Solar-Powered GPS Tracker: France to Turkey Journey

The Journey

We launched a high-altitude balloon from France that traveled 2,847 kilometers before landing in Turkey. The flight lasted 55 hours and 10 minutes (2 days and 7 hours). The payload transmitted GPS coordinates via LoRaWAN, powered entirely by solar charging with supercapacitor storage.

Hardware: Heltec HTCC-AB02S CubeCell

Why this board: The HTCC-AB02S integrates everything needed for a GPS tracker in one compact package: ASR6052 chip (ARM Cortex M0+ plus SX1262 LoRa radio), built-in GPS module, and onboard solar charging system.

Weight optimization: We desoldered the 0.96-inch OLED display. It's useless on a balloon 7.7km up, and removing it saved precious grams. Every gram matters for altitude and flight duration.

Technical specifications: The ASR6052 combines the MCU and LoRa radio into a single chip, reducing component count and power consumption. The built-in GPS module (AIR530Z variant) eliminates external wiring complexity. The onboard solar charging circuit accepts 5.5-7V panels directly, simplifying power system integration. Deep sleep current draws only 21µA—critical for maximizing flight duration when solar input is limited. Operating on 868MHz LoRaWAN (EU frequency), the compact form factor fits balloon payload constraints without sacrificing functionality.

Why Solar Power with Supercapacitors

At altitude, temperatures drop significantly. The balloon reached 7,768 meters where temperature hit -29.3°C. The payload experienced temperature extremes from -29.3°C at altitude to +40.3°C at ground level. Lithium batteries struggle across this temperature range - internal resistance increases at cold, capacity degrades at heat.

Supercapacitors work from -40°C to +70°C without degradation. Charge/discharge cycles are unlimited. Combined with solar charging, they provided continuous power through the entire 55-hour journey.

The 3W panel generated enough current even through thin clouds to keep supercapacitors charged during day/night cycles.

What Worked

Power System

The HTCC-AB02S's onboard solar charging circuit plus external supercapacitors worked perfectly. Voltage never dropped below 6.8V even during the longest night (14 hours at high latitude).

Solar panel pulled 180-240mA during peak sun - more than enough to offset the GPS + LoRa transmitter draw. During night periods, supercapacitors provided storage without the temperature limitations batteries have at -29.3°C.

LoRaWAN Coverage

SF12 (maximum range spreading factor) with 14dBm transmit power. Coverage exceeded expectations: the balloon reached 7,768 meters altitude while maintaining communication. Across the entire 55-hour flight, 3,309 packets were successfully received by thousands of Helium hotspots scattered across the path. The maximum distance to a receiving hotspot reached 511 km—extreme range enabled by the altitude advantage and clear line-of-sight. Mean travel speed held steady at 50 km/h as the balloon drifted eastward.

The Helium network's extensive coverage meant the balloon was continuously tracked as it drifted across borders. High-altitude LoRaWAN testing is rare—this flight provided real-world data showing extreme range capabilities (511 km!) and how many gateways can receive a single moving device.

Telemetry Data

The payload logged comprehensive sensor data throughout the flight. GPS position tracked the balloon's path across 2,847 km. External temperature sensors recorded extreme swings—plummeting to -29.3°C at maximum altitude (7,768m) and soaring to +40.3°C at ground level, a total temperature range of 69.6°C. Barometric pressure measurements dropped from 1013 hPa at launch to 388 hPa at peak altitude. Each transmission included supercapacitor voltage and solar current readings, providing real-time power system health monitoring. GPS fix quality and satellite count verified positioning accuracy. Mean travel speed across the journey held at 50 km/h. In total, 3,309 packets were successfully transmitted and received by the Helium network.

How Helium Network Enabled This Flight

The Helium network's distributed infrastructure made continuous tracking across 2,847 km possible. Thousands of hotspots received the 3,309 transmitted packets during the 55-hour journey - far more coverage than any single organization could deploy.

