Section 1215.106 - User command and tracking data(a) User command data shall enter TDRSS via the NISN interface at WSC or GRGT.(b) NASA is required to have knowledge of the user satellite orbital elements to sufficient accuracy to permit TDRSS to establish and maintain acquisition. This can be accomplished in two ways: (1) The user can provide the orbital elements in a NASA format to meet TDRSS operational requirements.(2) The user shall ensure that a sufficient quantity of tracking data is received to permit the determination of the user satellite orbital elements. The Flight Dynamics Facility (FDF) at GSFC will provide the orbit determination service to these users. The charges for this service will be negotiated between the FDF and the user and will be dependent on user requirements. 77 FR 6952 , Feb. 10, 2012