Commercial Ku-Band SATCOM On-The-Move Using a Hybrid Tracking Scheme

The US Army has an unfulfilled requirement to provide long range communications to lower echelon Tactical Operations Centers (TOCs) On-The-Move (OTM). Currently, the Battalion (BN)-Level TOCs can communicate only by terrestrial radios, which are severely range-limited. This MITRE Mission Oriented Investigation and Experimentation (MOIE) calls for the design and prototyping of an affordable satellite communications (SATCOM) terminal that can support reduced data rate SATCOM OTM (SOTM) and Medium Data Rate (MDR) SATCOM On-The-Pause (SOTP) communications. Extended range communications by means of small aperture, low cost satellite terminals is anticipated to be greatly valued by the Army's digitization transformation. The platform stabilization subsystem is a key component of this MITRE program.

We propose a new hybrid-tracking scheme for antenna stabilization for Line-of-Sight (LOS) communications to a commercial satellite operating at Ku-band. Harsh terminal platform dynamic conditions while communicating with the satellite necessitate the use of tracking antennas and stabilized platform pedestals. The tracking system will be a hybrid design, which includes open loop tracking with periodic closed loop updates to correct for drifting of the inertial system. It combines the use of Fiber Optic Gyroscopic (FOGs) sensors with RF-based conical gimbal/step scan feedback. While the gyros compensate for the fast vehicle motion, the lower bandwidth RF tracking loop corrects for the low rate/DC drift errors associated with the ephemeris and gyrosensors. The novelty in our dual loop approach consists of combining these two tracking loops to minimize the tracking scan-loss.

The highly desired low-cost aspect of our platform stabilization design is credited to the use of FOG sensors as a key part of the tracking system. The hybrid design relies heavily on the use of high quality FOGs to track in a "Selective-Open loop (RF-wise) Pointing mode".