A Helium Bubble of Breakthroughs: Analyzing the BARREL (Balloon Array for Radiation-belt Relativistic Electron Losses) Mission

By Bryan D. Milstead

Across decades of innovation, NASA has created some truly amazing apparatuses to drive forward the initiative for space discovery. For example, the “SLS” (Space Launch System) comprises a plethora of dome sections, rings, & is even covered with an orange spray-on foam to insulate its cryogenic propellants (Mohon, 2024, para. 5). Other mechanisms like the “SuperCam” examine martian rocks with a complex camera-, laser–, & spectrometer framework to ensure images of remarkable quality (Melody, 2024, section 4) . What if there was a NASA platform that flies hundreds of thousands of feet into the air & can be as wide as a football stadium, yet possesses a thickness similar to that of a sandwich wrap (Adkins, 2024, para. 4)? 

Introducing the scientific balloon, an efficient & low-cost method of sending scientific instruments into suborbital spaces. They are the perfect way for helping NASA & the broader academic community further their knowledge about our Earth as well as our solar system. In this technical report, we will explore the BARREL (Balloon Array for Radiation-belt Relativistic Electron Losses) scientific balloon mission & elaborate on its objectives. Additionally, a multifaceted analysis of BARREL instrumentation & stakeholders will be conducted, in order to evaluate the implications of this mission from a holistic perspective. 

NASA’s “BARREL” mission started in 2013 & consisted of multiple, suborbital balloon campaigns over Antarctica. All of these were deployed to detect charged particles that exist in large atmospheric capacities, known formally as Van Allen belts (Cermak, 2023, para. 3). For some context, the Earth has a magnetic field called the “magnetosphere” which shields our planet from solar radiation, but also traps these high energy particles. Therefore, astronauts who travel through these Van Allen belts (as well as their equipment) are susceptible to overwhelming bouts of solar activity, risking the integrity of a mission &, more importantly, human life (Cermak, 2023, para. 4). By utilizing highly precise X-ray instruments, scientists were able to better understand atmospheric electron activity whilst simultaneously improving space weather forecast accuracy (NASA [National Aeronautics and Space Administration], 2023). 

Missions like BARREL are extremely sophisticated & must be handled with a just as intricate level of precision. It was precisely NASA’s Wallops Flight Facility that played an integral role in the success of this mission. A magnetometer component of the BARREL scientific balloons was directly developed with funding from Wallops’ Undergraduate Student Instrument Program, showcasing the facility’s commitment to providing opportunities for the budding generation of scientists & engineers (Kaiser, 2024, caption 2). On a broader scale, the Wallops Flight Facility leads the majority of the scientific balloon initiative, as they manage NASA’s Scientific Balloon program & average 10-15 flights per year from launch sites across the globe (Adkins, 2025, para. 1). 

Antarctica may not seem like the optimal launch site considering how it is the coldest, driest, & windiest continent – however, it was actually very attractive to BARREL scientists (literally!) (AdventureSmith Explorations, n.d., para. 4). Because Antarctica is adjacent to the South Pole (where the Earth’s magnetic field is the strongest, other than the North Pole), this allowed the scientific balloons’ magnetometers to most effectively perform their duties. Moreover, the remote location & wind conditions of Antarctica ensured that the scientific balloons remained airborne for weeks/months without interference from extenuating circumstances (Littleton, 2025, para. 20). With regards to the specificities of the BARREL mission, it released 20 eight-story-tall balloons, traveling all across the atmosphere of the lower southern hemisphere (Garner, 2013,  para. 1). Something interesting about BARREL was its interconnectedness with other NASA initiatives like the Van Allen Probes, which worked in conjunction with each other to observe Van Allen belt occurrences & subsequently track electrons that diffused from the belts. After the scientific balloons floated the time necessary to collect data, each flight was terminated & both the payloads & balloons were recovered (NASA Goddard Space Flight Center, n.d.). 

Let’s now shift our focus to the instrumentation that made this mission possible; particularly, the spectrometer. Spectrometers are scientific devices that measure the properties of electromagnetic radiation in different sections of the electromagnetic spectrum (tec5, 2025, para. 7). Once the BARREL balloons achieved an optimal altitude of 30-35 km, their attached NaI (sodium iodide) spectrometers would be able to measure the X-rays produced by relativistic electrons as they extrude from certain crevices of the Van Allen Belt (Millan, n.d., para. 2). We will explore the intricacies of these spectroscopic apparatuses in the next paragraph. 

Sodium iodide spectrometers possess a wide range of intricate parts, with the most notable one being, well, sodium iodide (chemically abbreviated as “NaI”). As mentioned previously, the solar energy emitted from the Sun’s corona are harmful x-rays that alter the functionality of space devices & endanger the astronauts who use them (NASA Goddard Space Flight Center, 2014, para. 3). X-rays emit “ionizing” radiation which strikes the internal elements of the spectrometers, causing immediate ionization of the sodium iodide (in crystalline form) (Ortec, n.d., para. 4). Visible light photons are given off, passing through the crystal & entering a photo-multiplier tube (PMT), where electrons are released via the photoelectric effect. This scintillation is then converted into an electrical pulse, corresponding to different levels of radiation & subsequently analyzed by scientists (Mirion, n.d., para. 2). Spectrometers such as these face one major drawback: hygroscopicity (tendency to absorb water from the air), which is why the sodium iodide crystals are placed in “hermetically sealed housing”. However, this adds cost & complexity into the entire design of the spectrometers (Nuclear System, n.d., para. 4). 

Figure 1. Radiation Detection Scintillation Detectors

Note: One can observe how the electromagnetic radiation immediately hits the sodium-iodide crystal, causing light to travel and multiply throught the optical window.

The hard work & constant days of testing were not in vain. BARREL researchers acquired comprehensive results related to the behavior of atmospheric electrons, as well as regarding the effects of geomagnetic storms on digital processes here on Earth. Thanks to the numerous science balloons that repeatedly orbited the South Pole for several weeks, BARREL researchers collected extensive electron levels to create a well-rounded data set (literally!).

A topic like electromagnetic radiation can seem “unproductive” outside of academia. However, it was actually crucial to the processes of various stakeholders, including astronauts & citizens. For the former, BARREL improved space weather forecasting to prioritize the safety of astronauts against unforeseen geomagnetic storms/solar flares (National Weather Service, 2023, para. 4). For the latter, BARREL data helped scientists understand the factors involved in disrupting telecommunications & GPS signals which, in turn, encouraged more robust satellite design (Garner, 2013, para. 2). 

NASA has continued to engage in missions similar to BARREL to further NASA’s vision of understanding helio-physical effects on our solar system, simultaneously mitigating the hazards present as humans traverse the heavens (NASA, 2023, pts. 8 & 9). GUSTO (Galactic/Extragalactic ULDB Spectroscopic Terahertz Observatory), for example, launched in December 2023 & clearly defined the nebulous properties of interstellar gas in the Milky Way (metaphorically & literally). While scientific balloons might not be the most grandiose NASA apparatus, they serve as a testament to Aristotle’s quote, “The whole is greater than the sum of its parts.” Without each data point & meticulous balloon launch, NASA would not be able to fulfill its broader goal for developing a multifaceted perspective on our universe. 

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