The Helio-STELLA is part of NASA’s STELLA (Science and Technology Education for Land/Light Assessment) instrument suite, designed as a low-cost, do-it-yourself handheld spectrometer focused on heliophysics applications. This accessible instrument allows students, educators, and citizen scientists to measure and analyze spectral data related to solar radiation.

Core Components

• Microcontroller: Thing Plus RP2040
• Spectral Sensor: AS7341 spectrometer (415-680nm range)
• UV Light Sensor: LTR390 UVA sensor (320nm)
• Display: 128 x 32 pixel OLED display
• Clock: PCF8523 real-time clock (set to UTC)
• Storage: Micro SD card for data logging
• Power: 2200 mAh rechargeable battery (~24 hours use from full charge)
• Connectivity: USB-C port for programming, data streaming, and charging

Features

• No-solder Assembly: Built entirely with qwiic/STEMMA-QT connectors
• Data Recording: Automatically logs measurements with timestamps and batch numbers
• User Interface: Simple pushbutton control to cycle through screens and toggle reference lamp
• Diffuser: Uses half a ping pong ball as a light diffuser for consistent measurements
• Software: Runs CircuitPython, a beginner-friendly programming language

Educational Value

Helio-STELLA serves as an entry point to various engineering disciplines:

• Embedded Systems Software Engineering: Open-source software written to be easily understood
• Electrical Engineering: Component connection and system testing
• Optical Engineering: Hands-on experience with wavelength detection and light measurement
• Mechanical Engineering: Assembly experience with 3D-printed components (optional)

Getting Started

1. Download the Helio-STELLA software package from: https://landsat.gsfc.nasa.gov/stella/helio-stella/
2. Install the Mu editor from http://codewith.mu
3. Follow the included instructions to load the software onto the microcontroller
4. Assemble the components using the included layout sheet and guide

Kit Contents

The complete kit includes all necessary electronic components, connection cables, battery, diffuser (ping pong ball), mounting tape, and comprehensive documentation. Assembly requires only basic tools like scissors, craft knife, glue stick, and clear tape.

Applications

The Helio-STELLA enables users to:

• Measure spectral characteristics of sunlight and other light sources
• Study light absorption and reflection across different wavelengths
• Learn about solar radiation and its properties
• Conduct comparative studies of natural and artificial light sources

This versatile instrument introduces users to scientific concepts in spectroscopy while providing valuable hands-on experience with electronics, programming, and data collection.