At the end of March, a groundbreaking mission came to an official, if not scientific, end when the grant period of NASA’s Miniature X-ray Solar Spectrometer (MinXSS) CubeSat mission expired. Built by students at CU Boulder’s Laboratory for Atmospheric and Space Physics (LASP), these three successive CubeSat missions—MinXSS-1, MinXSS-2, and MinXSS-3 (also known as DAXSS)—were launched between 2016 and 2022 to study X-ray emissions from the Sun that can affect our communication and navigation systems.
The MinXSS mission not only opened new frontiers in our understanding of the intensity of the soft X-ray solar spectrum, a region that is of particular interest to scientists for observations of solar flares and active regions, but was also notable for its student involvement. The first two satellites—each about the size of a loaf of bread—were designed, built, integrated, tested, and operated by CU Boulder students. Over the course of the mission, more than 50 graduate and undergraduate students, and at least one local high-school student, participated along with LASP professionals.
Ultimately, the mission delivered unprecedented insights into the solar corona, solar flares, and their influence on Earth’s upper atmosphere. MinXSS also demonstrated the remarkable power of small satellites to perform high-quality solar observations, proving that major scientific advancements can be achieved with minimal cost and maximum ingenuity.
MinXSS-1, the first CubeSat science mission for NASA’s Science Mission Directorate, began its journey on May 16, 2016, with a deployment from the International Space Station. It was later named the 2016 Small-Sat Mission of the Year.
This movie of a CubeSat deployment from the International Space Station shows a compilation of photos taken by astronauts on May 16, 2016. The bottom-most CubeSat is the NASA-funded MinXSS CubeSat, built by the University of Colorado Boulder’s Laboratory for Atmospheric and Space Physics. MinXSS observed soft X-rays from the Sun. Such X-rays can disturb the ionosphere and hamper radio and GPS signals. (The second CubeSat is CADRE, built by the University of Michigan.) Credit: NASA
The first MinXSS gathered vital measurements of the Sun’s soft X-ray spectrum, which can disrupt the ionosphere, affecting radio and GPS signals. The mission also validated new solar flare models. MinXSS-2 followed in a polar, Sun-synchronous orbit, extending the solar observations during the solar cycle minimum period from December 2018 to January 2019.
The grant period may be over, but part of the mission lives on. MinXSS-3 is still flying aboard INSPIRESat-1 as the Dual-zone Aperture X-ray Solar Spectrometer (DAXSS). Operated by LASP’s partners at the Indian Institute of Space Science and Technology, it will continue to stream solar spectra data down to Earth, where it will be processed and analyzed. In 2022-2023 alone, MINXSS-3 delivered more than 130 solar flare observations.
Furthermore, the MinXSS missions have shown that the abundance of key elements like iron and silicon significantly decrease during flares by factors of two to four—a signature of a process central to solar physics flare theories. Even more astonishing, DAXSS revealed that solar flare plasma heats up during the flare onset phase before the flare’s impulsive phase, a game-changing breakthrough with implications for solar flare nowcasting.
As a trio, these CubeSats have sent more than 120,000 solar spectra down to Earth, helped train and foster the next generation of space scientists, and inspired several follow-on missions led by former MinXSS team members, further extending the legacy of small satellites making big science possible.
These missions include the Solar Corona Ejection Tracker (SunCET) CubeSat, led by James Mason, now at Johns Hopkins University Applied Physics Lab; the CubeSat Imaging X-ray Solar Spectrometer (CubIXSS), led by Amir Caspi, now at the Southwest Research Institute; and the Swift Solar Activity X-ray Imager Rocket (SSAXI-Rocket), led by Chris Moore, now at the Harvard-Smithsonian Center for Astrophysics.
The MinXSS CubeSats have redefined how we explore the Sun—one tiny satellite at a time.
By Tom Woods, LASP Senior Research Scientist and MinXSS Principal Investigator
Partners for the MinXSS-1 and MinXSS-2 missions have included the CU Aerospace Engineering Science (AES) department, Blue Canyon Technologies (BCT, Boulder), Colorado Satellite Services (CSS, Parker), NASA Goddard Space Flight Center (GSFC, Greenbelt), Southwest Research Institute (SwRI, Boulder), Naval Research Laboratory (NRL, DC), NCAR High Altitude Observatory (HAO, Boulder), Harvard & Smithsonian Center for Astrophysics, University of Alaska Fairbanks (UAF), with donated launch services for MinXSS-2 provided by Google/Planet with Spaceflight and SpaceX support. Additional partners for the InspireSat-1 mission have included the Indian Institute of Space Science and Technology (IIST) in India, the Nanyang Technological University (NTU) in Singapore, and the National Central University (NCU) in Taiwan, with donated launch services provided by the Indian Space Research Organization (ISRO).
Founded a decade before NASA, the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder 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.
