The STX3 module is used in devices from the LinkStar-TRK satellite radio system to SPOT locators used on the ground providing global beaconing services for a range of systems and applications such as cubesats, aircraft, ships at sea, and pipeline monitoring systems to name a few. For cubesats and small satellites the STX3 and the STX3 based LinkStar-TRK provides an invaluable low cost global data communications system. However a key drawback is the module only provides one-way “simplex” communications–there is not a mechanism to send messages and commands globally up to the satellite via the STX3 module. Per FCC regulations and NASA Policy Directive (NPD) 2570.5E “all spacecraft shall be equipped with mechanisms to remotely cease EM emissions unless there is a human presence with this direct capability” – thus satellite operators of STX3 based radios must provide a second radio, an uplink, to cease emissions of the STX3 module. The STX3 module becomes dependent on the functionality of another radio which defeats the global communications capability. As a result, sci_Zone in partnership with Globalstar has begun research and development of the STX4 based radio system – the LinkStar-TRK-X, an adaptation of Globalstar’s Spot-X radio providing low bandwidth global duplex communications that fits within 0.25U of a cubesat (100x100x25mm). The architecture is designed to interface with the cubesat bus, is a PC104 format board, and provides full message downlink and command/message uplink services for the cubesat and small satellite. Over 90% Earth coverage is provided by the LinkStar-TRK-X radio system. The LinkStar-TRK-X design provides support for I2C and an I2C multiplexer, Space Wire, serial connections, USB, and a range of switched and unswitched power connectors to power the LinkStar-TRK-X and supported instruments. The integrated flight computer hosts the QuickSAT/VMS system providing vehicle control, communications, and instrument management functions. QuickSAT/VMS provides a web based interface for easy vehicle configuration, system testing, and management. In this presentation we will present the system design and implementation, and how LinkStar-TRK-X fits within a cubesat architecture, plus how the unit communicates with the desktop and iPhone from anywhere in orbit
