As the sun bathes the neighborhood in the soft morning glow, a high schooler embarks on her daily walk to school. However, today is different. Her curiosity is piqued by an unusual patch of greenery in her neighbor’s yard. Something about those plants doesn’t quite sit right with her. They appear less vibrant than she expects healthy plants to be.
Intrigued, she decides to investigate with the help of a remarkable companion, STELLA. STELLA isn’t much larger than a smartphone, but its capabilities are out of this world. With a press of a button, she aims STELLA at the foliage, and a small screen springs to life, displaying an array of numerical measurements—temperature, humidity, and light intensity, to name a few. These numbers, like vital signs during a checkup, hold the key to understanding the plant’s overall health.
You might think you’ve stepped into a scene from “Star Trek” with its fictional tricorder, but this is real-life science in action. STELLA, which stands for NASA’s Science and Technology Education for Land / Life Assessment, is a genuine tool designed for students, educators, and citizen scientists. It’s a handheld, do-it-yourself gizmo capable of scanning, recording, and analyzing environmental features, including plant health. While not quite on par with the tricorder, STELLA shares some intriguing similarities with its sci-fi counterpart.
For example, STELLA can measure leaf temperature, air temperature, and the difference between them, offering insights into a plant’s hydration levels. Paul Mirel, the chief engineer behind the project, explains how these measurements can reveal crucial information about a plant’s well-being. Since 2019, NASA’s Landsat science project has supported the development of STELLA at the Goddard Space Flight Center in Maryland. It serves as an invaluable tool for demonstrating how Landsat satellites’ imaging instruments work.
Mirel also notes that STELLA’s data on light intensity can act as a proxy for a plant’s photosynthetic activity. Healthy plants primarily absorb visible light and reflect near-infrared light, while unhealthy or sparse vegetation does the opposite. The ratio between these two types of light is known as NDVI—the normalized difference vegetation index.
NASA’s Earth-observing satellites can measure NDVI on a global scale, providing critical data for farmers and foresters to assess crop and tree health, particularly in times of drought and high temperatures.
While STELLA’s readouts are far simpler than Landsat’s, the goal isn’t to replace satellites. What makes STELLA invaluable is its ability to empower individuals to make these measurements themselves. Earth scientist Allison Leidner, a program manager in NASA’s Earth Science Division, emphasizes that STELLA offers a rough glimpse of what satellite data looks like and how it aids our understanding of Earth.
“STELLA presents a great opportunity to integrate scholarship and education with an instrument that can give us publication-quality data on plant physiology and health at prices affordable to public schools and private individuals,” adds Manuel Lerdau, an ecologist at the University of Virginia.
In a testament to its educational potential, two high school interns at NASA Goddard dedicated their summer to building 40 STELLA devices. Christina Ballagh worked on the circuit boards, while Sabrina Pillai tackled the screens. These newly assembled STELLAs will be loaned out for educational purposes, reaching schools across the United States.
Instructions for building STELLA are freely available online, along with three different models. The simplest requires no soldering or 3D printing and can be assembled with tongue depressors. The total cost for all components can be less than $200.
The mission is clear—to democratize instrumentation. STELLA’s GitHub public forum offers lesson plans and best practices, making it a valuable resource for educators. Karen Karker, an instructional support specialist, praised STELLA as a fantastic visual aid for the classroom.
As Manuel Lerdau aptly puts it, “Students can use STELLA to understand the world around them, to study the living and the built environment, and to take the steps toward changing the way we treat our planet.” STELLA is not just a device; it’s an instrument of change, nurturing the next generation of Earth’s caretakers.