Any description of the execution phase of satellite operations must be presented in terms of the kind of program being supported. Thus, the following paragraphs will relate the execution phase to these four kinds of programs: Low altitude, medium/high altitude, ballistics, and ascent only.

3.0.1    Low-Altitude programs

The low-altitude satellites have an orbital period of approximately 90 minutes. Since the SCOFF has seven RTS's, there are usually one or more RTS's that will contact a satellite at some time during each orbital revolution. Each occasion during which an RTS can contact a satellite is referred to as a "pass". Pass durations for the low altitude satellites seldom exceed 400 seconds. Those revolutions during which no contacts are available are referred to as "dead revs". Dead revs usually occur once per day. The low altitude satellites normally require only one pass per revolution support. Support that is provided during the execution phase can be divided into categories of ascent, orbit adjust, pass, recovery, and debits support. Certain passes may include two or more of the categories of support, as seen from the following discussions.

3.0.2    Medium/High-Altitude Programs

Satellites for these programs have orbital periods that exceed 90 minutes - depending on the altitude of their orbits - so that, assuming there are no scheduling problems, the support time available for these satellites is greater than that available for low altitude satellites. Synchronous satellites (at an altitude of approximately 19,300 nautical miles) are continuously in view of one or more stations, and satellites for the Vela, orbiting the earth at an altitude to 60,000 nautical miles, have a period of approximately 4.5 days and can be supported for as much as 18 hours per pass. But unlike low-altitude support that encompasses the total time that the satellite is in view of a station, support (passes) for these programs is scheduled only for portions of available pass times. Passes are scheduled at various times and for various durations (many hours continuously at times) depending on program needs and objectives. Support during the execution phase can be divided into the categories of ascent, orbit adjust, or repositioning (some programs only), and pass support. Debits and recovery are not normally undertaken. Many facets of medium- and high-altitude programs are essentially the same as those of low altitude programs.

3.0.3    Ballistic Vehicle Program

Up to three SCF Tracking stations may be required to support a ballistic operation. The term "ballistic" applies to all types of SCF-supported operations during which an object is not injected into orbit. The type of support provided in similar to that provided for launch and ascent of orbital vehicles, but there are some differences. The most significant difference are that (1) most types of ballistic support involve multiple vehicles, and (2) as many as seven downlink frequencies are involved. Prelaunch support for ballistic operations is similar to support for orbital operations. Launches are conducted from the Western Space and Missiles Center; normally both sides of Vandenberg Tracking Station are used for launch. All ballistic-operations telemetry that is received at SCF tracking stations is recorded; during certain operations telemetry modes are required for some vehicle-to-ground links. Tracking data are necessary to determine the actual trajectories of the objects.