Extreme range achieved: The maximum distance to a receiving hotspot reached 511 km—a testament to high-altitude LoRaWAN capabilities. A single packet reached 852 hotspots simultaneously, demonstrating the network density across Europe. The altitude advantage at 7,768m provided unobstructed line-of-sight, enabling these extreme ranges impossible from ground-level transmissions.

Why Helium worked: Community-operated gateways provided coverage in rural areas where commercial networks don't exist. No roaming fees or border crossing issues—one unified LoRaWAN network spanning multiple countries seamlessly. Hotspot owners actively participated in tracking, fascinated by receiving packets from a balloon at 7,768m altitude.

Network effect: At 50 km/h average speed, dozens to hundreds of hotspots received each packet, creating massive redundancy. If one gateway missed a transmission, countless others captured it. This redundancy ensured no gaps in the tracking data despite the balloon's continuous movement.

Public tracking: Helium's blockchain recorded every packet reception, creating a public, verifiable trail of the balloon's path. Anyone could see which hotspots received packets and when, enabling real-time community tracking without centralized infrastructure. The transparency turned a private experiment into a community event.

Community Response

Flight path data got shared across LoRaWAN communities in 4 countries. Turkish LoRa enthusiasts tracked the landing and helped with recovery coordination. The Helium network's open data meant multiple people could follow the journey in real-time, increasing chances of successful recovery.

Complete Hardware List

Main board: The Heltec HTCC-AB02S CubeCell GPS-6502 (868MHz variant) served as the core platform. We desoldered the OLED screen for weight reduction, keeping only essential components. The ASR6052 chip combines ARM Cortex M0+ processor with SX1262 LoRa radio in a single package. The integrated GPS module eliminates external wiring complexity.

Power system: A 3W 6V polycrystalline solar panel captured energy throughout the flight. Supercapacitors (rated -40°C to +70°C) provided energy storage that survived the extreme temperature swings. The HTCC-AB02S's onboard solar charging circuit managed power distribution without additional components.

Antenna: We used a custom 868MHz antenna design sourced from Aliexpress, then tuned it with a NanoVNA for optimal impedance match. Proper antenna tuning maximizes transmission efficiency—critical when every milliwatt counts during night periods.

LoRaWAN settings: SF12, BW125, CR4/5—the maximum range configuration. Operating on 868MHz EU band, these settings prioritize range over data rate, perfect for infrequent position updates from a slowly-moving balloon.

Lessons Learned

What worked better than expected:

Supercapacitors handled the brutal temperature swings—from -29.3°C to +40.3°C (69.6°C range)—without degradation. Solar charging maintained power even through clouds, never letting voltage drop dangerously low. LoRaWAN range reached extremes: 511 km maximum distance to a receiving hotspot. Thousands of Helium hotspots provided continuous coverage across the entire 2,847 km journey, successfully receiving all 3,309 transmitted packets. The HTCC-AB02S's integration simplified the design dramatically—no separate GPS wiring, no external charging circuits, just clean connections. Desoldering the screen proved worth the effort, saving grams that contributed to peak altitude.

What this proved:

Solar power combined with supercapacitors and LoRaWAN handles conditions that challenge cellular or satellite trackers. Temperature extremes from -29.3°C to +40.3°C (69.6°C swing) at 7,768m altitude. 55 hours continuous operation covering 2,847 km. Mean speed 50 km/h. 3,309 packets transmitted and received. Maximum range 511 km. Total hardware cost: under €50.

The Helium network's distributed coverage made this possible—thousands of hotspots provided redundant tracking across international borders. No single organization could deploy equivalent infrastructure.

The HTCC-AB02S is designed for exactly this kind of application. Integrated GPS, LoRa radio, and solar charging eliminate wiring and reduce failure points. Desoldering unnecessary components (the display) optimizes the board for specific use cases where weight matters more than features.