facility in Virginia. It launches 10 to 15 missions a year from locations around the globe in support of experiments across all of NASA's science disciplines, as well as for technology development and education purposes.
Balloon missions not only have lower costs compared to space missions, and also have shorter times between early planning and deployment, which means they can accept the higher risks associated with using new or ‘state of the art’ technologies that haven't yet been deployed in space.
These risks may come in the form of unknown technical or operational challenges that can impact a mission's science output. By working through these challenges, balloon missions can set the stage for future missions to reap the benefits of these new technologies.
JPL engineer Jose Siles, project manager for ASTHROS, said: “Balloon missions like ASTHROS are higher-risk than space missions but yield high rewards at modest cost. With ASTHROS, we are aiming to do astrophysics observations that have never been attempted before. The mission will pave the way for future space missions by testing new technologies and providing training for the next generation of engineers and scientists."
ASTHROS will need a big balloon: When fully inflated with helium, it will be about 400ft wide, or about the size of a football stadium. A gondola beneath the balloon will carry the instrument and the lightweight telescope, which consists of a 2.5m dish antenna as well as a series of mirrors, lenses, and detectors designed during flight, scientists will be able to precisely control the direction that the telescope points and download the data in real-time using satellite links.
A division of Caltech in Pasadena, JPL manages the ASTHROS mission for the Astrophysics Division of NASA's Science Mission Directorate. JPL is also building the mission payload. The Johns Hopkins Applied Physics Laboratory in Maryland is developing the gondola and pointing systems, while the 2.5m antenna unit is being built by Media Lario S.r.l. in Lecco, Italy.
The payload cryocooler was developed by Lockheed Martin under NASA's Advanced Cryocooler Technology Development Program and NASA's Scientific Balloon Program and its Columbia Science Balloon Facility will provide the balloon and launch services.
ASTHROS will launch from McMurdo Station in Antarctica, which is managed by the National Science Foundation through the US Antarctic Program. Other key partners include Arizona State University and the University of Miami.