Tactical Tracking System
This page describes a Tactical Tracking System for high altitude balloons – or any other object – based on the Automatic Position Reporting System (APRS). The term Tactical Tracking here refers to real-time tracking and chasing, where the coordinates of the tracked object are received in real time and sent to a car navigation unit that is able to dynamically update the target coordinates.
The tracking system is based on APRS. Therefore it has many years of heritage and can take advantage of an existing global APRS network. It does not require any R&D since all components are available off-the shelf and even complete turn-key solutions are available.
In addition to position reporting, the system can also transmit telemetry read via analog and/or digital inputs.
The tracking system consists of the following subsystems:
- The transmitter placed on-board the balloon. It transmits GPS coordinates and other telemetry at regular intervals.
- The global APRS network that receives the APRS packets from the balloon via digipeaters and publishes them on the global APRS network, see http://aprs.fi/
- A mobile APRS receiver station that is used for real time tactical navigation in the field where no Internet is available. This station also receives the APRS packets directly from the balloon.
The OpenTracker+ is an open source APRS tracker that receives NMEA data from a GPS receiver, encodes it into APRS packets and generates AFSK signal suitable for audio input to an FM transmitter. It can also transmit telemetry data that is read from the built-in temperature sensor (non-SMT version) as well as the available ADC channels.
OpenTracker+ can be purchased assembled and tested or as a kit. Additionally, there is an SMT version, which is the one we are using. The SMT version does not include a built-in temperature sensor or LEDs.
|Specifications for SMT version|
|Operating modes|| 1200 bps AFSK (RX and TX)|
300 bps AFSK, PSK31 (TX only)
|Supply voltage||DC 6.5 to 28V unregulated or 5V DC regulated|
|Current consumption||8 mA idle, 20 mA transmitting|
|Size||31x18x5 mm (24-pin DIP footprint)|
|GPS interface||NMEA in/out|
|Mechanical interfaces||Pin-header or wire|
|Special features|| * Max 200 mA @ 5 V available for GPS
|1||5VIN||Regulated 5-volt input|
|2||RXD||RS-232 data in (from GPS or computer)|
|3||1WIRE||Dallas 1-wire bus for external sensors|
|4||AOUT||Audio out to radio|
|8||RST||Reset (active low)|
|10||IRQ||Transmit-now, profile select, or counter|
|13||AIN||Audio input from radio|
|16||TXD||RS-232 data out|
|17||RED||Red LED output|
|18||GREEN||Green LED output|
|21||PTT||Push-to-talk signal to radio|
|22||REGOUT||Regulator output - 5 volts|
|24||REGIN||Regulator input - 6.5 to 28 volts|