Project Overview

The "Tornado Atmos-Probe" is a citizen-science aerospace project designed to capture high-resolution meteorological data from the interior of severe convective storms. Utilizing LoRa (Long Range) telemetry, a modified Estes Loadstar II rocket carries a suite of high-precision sensors into the troposphere to measure pressure drops, humidity spikes, and rapid thermal shifts. By combining dual-redundant microSD logging with real-time RF transmission, the project ensures that critical data is recovered even if the physical probe is lost to the storm.

Technical Deep-Dive

• LoRa Spread Spectrum Telemetry (RYLR890):
  • The PHY Layer: The Reyax RYLR890 module uses Chirp Spread Spectrum (CSS) modulation. This allows the signal to be decoded even when the signal-to-noise ratio (SNR) is as low as -20dB, which is essential when transmitting through heavy rain, hail, and high-velocity wind associated with supercell storms.
  • AT Command Logic: The modules are configured via a serial UART interface. By setting distinct ADDRESS and NETWORK_ID parameters, the rocket probe and ground station establish a dedicated point-to-point link that ignores interference from other 915MHz devices.
• Geospatial Tracking (NMEA Parsing):
  • The rocket uses the Adafruit Ultimate GPS, which communicates via the NMEA 0183 protocol. The firmware utilizes the TinyGPS++ library to asynchronously parse $GPRMC and $GPGGA sentences, extracting precise Latitude, Longitude, and GPS Altitude (Mean Sea Level) at a 5Hz update frequency.
• Atmospheric Pressure vs. Altitude:
  • The MPL3115A2 is a specialized altimeter with a 20-bit ADC. It calculates altitude based on the Hypsometric Equation, correlating the local pressure to a pre-defined "Sea Level Pressure" ($1013.25$ hPa). This provides a secondary, high-resolution altitude check to verify the GPS data during high-G launches.
• Sensor Fusion & Redundancy:
  • Dual Logging: Data is simultaneously written to an on-board Industrial SLC MicroSD (vibration resistant) and sent via LoRa to a ground-based laptop. If the rocket is destroyed or carried out of range, the ground station maintains the flight profile until the moment of signal loss.
• I2C Bus Contention Management:
  • Both the SHT31 and the MPL3115A2 share the I2C bus (SDA/SCL). The Arduino Nano Every serves as the bus master, polling each sensor sequentially to prevent collision and ensure that timing-sensitive telemetry packets are sent at consistent intervals.

Engineering & Ballistics

• Rocket Modification: The Estes Loadstar II features a payload bay that has been modified for aerodynamic stability. The LoRa and GPS antennas are mounted in the Nose Cone (farthest from the metal-clad sensors) to minimize RF interference and maximize the "Sky View" for satellite acquisition.
• High-G Wiring Strategy: Rapid acceleration and aerodynamic buffeting can cause solder joints to fail. The project utilizes parallel lead-wire junctions and tinned wrapping wire, secured with heat-set tape, to ensure that the electrical bus remains intact under the extreme vibration of solid-fuel ignition.
• Environmental Sampling: To ensure the SHT31 captures accurate ambient data, the clear payload tube must feature micro-perforations. This allows for natural air exchange without compromising the structural integrity of the rocket fuselage.
• Power Distribution: A 9V battery provides a raw source for the Nano Every's VIN pin. The board's internal 5V regulator provides clean power to the sensors, while the 3.3V rail is reserved exclusively for the LoRa transceiver to prevent voltage sags during high-power transmission bursts.

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Contribute to the world of severe weather research with a ruggedized, long-range telemetry probe—built by storm chasers, for storm chasers.