On a June morning this past summer, a small group of Techers who had recently completed their first year at the Institute huddled over a tarp, running sensor tests and filling their balloon with helium at a site near El Mirage in the Mojave Desert. The students were getting ready to launch GLOBO, a high-altitude balloon designed to track environmental data, which they had designed and built first as a class assignment and later as part of the Caltech Air and Outer Space (CAOS) club.
After months of work, it was time to see what their brainchild could do. Unfortunately, it was a blustery day in the desert. Winds gusted at more than 20 miles per hour, and temperatures soared above 100 degrees F. Even holding down the 100-cubic-foot balloon to fill it was challenging. After a long struggle against the wind, the team managed to fill the balloon, and team member Gavin John (who is also on Caltech's track team) took off running to launch the balloon and its precious cargo.
"When the balloon left the ground, and we saw our whole system float into the sky, I think that's when we realized that we had a reality. It wasn't just an idea anymore," says Priyanka Supraja Balaji, a GLOBO project lead who is now a second-year undergraduate at Caltech. "It was so inspiring to see what we were able to do as first years."
Co-lead Stephanie Wallen, also now a second-year student, agrees. "GLOBO is like our baby," she says. " Seeing it go up there after all the effort that we put into it was really rewarding."
In the end, GLOBO rose more than 20 kilometers into the atmosphere. It stayed aloft gathering data for about four hours before landing near Joshua Tree National Park, roughly 100 miles from its launching point.
GLOBO started off as a student project for CS 12: Introduction to Prototyping, a course taught in the winter 2025 term by graduate student Kevin Gauld (BS '24, MS '25). Students were tasked with designing and fabricating functional prototype systems that integrated mechanical, electrical, and software components to accomplish a specific task. CAOS co-leads Supraja Balaji and Wallen, who are both mechanical engineering majors with a lifelong interest in aerospace, met during the class and decided to team up for the project. In January, amid the smoky haze of the Los Angeles wildfires, Supraja Balaji and Wallen watched as people on campus and in the surrounding communities repeatedly checked air quality apps for updates. "Many of those apps lagged behind the rapidly changing conditions," Supraja Balaji says. "That revealed a critical gap in timely information."
"We knew we wanted to do something connected to that and also related to aerospace," Wallen adds. "We wanted our project to be something that could be useful."
For their project, they pitched a CubeSat-like high-altitude balloon capable of carrying multiple environmental sensors that could transmit data in real time, creating a low-cost, rapidly deployable platform to support focused climate action—from improving wildfire forecasting to guiding carbon capture and green infrastructure deployment. They got the green light. Other projects in the class included an automatic paint mixer, a complex soundboard, and a face-recognition system for opening doors. Throughout the course, students in the course gained experience working with different controllers for electronic components, and a variety of tools for prototyping their specific projects.
When the course concluded, Supraja Balaji and Wallen were ready to take GLOBO further. Gauld, their instructor, who was also one of the co-chairs of CAOS last year, encouraged them to bring the project to the club, whose members could help them refine the payload and prepare it for flight. After joining the club, the pair recruited a team of about 10 students, secured funding from the George W. Housner Student Discovery Fund, and gained access to materials and support from the Brinson Exploration Hub.
When complete, GLOBO consisted of a 3D-printed, 10-inch-wide cube compartment that housed a GPS module, a real-time clock, camera sensors for still images, a GoPro for video recording, altitude and pressure sensors, and a radio communication system. The payload also included a controller that managed sensors for carbon monoxide, methane, and volatile organic compounds.
Retrieval of the payload took some time. It ultimately touched down in an area of the desert that is off limits to the public. Through coordination with the military and environmental protection officers, Supraja Balaji and Wallen were able to collect the payload in early August. "Everyone was so supportive of our project," Supraja Balaji says. Surprisingly, the system had sustained very little damage.
Preliminary analysis of the data suggests that the sensors collected quality data and operated for the full duration of the flight.
"I think we accomplished our goal," Supraja Balaji says. "It was a proof of concept to show that we could develop a small high-altitude satellite that could collect data with a small university budget. Now we are designing a next-generation CubeSat payload that builds on what we learned."
CAOS has more in store for GLOBO: The club plans to develop a physics-focused payload and, inspired by NASA missions, aims to implement live-video transmission from the CubeSat. They also hope to make GLOBO's design modular, making it easy to swap out sensors. Finally, they hope to explore potential collaborations with industry and other universities.
Caltech students interested in learning about upcoming CAOS meetings and how to join are encouraged to email Supraja Balaji at [email protected].
