Remote Sensing Using Micro Satellite Transceivers, 16-R8009

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Principal Investigators
Thomas H. Jaeckle
Helene E. Webb

Inclusive Dates:  12/08/08 – 03/08/09

Background - The purpose of this project was to determine if a new satellite communication service provided by Service Argos offers a capability that could be considered disruptive to SwRI-designed sensors that use satellites to communicate data. The results of this effort provided crucial information to enable SwRI to decide in which direction to proceed for future satellite tracking beacon technologies. This new service was compared to the Iridium Short Burst Data Satellite System, a competing satellite data service.

Approach - SwRI has experience with the previous generations of Argos services, which use one-way devices to communicate data from a sensor, through a satellite, and to a ground station from which a user accesses the sensor data. However, the legacy Argos one-way service has significant limitations. With the launch of its latest satellite payload, Argos activated the new Argos-3 service, which claims to offer two-way communication, a satellite-in-view signal, message acknowledgement and a higher data rate mode. A competing communication system is Iridium, which is a constellation of low-Earth orbit (LEO) satellites that provide continuous worldwide coverage. Iridium offers a variant of the short messaging system (STS) used in cell phones called short burst data (SBD). Iridium, as SwRI learned through this project, offers several important benefits over the legacy Argos service. The disadvantage of Iridium is that SwRI cannot build custom transceivers because of licensing and commercial agreement limitations. This project compared key performance aspects of the Argos-3 and Iridium systems. This project systematically investigated the trade space between battery energy required to complete a communication transaction for various message lengths. The energy per bit of data transmitted and communication reliability were measured for both systems.

Accomplishments - A great deal of data was collected by comparing the performance of each system in passing numerous messages of various lengths. It was hoped that the new Argos service would provide a much more energy-efficient means of collecting data from remote sensors. However, except for very short messages, that was not the case. Additionally, several substantial difficulties using the Argos service were discovered. The conclusion was that the new Argos service was not a disruptive technology and that the disadvantages of that system will drive future developments to use the Iridium SBD technology.

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