The STELLA (Science and Technology Education for Land/Life Assessment) project uses instruments that can be built with low-cost components and 3D printed housings to introduce NASA Earth observation technologies and provide authentic learning experiences for remote sensing education.   

STELLA 2023 summer intern uses a multimeter while building a STELLA instrument.
Mechanical and electrical engineering are combined when creating a STELLA. In this photo NASA high school intern Sabrina Pillai is showing a younger student how to troubleshoot a STELLA-1.1 using a digital multimeter. Photo credit: Mike Taylor
Karen Karker classroom pictures
A middle school student using a STELLA-1.1 spectrometer to see real-time spectral data, in this case the large rise in the near-infrared indicating plant health, using the STELLA-Dataviewer. Photo credit: Karen Karker
A woman leans against a multicolored wall, using it as a hard surface as she jots on a piece of paper. Behind her, a man uses a TV-remote-looking STELLA device. The backdrop is bright green grass and a blue sky dotted with white clouds.
Astronaut candidates test STELLA devices outside during a class focused on NASA Earth science missions. The experience gave them a better understanding of what affects spectral data measurements, and the importance of calibration of NASA instruments and data. Photo credit: NASA / Allison Leidner

STELLA Instruments 

STELLA Spectrometers 1.1, Q2, 2.0, Q
The STELLA spectrometer continuum. From left to right the STELLA-1.1, STELLA-Q2, STELLA-2.0, and the STELLA-Q. The spectrometers come in easy to put together builds that don’t require soldering and more advanced builds which require soldering and 3D printing. Photo credit: Paul Mirel

There are 3 types of STELLA instruments that can take measurements about the Earth’s environment. 

  • STELLA spectrometers measure energy across the visible and infrared portion of the electromagnetic spectrum, similar to measurements observed by the Landsat satellite. Data can be displayed using the STELLA-Dataviewer and analyzed to demonstrate how spectral data reveals information about our physical environment beyond what we can see such as vegetation health, moisture content, or mineral composition.
The STELLA-Dataviewer cycling through data
The STELLA-Dataviewer is able to display real-time data being collected by STELLA Spectrometers. This graph is cycling through measurements taken of vegetation with the visible spectral data being on the left and the near-infrared data being on the right. This shows the healthy dense vegetation reflecting high in the near-infrared. Note that the STELLA Dataviewer currently only works with the STELLA-1.0, 1.1, and 2.0 spectrometers.
  • The STELLA AQ (air quality) instrument provides the ability to gauge ambient air quality by measuring carbon dioxide (CO2) and particulate matter (PM).

  • The Helio-STELLA instrument measures incoming solar radiation throughout the visible light and Ultraviolet-A (UVA) spectrum, and is useful for understanding how radiation intensity varies across time and space.

STELLA for Outreach

The inspiration for the creation of the STELLA spectrometer line of instruments is Landsat. Using STELLA as an analog to Landsat you can show in real-time incoming measurements of reflected light and get across some of the basics about how and why Landsat and other highly accurate and precise remote sensing instruments benefit us.

Showing the difference in the near-infrared measurements between a healthy leaf and a dead or dying leaf and explaining why that’s important to agriculture and forestry is a simple and effective entry point to engage the audience’s curiosity. 

Michael Taylor (left) discusses Landsat and spectral signatures with NASA Headquarters employees including Bill Nelson, the NASA Administrator (second from left).
STELLA has helped people understand how Landsat and other remote sensing satellites work, why, how and what the benefits are to the data they collect. Michael Taylor (left) discusses Landsat and spectral signatures with NASA Headquarters employees including Bill Nelson, the NASA Administrator (second from the left). Photo credit: NASA
Bianca Poster AGU2023
Bianca is a student at RIT, graduating with her M.S. in Environmental Science in May 2024. She is using the STELLA and other devices and software to monitor biodiversity loss in Arctic ecosystems. Photo credit: Mike Taylor

STELLA for Education

STELLA introduces students to foundational remote sensing concepts by enabling them to build their own handheld instruments and use them to collect real-time measurements of reflectance from surfaces as well as measurements of air quality and incoming solar radiation. By building their own instruments, students learn first-hand about mechanical and electrical engineering concepts such as sensor assembly and light detection.

Students also learn about calibration concepts through the process of ensuring consistent and precise measurements from their STELLAs, and can learn basic programming skills by writing code to ingest and analyze the data.

STELLA for the Community

STELLA spectrometers provide users the ability to capture point-based reflectance observations in the visible (VIS) and near infrared (NIR) bands as well as temperature estimates from the thermal infrared (TIR) band over a variety of urban and vegetated land cover surface targets such as asphalt, bare soil, and grasslands.

STELLA reflectance data was measured against data collected in-situ from an ASD (Analytical Spectral Device) spectrometer using a white panel target under consistent light and target-sensor-illumination geometry conditions. Under these conditions, no significant differences in uncertainty were observed between the two data sources. Generally, the standard deviation of the data vary between 8-18% while the standard errors were found in the range of 3-6%, with the VIS bands having lower uncertainties than those in the red-edge and NIR bands.  

STELLA 2023 summer interns collect data in a corn field.
Two high school NASA summer interns, Christina Ballagh and Sabrina Pillai, collect STELLA-1.1 data over a corn field at the USDA Beltsville Agricultural Research Center with STELLA calibration/validation specialist, Jesse Barber using an ASD. Photo credit: Mike Taylor

While it is easy to obtain consistent measurements of reflectance from short and uniform canopy surface targets, limitations currently exist when collecting data over surfaces with heterogeneous texture properties and vertical canopy structure (e.g. tall corn and forest canopies), as an increase in uncertainty is associated with an increase in canopy height and spatial diversity. To obtain accurate reflectance time-series measurements, properties of the target land cover must be considered and care must be taken to ensure consistent target-sensor-illumination geometry and light levels between measurements.

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