Ground Segment

The ground segment ensures uninterrupted communications between the customer spacecraft and the customer control center.  The ground terminals provide the hardware and software necessary to ensure uninterrupted communications between the customer spacecraft and the NISN interface to the customer control center.  The SN Project Office, which is located at the NASA GSFC, provides the Project Management and Systems Engineering for WSC/GRGT.

The SN ground segment provides the following functions:

  • Maintains each operational TDRS in a nominal (Ku-Band) mode at all times and ensures that all on-board systems are properly configured and functioning within specified parameters.
  • Transmits forward link traffic to each TDRS for transmission to designated customer spacecraft.
  • Receives and processes customer spacecraft return link traffic from each TDRS, formats and transmits the data to the NISN interface.
  • Monitors state of health and control of the assigned TDRS spacecraft.
  • Measures the range of each assigned TDRS relative to the ground terminal.
  • Measures the closed loop (two-way) range and Doppler or open loop (one-way) Doppler for customer spacecraft, and formats and transmits the measured data to the NISN interface.
  • Simulates customer platform for the purpose of system performance evaluation.

Dedicated Ground Elements:

WSC consists of two ground terminals:

  • Second TDRSS Ground Terminal (STGT)
  • White Sands Ground Terminal (WSGT)

GRS consists of one ground terminal:

  • Guam Remote Ground Terminal (GRGT)

STGT:

STGT

The STGT includes the following subsystems:

  • Three Space-Ground Link Terminals (SGLTs).
  • Three 19-meter Ka-band antennas.
  • One 10-meter S-Band Telemetry, Tracking and Command (STTC).
  • Two dual S/Ku-band 4.5-meter antennas for end-to-end tests.
  • Data Interface System.
  • One TDRS Operations Control Center.

WSGT

WSGT

The WSGT is composed of the following subsystems:

  • Two SGLTs.
  • Three 18.3-meter Ka-Band antennas.
  • One 10-meter S-Band Telemetry, Tracking and Command (STTC) only.
  • Two dual S/Ku-Band 4.5-meter antennas for end-to-end test.
  • Data Interface System.
  • One TDRS Operations Control Center.

Guam Remote Site 

GRGT

The GRS, which is located in Guam at the Naval Computer and Telecommunications Area Master Station (NCTAMS), has one ground terminal, GRGT containing SGLT 6 and SGLT 7.  GRGT closed the Zone Of Exclusion for all the SN customers when it became operational in July 1998.

GRGT is a remotely operated ground terminal that is equipped with two SGLT identical to those at WSGT/STGT.  GRGT supports the TDRS located at 275°W.