DARTS Advanced Ranging Modem

Digital Advanced Ranging using Transport Stream packets (DARTS) is an innovative method for precise ranging from an earth station to a satellite using the DVB-S transport stream. The system accurately measures the round trip delay between a DVB-S transmitter and a receiver, providing data used to determine the orbit of geostationary spacecraft. DARTS was developed by TechCom engineers, in cooperation with FhG-IIS and ASTRA.

The DARTS ranging system is based on the precise determination of the arrival time of specific ranging packets at the payload uplink and downlink. The full system consists of a ranging packet generator, a ranging receiver at the uplink site, and at least one ranging receiver at a downlink site.

The ranging packet generator inserts ranging packets into the DVB-S transport stream either via a multiplexer or directly into a DVB-S modulator. The round trip delay of the signal on the path between the transmitting satellite and the receive site is determined by subtracting the packet transmission time from the packet reception time.

The DARTS system enables easy implementation of “pseudo” multi-site ranging, through the combination of a single transmitting unit, with several receive-only units geographically dispersed throughout the satellite footprint.

To ensure accuracy and quality, the system and the modem has undergone laboratory tests as well as long-term evaluation including live satellite measurements. The accuracy achieved by pseudo-ranging in the orbit determination is less than one meter in radial direction.