In 2013, Bryan Chan, Ved Chirayath, Ashish Goel, Tyler Reid, and Paul Tarantino took on the challenge of flying a stratospheric weather balloon over the Grand Canyon in Arizona. Initiated by Ved’s dissertation research in fluid lensing, this mission built on our experience from our first balloon flight in 2011. This new balloon mission had more ambitious goals:
- To perform fundamental scientific research in the area of fluid lensing.
- To further test the navigation capabilities of commercial Global Navigation Satellite Systems (GNSS) in smartphones.
- To take better pictures than in our first mission using some lessons learned.
- To fly over the Grand Canyon while successfully doing (1-3).
This mission was equipped with several cameras to collect data for the fluid lensing experiment which had the added benefit of documenting the mission. We had a GoPro Hero 3 and Sony Camcorder each taking HD video as well as a Samsung Galaxy Note II set to take still pictures. For the GNSS experiment, the system was equipped with an unmodified smartphone provided by Broadcom. We worked with Dr. Frank van Diggelen, V.P. of GPS Technology at Broadcom as well as a Consulting Professor at Stanford University, to achieve this part of the mission. Broadcom now makes it standard for its chips to work above 60,000 feet (as long as you are sub-sonic!). On this flight, the GNSS reported a maximum altitude of 98,816 feet (30.1 km) and never once lost the ability to compute our position. This Galaxy Note II was equipped with a GPS + GLONASS + QZSS receiver. These devices were housed in a 3D printed structure printed by a Stratasys uPrint. Time on the 3D printer was kindly provided by the Stanford Space Systems Development Lab (SSDL) and Professor Andrew Kalman.
The 3D printed structure was then wrapped in soft foam for impact absorption and denser styrofoam for thermal insulation. This payload box was then tied to a radar reflector, parachute, and finally the weather balloon itself. The radar reflector gives high visibility to aircraft and is a device in place for safe operations in the airspace. The parachute is in place for the descent back to Earth. As the balloon ascends, the atmosphere gets thinner and the balloon expands. At some point the balloon can no longer expand due to limitations of the latex material and it simply bursts. The parachute is in place to slow the descent and ultimately give our equipment a gentle return to Earth.
Cell coverage in the area of the Grand Canyon was not as shown on some service providers websites. As a result of this, we lost contact with the balloon payload and did not hear from it again. We did have a backup transponder onboard which broadcast in the amateur radio band, but this proved too faint to be of use. The payload ran out its batteries and lay dormant in the desert for nearly 2 years. By some miracle, a hiker found our payload but unfortunately all identifying marks had worn off or blow away. It seems that cattle trampled our payload at some point, destroying most of the styrofoam box and 3D printed housing. By a twist of fate, this hiker worked for a cell service provider and determined how to contact us based on the sim card in the phone and all items were kindly returned. Amazingly, even though subjected to the harsh desert conditions for 2 years, all data was recovered. The Samsung phone and Sony Camcorder still work to this day. The GoPro unfortunately does not and was clearly more weathered than the other equipment. What seems to have happened is that the GoPro broke free upon landing, projecting out on the desert floor to lay exposed and bake in the Arizona sun. The other equipment was protected by the foam insulation and as a result sustained much less damage.
A post-flight analysis showed that all systems functioned as intended resulting in a collection of amazing photos and videos. The Smartphone GNSS unit also functioned beautifully, not only working above 60,000 feet out of the box but also never losing lock, even during the initial free fall which a problematic area on our first Gilroy balloon mission. Analysis of the data also showed us how lucky we were. The balloon happened to land near someone’s house in a very remote region of the desert. In fact, in the violent spin of the descent we caught a picture of the very house of the person who found our balloon.
The video of the mission (compiled by Bryan Chan) went viral and gained this project a lot of media attention. Please see the team’s interview with CNN, Bryan’s interview with the CBC, the article in the Washington Post, and coverage in the BBC, The New York Times, IFLScience, and PC Magazine.