Tdrss

S-band K-band Ku-band

S-band K-band Ku-band

QPSK Spread spectrum

QPSK Spread spectrum

Narrow beam

TDRSS User Standard (See NASA Goddard STDN 1012. TDRSS Users' Guide)

Optical

IRto UV

IRto UV

PPM/ PCM

PPM/ PCM

Telescope pencil beam

Frequency depends on device

Legend:

FSK = Frequency Shift Keying PSK = Phase Shift Keying AM = Amplitude Modulation PCM = Pulsed-Code Modulation FM = Frequency Modulation PM = Phase Modulation QPSK = Quadrature Phase Shift Keying PQM = Phase Quadrature

Modulation PPM= Pulse Position Modulation

Table 11-26 contains detailed mass, power, and volume characteristics of three common TT&C subsystems: TDRSS-compatible in the S-band, generic X-band, and typical Ku-band. The information in these two tables comes from specification sheets issued by manufacturers of communication hardware, and summarizes today's technology for TT&C subsystems.

TABLE 11-26. Typical Parameters for TT&C Subsystems. Two transponders provide redundancy and two hemispherical-coverage antennas offer full coverage. The Ku-band system assumes another (S-band) system applies when the spacecraft deviates from its proper attitude. (Courtesy of TRW and L3 Communications)

TABLE 11-26. Typical Parameters for TT&C Subsystems. Two transponders provide redundancy and two hemispherical-coverage antennas offer full coverage. The Ku-band system assumes another (S-band) system applies when the spacecraft deviates from its proper attitude. (Courtesy of TRW and L3 Communications)

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