Self-recording oceanographic and meteorological installations in remote areas cannot generally be checked for correct operation, except during routine service visits. In an effort to increase both the time between service visits and reduce the risk of undetected equipment failure or malfunction, a systems utilizing the ARGOS data transmission service has recently been implemented for a recording installation in North Africa. This chapter describes the use of "Service ARGOS" in providing daily control data for wave, tide and meteorological recording systems.
The chapter describes the operational aspects of the survey and satellite systems, together with a brief analysis of the cost implications of using the ARGOS service.
Self-recording oceanographic and meteorological installation in remote areas cannot generally be checked for correct operation, except during routine service visits. These visits may be at intervals of several weeks or months depending upon the site location, local logistics and client requirements.
This chapter presents an example of a recently commissioned system for daily monitoring of a remote installation using the ARGOS system. The installation comprised several oceanographic and meteorological sensors at two sites in North Africa. Local logistics required that the system be capable of continuous operation with a minimum of on-site maintenance. This requirement was solved by the implementation of microcomputer controlled processing, recording and data transmission via the ARGOS system.
The following presents a brief summary of the ARGOS satellite system, and a description of the recording installation deployed in the field. The chapter concludes with a discussion of the operational experiences with the ARGOS system, and the relative cost benefit provided by its use.
ARGOS utilizes the TIROS-N NOAA meteorological satellite and is the result of joint venture between the Central National d'Etudes Spatiales (CNES, France), the National Aeronautics and Space Administration (NASA, USA) and the national Oceanic and Atmospheric Administration (NOAA, USA) the AROGS systems comprises:
fixed or mobile platforms (i.e. boats, buoys, balloons etc.) fitted with Platform Terminal Transmitters (PTTs);
two TIROS-N satellites;
a ground telemetry acquisition and processing network;
a data distribution system.
The TIROS-N satellites have the following orbit characteristics:
circular orbit configuration;
satellite altitude; 830 km (±18 km) and 870 km (±18 km);
orbital period : approximately 101 minutes;
number of orbits per day: approximately 14 for each satellite.
Each satellite crosses the equatorial plane at a fixed time each day. Consequently any PTT comes within a satellite's visibility at the same local solar time each day. Table 1 shows the frequency of passes for various latitudes. The figures apply for both satellites. The mean duration for a pass is about 10 minutes, while that of a zenith pass is 13 minutes.
The ARGOS system can accommodate PTT transmissions to provide geographic location and/or sensor data.
The PTT unit operates on a nominal frequency of 410.64 MHz.