LeoT Autonomous Ground Station
The LEO-T is a small autonomous terminal designed and integrated by AlliedSignal Technical Services for tracking low Earth orbiting spacecraft.
ATSC designed LEO-T to function reliably in a fully autonomous environment. This was accomplished through reliability analysis, the provision of system software utilities to monitor performance, careful selection of hardware, software routines to remove unnecessary files, routines to fine-tune the computer system performance, and a remote reboot capability.
In addition to schedule driven autonomous operations, full remote control capability is provided. In fact, anything an operator can do at the station's Administrative Workstation, an authorized user can do remotely. Autonomous operation can be viewed from varied perspectives.
For example, the Principal Investigator (PI) is interested in the system's degree of user friendliness (how easy it is to operate LEO-T). Similarly, the System Administrator is concerned about the system operating without intervention, except in the event of an anomaly. The System Administrator also relies on the LEO-T status reports and wants to be able to perform diagnostic testing, modify the schedule, and change user priorities. LEO-T autonomy relies on a robust schedule that is modified by remote users and the System Administrator. Spacecraft in the mission set are scheduled for normal operations according to the priority they have been assigned. The station will operate for extended periods of time with no intervention other than periodic scheduling contacts. Schedule execution initiates equipment configuration, including establishing the communications link, and automated testing and pass support activities.
ATSC designed the LeoT system as a prototype for the type of autonomous ground station that can be used as giga-link terminals with the large LEO Systems like Teledesic that will be coming on line after the year 2000. The antenna is an elevation over azimuth with a 7 degree tilt program tracking system housed in a sandwich type radome. The G/T is at least 16.75 dB/K at S-Band and the EIRP is 59 dBm. The present LEO-T supports the 2025 to 2120 MHz uplink band and the 2200 to 2300 MHz receive band with 8 to 8.5 GHz receive available as an accessory. However the LeoT can be modified to function with S-Band and Ku-Band by adding another feed.
The present RF subsystem employs a polarization diversity feed with optimal ratio combining and supports FM, PM, BPSK and QPSK modulation types with up to 15 MBps data rates. The Autonomous Control and Processing subsystem (ACPS) supports CCSDS and TDM telemetry processing with over 9 gigabytes of telemetry data storage capacity. Telemetry data transfer directly to users is performed either real-time or post-pass via FTP/IP or UDP. Real time and "store and forward" spacecraft commanding is provided by the LEO-T. ATSC can modify the telemetry subsystem to handle different modulation types and data rates. Complete telemetry and command simulation capability is available to users pre-pass and via schedule request for LEO-T validation and user systems check out. The LEO-T will autonomously support up to 20 spacecraft with 5 different configuration setups each.
The first LeoT System was deployed in 1998 in Puerto Rico to support the Fuse Mission.
Click here to see ATSC's LeoT Brochure.
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