For all but specific PI-driven experiments using some of Flexible Array equipment, all sensor signals digitized and time stamped at the sensor site are continuously transmitted in near real time to the Array Operations Facility.
The advantages of the digital USArray network are:
The most preferable solution is portable VSAT modems. This system is a two-way satellite Internet "always-on" system consisting of a 0.5 m dish and a satellite modem that routes data from remote users through, for example, the GE-4 and Telstar 7 satellites to a downlink hub and then to the Internet. The system is targeted for home users with the expectation of low uplink and high downlink bandwidth requirements and requires an onsite computer and AC power (modem draws 30 W power). Two-way satellite-based Internet service offers download speeds close to those available via cable modem or DSL without the need for phone lines or an Internet Service Provider (ISP). The dish is connected to a satellite modem with a dedicated IP address using standard coaxial cables.
Satellite coverage is provided throughout the conterminous United States and Alaska. Cost is estimated to be $3600 for the dish and modem, and $180/month for continuous operations. As market penetration spreads into the home consumer market, these prices will likely continue to fall.
Advantages of VSAT modems include rapid deployment and demobilization time. Disadvantages include high power consumption (15-20W), and requirements for the dish to have a clear view of the southern sky.
This is a well-established telemetry technology that has been in use in several PASSCAL programs for many years. RF modems are serial radios that provide a digital carrier detect signal to denote a working link. RF links will likely be used in hostile terrain, or to carry the signals to a drop point that provides access to the Internet. While the technology is quite mature, the disadvantages are potentially lengthy deployment times, and higher failure rates than the consumer-based satellite technology. Furthermore, RF modems do not communicate using IP, so the signal must be converted to IP at the drop point.
Local Internet access may be available if the site is located on private property, near buildings, etc. This has the advantages of rapid deployment time, as well as providing power and possible security. However, these are often sites of considerable cultural noise.