Radiolocation System (RS) belongs to our recent projects. The main purpose of RS is to track flying objects (e.g. sounding rockets, weather balloons) and retrieve them at the end of flight. The RS consists of two terminals: internal – planted inside a rocket (Rocket Terminal – RT) and on the external – the one the ground (Terrestrial Terminal – TT). The terminals communicate within the unlicensed ISM radio frequency of 869 MHz using half-duplex method.
Both terminals are equipped with GPS/GLONASS and Communication & Control modules. The Rocket Terminal includes a power amplifier with +27 dBm (0,5W) output power and an omnidirectional antenna. The main components of the Terrestrial Terminal are a receiver with sensitivity of down to -132dB and a directional antenna.
The block diagram of the system can be seen in the Figure below.
Terminals have high processing power and low energy consumption, a definite advantage for mobile devices powered by batteries. The main functionality of the RS is “radio fox hunting” using a directional antenna (Yagi-Uda) and Received Signal Strength Indication (RSSI). The next functionality is sending localization coordinates from a rocket to the ground terminal.
The sounding rocket mission consists of a few stages, the crucial ones include:
1) A rocket on a launcher and pre-flight checks/preparations
2) The main phase of the rocket flight (rocket accelerated by engine)
3) Inertial flight with an inactive engine
4) Falling with an open parachute
Initially, the Radiolocation System was designed for the use in stages from 3 to 5 for a rocket flight tracking. As the system was developing additional features were added to improve the system usability. Measurement of the rocket’s speed using Doppler radio wave shift in the 2nd stage of the flight was one the improvements.
The system performance was evaluated during ground tests in Tricity area. The first test was an attempt to achieve a maximum distance between the terminals while maintaining a correct communication. In this verification, we obtained a distance of 28,1 km (about -77 dB RSSI), which is most probably still far from the absolute maximum range of the system.
The topographic profile of the test area is presented below.
The second test was an attempt to find the Rocket Terminal in a forest environment. The RT has been moved and hidden in the bushes, then the search based on RSSI level and GPS coordinates was started. The topographic profile of the test area and the routes of both terminals are presented below.
Both tests have shown that system works properly. The Radiolocation System is still in its development phase.