Minitrack

The Minitrack Network, was the first U.S. satellite tracking network to become operational, in 1957. It was used to track the flights of Sputnik, Vanguard, Explorer, and other early space efforts. Minitrack was the progenitor of Spacecraft Tracking and Data Acquisition Network (STADAN) and the Manned Space Flight Network (MSFN).

When the proposals for satellites floated in the mid 1950s, the question of tracking them naturally arose. Three approaches were considered:

The optical and radar approaches did not require a cooperative target, but had the major problem of acquisition, or finding the target in the first place, since they had very small fields of view. The NRL proposal needed a transmitter on the target, but could easily measure a target anywhere in a wide field of view. The NRL proposal was accepted and turned into the basis of the Minitrack stations.

From a NASA history document:

In early April 1955, Milton Rosen, John Mengel, and Roger Easton assembled informally at NRL and generated a document entitled, "Proposal for Minimum Trackable Satellite (Minitrack)." No date and no authors are listed on this key report; but, according to Rosen, it preceded only by a few days a more formal report with the title, "A Scientific Satellite Program," April 13, 1955, and written by the NRL Rocket Development Branch. Appendix B of this document was labeled, "The Minitrack System" and was nearly identical to its predecessor of a few days. The name "Minitrack" now appearing for the first time on paper, was coined by John Mengel.

The original proposal had only a single pair of stations. However, this was soon realized to be insufficient. From the NASA history:

Before the end of 1955, ideas changed drastically. First, it was realized that a single pair of stations would provide very limited geographical coverage, rendering data acquisition difficult and the accumulation of orbital data very slow. Four pairs of stations across the southern U.S. were next proposed. The idea of a "radio fence" was implicit in this suggestion; i.e., the creation of a long chain of overlapping antenna patterns that the satellite must intersect frequently. The trouble was that the planned orbital inclination of the Vanguard satellite would keep it away from the southern U.S. too much of the time. The next logical step was the construction of a long north-south fence that the satellite would pass through on almost every orbit. But the Vanguard program could not financially support a long chain of paired stations; besides, further thought soon showed that complete orbital data could be computed from angular (interferometric) tracking alone. These changes in thinking manifested themselves in a report describing a chain of nine single Minitrack stations strewn along the 75th meridian. To the regret of some engineers, ranging and velocity-measuring capabilities were dropped.

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