In mid-July, the Colorado Ultraviolet Transit Experiment (CUTE), a groundbreaking small satellite (SmallSat) built by the University of Colorado Boulder’s Laboratory for Atmospheric and Space Physics (LASP), transmitted its final data. The transmission—acquired over Antarctica by Neumayer Station III, a German research base operated by the Alfred Wegener Institute—marked the end of a mission that far exceeded expectations, continuing operations for nearly five years, well beyond its planned eight-month prime mission.
As the first NASA-funded ultraviolet astrophysics SmallSat ever launched, CUTE demonstrated that a spacecraft no larger than a cereal box could deliver high-value science, advance new instrument designs, and train the next generation of space scientists and engineers.
“CUTE set out to test whether a small satellite could tackle the kind of astrophysics normally reserved for much larger observatories, and it succeeded,” said CUTE principal investigator Kevin France, a LASP researcher and professor in CU Boulder’s Department of Astrophysical and Planetary Sciences. “The mission generated peer-reviewed discoveries, trained more than 40 early career scientists and engineers, mostly undergraduate and graduate students, and taught us invaluable lessons about how to build the next generation of small space missions. It has been a journey.”
Big science from a SmallSat
CUTE launched on September 27, 2021, from Vandenberg Space Force base as a secondary payload aboard an Atlas V 401 rocket. Of the 18 secondary missions manifested on this rocket, only four were successfully delivered for launch and flew, and of those four, only CUTE operated successfully on orbit, contributing to LASP’s record of 100% return on science for SmallSats.
Despite measuring just 35.5 centimeters (14 inches) long, the CubeSat carried a unique rectangular ultraviolet telescope, designed by LASP researcher and CUTE project scientist Brian Fleming, which provided more than three times the collecting area of a conventional telescope. The instrument was designed to study the atmospheres of exoplanets, particularly “hot Jupiters,” planets that are similar in size and density to our solar system’s gas giants, but much closer to their host star, making them extremely hot.
By observing these worlds as they passed in front of their host stars, CUTE measured subtle changes in the ultraviolet light emitted by those stars as it passed through the planetary atmospheres. Those observations allowed scientists to examine how atmospheres expand and escape into space under intense stellar radiation, a process that plays a fundamental role in how planets evolve.
“Understanding atmospheric escape is key to understanding how planets change over time,” France said. “CUTE allowed us to study those processes in real planetary systems beyond our own.”
During its mission, CUTE observed a growing sample of exoplanets and delivered the first detailed ultraviolet studies ever conducted from a CubeSat platform, contributing to scientists’ understanding of how atmospheric escape shapes planetary evolution across the universe, from giant gas planets to potentially habitable rocky worlds.
Among its most notable findings were observations of WASP-189b, an ultra-hot gas giant more than 300 light-years from Earth. CUTE data showed the planet’s atmosphere reaching temperatures of roughly 15,000 degrees Celsius (26,500 degrees Fahrenheit) and escaping into space at an estimated rate of about 400 million kilograms (nearly 900 million pounds) per second. The mission also studied planets that appeared to be losing little or no atmosphere, revealing that planetary evolution is more complex than scientists once thought.
A legacy of education and innovation
CUTE also helped train the next generation of space scientists and engineers by involving students in nearly every phase of the project: designing, building, testing, and operating the instrument in orbit, and also analyzing the scientific data it gathered.
While CUTE’s science mission has ended, its influence will continue. CUTE proved that CubeSats can make meaningful contributions to astrophysics, delivered valuable insights into the atmospheric evolution of exoplanets, and helped advance and mature instrument designs that are being used in future astrophysics missions.
France is now playing a key role in planning NASA’s Habitable Worlds Observatory, the next-generation flagship space telescope recommended by the 2020 Decadal Survey on Astronomy and Astrophysics. With a very large telescope and multiple instruments, HWO is being designed to identify Earth-like planets around Sun-like stars and search their atmospheres for potential signatures of life. The mission, which is expected to launch in the next 10 to15 years, will play a critical role in helping us understand our place in the cosmos.
By Sara Pratt, LASP Sr. Communications Specialist
Founded a decade before NASA, the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder (LASP) is revolutionizing human understanding of the cosmos. LASP is deeply committed to inspiring and educating the next generation of space explorers. From the first exploratory rocket measurements of Earth’s upper atmosphere to trailblazing observations of every planet in the solar system, LASP continues to build on its remarkable history with a nearly $1 billion portfolio of new research and engineering programs.
