Characteristics of the LIBRA NANOMETRICS Tsunami Sensor Network

Characteristics of the LIBRA NANOMETRICS Tsunami Sensor Network

By: Ir S Poniman, M.Si

Tsunami is the result of earthquakes that occur on the seabed and tsunami waves move at a speed of 900 km per hour. Seismo is a vibration sensor is used to detect earthquakes and vibrations on the ground surface.

Libra the nanometric network is a seismic network owned by InaTEWS (Indonesia Tsunami Early Warning System), to provide information services for community-related to weather, climate earthquakes, and tsunami. LIBRA InaTEWS network has 110 remote stations and 1 central recording facility (CRF) or Hub and 1 CRF backup. Each remote station has several main components namely: Sensor, Digitizer, Power System, Modem, Satellite Antenna, and GPS Antenna.

The system works begins with the transmission of signals by the LIBRA Nanometrics satellite to the VSAT antenna, captured by the VSAT antenna and then forwarded to the modem to be modulated and then forwarded to the acquisition of the server for data storage and processing.

Modems on the CRF and remote station are configured, monitored and their maintenance reviewed from a Web modem client via a TCP / IP connection.

The Nanometric modem used is a Cygnus modem that is specifically designed for outdoor and integrates all hardware to receive data from two serial ports then sends it to the CRF or hub via satellite links. In Cygnus, there are integrated parts which include GPS timing with high precision, two serial data input ports, an ethernet port for external access, a satellite modem for inbound and outbound link satellite processes, and all devices needed for interconnection and operation from the process.

The VSAT network is divided into two main lines, namely the hub station and the remote host. Hub station serves to manage all network configurations and monitor all remote stations. The CRF remote station is the central control system, data collector and processor which has the most central role in controlling the entire system.

          Multiplexing Network Data on the LIBRA Network takes data from many remote stations through one satellite channel and uses the same channel to send messages from the CRF or Hub to the remote station. The method used in the multiplexing process is called Time Division Multiple Access (TDMA). In TDMA network systems, each station has a function to send data within a predetermined timeframe or called "slots where the combination of slots for one transmission process per station is called" frame, and has a repetitive cycle, allowing each station the opportunity to send a series of data every few seconds. TDMA frames will change only when new sites are added to the network or when sites are reconfigured.