The USB/STDN waveform (Unified S-Band/Spaceflight Tracking and Data Network) has been used to provide telemetry, tracking, and command (TT&C) services for many satellites in addition to NASA near-Earth orbital missions. The tracking and command signals are used in the forward link, or the uplink (Earth-to-space), while the spacecraft tracking and telemetry signals are used in the return link, or the downlink (space-to-Earth). An uplink with a square-wave PRN ranging (pseudorandom noise) or tone-ranging signal is used to improve the carrier acquisition, and ranging performance. Typically the downlink signal is a heavily filtered signal that is needed to reject the side lobes or harmonics of the square waves to satisfy the NTIA (National Telecommunications and Information Administration, a part of US Department of Commerce) emission spectrum requirements. This filtered downlink signal, sometimes called "sine-wave," intentionally reduces adjacent channel interference (ACI) at Earth station receivers. In these space links, it is very important to analyze the modulation losses that affect the TT&C link performance. Currently available analyses assume an unfiltered forward link signal (uplink or Earth-to-space link), and a heavily filtered return link (downlink or space-to-Earth link). In this paper the modulation losses applicable to the USB/ STDN signal with and without spectral filtering are derived for both the forward link (FWD) and the return link (RTN).
Telemetry, Tracking, and Command Link Performance Using the USB/STDN Waveform
2007-03-01
375185 byte
Aufsatz (Konferenz)
Elektronische Ressource
Englisch
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