Telemetry and Data Transmission
Data at SNOTEL, Snolite, and SCAN sites are collected and stored by a datalogger installed in the equipment shelter or enclosure. Depending on the location of the site, data are transmitted back to the Water and Climate Information System using one of the following telemetry systems.
Most of the SNOTEL network uses meteor burst communication technology to send and receive data in near real-time. Each SNOTEL site transmits a radio signal into the sky, and this signal bounces off a band of ionized meteorites existing about 50 to 80 miles above the earth. This technique allows communication to take place between remote sites and a master station up to 1200 miles away.
At the master station, the remote site data are checked for completeness. If complete, an acknowledgment message, returning over the same path, tells the remote site not to transmit again during this polling period. The entire process takes less than a tenth of a second.
Meteor burst communication system
In a cellular network, signals carrying voice, text, and digital data are transmitted via radio waves through a global network of transmitters and receivers. Signals are distributed over land through cells, where each cell includes a fixed location transceiver known as a base station.
The Soil/Climate Analysis Network (SCAN) uses cellular data transmission for many sites, especially in the eastern U.S. Cellular modems installed in the electronics enclosure transmit data back to the Water and Climate Information System database.
The Geostationary Operational Environmental Satellite (GOES) system is operated by the U.S. National Environmental Satellite, Data, and Information Service. The system supports weather forecasting, severe storm tracking, and meteorology research. The system is currently composed of two geostationary satellites, GOES-East and GOES-West. SNOTEL, Snolite, and SCAN sites with GOES transmitters send data to the GOES-West satellite, where they are then transmitted back to a receiver station. Once received, the data are converted to meteor burst format and incorporated into the Water and Climate Information System.
Similar to the GOES system, the Iridium Satellite System consists of a network of 66 cross-linked satellites, which operate in near-circular low-Earth orbits (LEOs) about 480 miles (772 kilometers) above the Earth’s surface. Each satellite can project 48 spot beams on the Earth’s surface, and the satellites are cross-linked so that each satellite can “talk” with other nearby satellites.
Much like a cellular network where data are transmitted via multiple cellular towers, the Iridium Satellite System data are relayed from satellite to satellite until they are downlinked at an Iridium gateway and then transmitted to the Water and Climate Information System database.
Iridium Satellite System