Return Data Delay (RDD) is the delay from generation in the spacecraft to receipt and time tagging on the ground. Knowing the various data delay values allows us to calculate, the time on board the spacecraft to within typically about 30 msec. The use of RDD requires a knowledge of the spacecraft range at the time of interest. Spacecraft delays are measured prior to launch. Ground Station delays are measured initially and typically whenever configuration changes are made to the station. RDD can be used on noncoherent services where USCCS requires the use of coherent services. RDD can be used on GN type spacecraft where USCCS is not an option.
Return data delay (RDD) of a ground station, in this case the Second TDRSS Ground Terminal, is needed by science spacecraft Project Operations Control Center personnel for setting their onboard clock. RDD is the signal delay of the station from the space to ground link antenna's range reference point to the multiplexer/demultiplexer (MDM), where a Universal Time Coordinated time tag is placed on the data stream.
The Return Data Delay Paper provides detailed information regarding the measurement of RDD through the STGT. This activity was undertaken when a timing discrepancy was discovered by TDRSS users who alternated between the WSGT and STGT.
Return Data Delay (Requires Adobe Acrobat Reader)
