Spread Spectrum Acquisition and Tracking Performance for Shuttle Communication Links

The spread spectrum acquisition and tracking performance for the Shuttle
S
-band and
Ku
-band communication links are analyzed and compared to test results. The
S
-band link requirements are more severe than those of the
Ku
-band links, hence, different despreader designs were developed for the two systems. The
S
-band despreader acquires pseudonoise code lock by examining all possible code phases in half chip steps while the
Ku
-band despreader acquires pseudonoise code lock by continuously sweeping a tau-jitter loop. Both despreaders employ a tau-jitter loop for code tracking. The code tracking performance is computed for the tau-jitter loop and compared to that of the more complex delay lock loop.