Section 1215.102 - Definitions(a)User. Any non-U.S. Government representative or entity that enters into an agreement with NASA to use TDRSS services.(b)TDRSS. TDRSS, including Tracking and Data Relay Satellites (TDRS), WSC, GRGT, and the necessary TDRSS operational areas, interface devices, and NASA communication circuits that unify the above into a functioning system. It specifically excludes the user ground system/TDRSS interface.(c)Bit stream. The electronic signals acquired by TDRSS from the user craft or the user-generated input commands for transmission to the user craft.(d)Scheduling service period. One scheduled contact utilizing a single TDRS, whereby the user, by requesting service, is allotted a block of time for operations between the user satellite and TDRSS. 77 FR 6952 , Feb. 10, 2012