Piece of APL history floats in past inaugural parade
Posted on 17. Jan, 2009 by Tracey Reeves in Uncategorized
The APL float passes in front of the reviewing stand. Click for larger view.
It’s not easy to score a spot in a presidential parade, but 48 years ago, Johns Hopkins’ Applied Physics Laboratory did just that. Having developed the Transit Navigation Satellite System for the U.S. Navy, APL was invited to be a part of the Navy’s float in John F. Kennedy’s inaugural parade in 1961.
The Transit program, the first worldwide, all-weather satellite navigation system, was born shortly after the launching of Sputnik 1, on Oct. 4, 1957, when APL scientists William Guier and George Weiffenbach noted a Doppler shift in the satellite’s signals and a difference in signal pattern from one pass to the next. The two researchers concluded that a satellite orbit could be accurately determined by Doppler tracking.
At that point, Frank T. McClure, former deputy director of APL, hypothesized that by knowing a satellite’s orbit, one could deduce where the listening station (ship or ground ) is located. Thus was born the idea of a Doppler navigation system and the Transit Navy Navigation Satellite System.
Transit satellites l-A and l-B were the first two satellites launched to test the Doppler shift’s navigation application. The l-A satellite, launched in 1959, did not achieve orbit. Satellite I-B was successful, travelled 1.1 billion miles in its journey around Earth before its orbit decayed and it burned up in the Earth ’s atmosphere in October 1967.
Several more satellites were tested and refined before the Transit system became operational in 1965. The Navy was able to use the system to not only guide Navy ships, but to also guide commercial, cruise, and sporting vessels of many nations. Over 80,000 Transit navigation receivers have been placed in service over the years. Because of its pinpointing accuracy, Transit became the first worldwide satellite surveying system.
After 30 years of operation, the Transit system has been replaced with the Global Positioning System (GPS), a constellation of satellites developed by the Air Force and now used for ship, aircraft and automobile navigation.
As the folks at APL like to tell it, it’s because of their Transit Navigation Satellite system that people around the world will be able to watch President-elect Barack Obama’s inauguration on Tuesday
Leading up to the Inauguration, Perspectives features a series of reflections on the new U.S. presidency from members of The Johns Hopkins University community. Updated daily.