User service shall be scheduled only by NASA. TDRSS services will be provided in accordance with operational priorities established by the NASA Administrator or his/her designee. See Appendix A for a description of a typical user activity timeline.

Schedule conflict will be resolved in general by application of principles of priority to user service requirements. Services shall be provided either as normally scheduled service or as emergency service. Priorities will be different for emergency service than for normal services.

Normally scheduled service is service which is planned and ordered under normal operational conditions and is subject to schedule conflict resolution under normal service priorities. Requests for normally scheduled service must be received by the schedulers at the GSFC WSC Data Services Management Center (DSMC) no later than 21 days prior to the requested support time.

At times, emergency service requirements will override normal schedule priority. Under emergency service conditions, disruptions to scheduled service will occur.

The DSMC reserves the sole right to schedule, reschedule, or cancel TDRSS service.

NASA schedulers will exercise judgment and endeavor to see that lower-priority users are not excluded from a substantial portion of their contracted-for service due to the requirements of higher-priority users.

General user service requirements, which will be used for preliminary planning and mission modeling, should include all pertinent information necessary for NASA to determine if the proposed service is achievable. Contact NIMO to discuss usage and requirements.

Such user service requirements information typically includes:

Date of service initiation.

The type of TDRSS services desired (e.g., multiple access, tracking, etc.), and the frequency and duration of each service.

Orbit or trajectory parameters and tracking data requirements.

Spacecraft events significant to tracking, telemetry or command requirements.

Communications systems specifics, including location of antennas and other related information dealing with user tracking, command, and data systems.

Special test requirements, data flows, and simulations, etc.

Identification of terrestrial data transport requirements, interface points, and delivery locations, including latency and line loss recovery.

To provide for effective planning, reference Appendix A, Typical New User Activity Timeline.