Communication Satellites (4th Ed.)
Donald Martin
Chapter 1: Experimental Satellites (cont.)
The West Ford concept [1–4] grew out of a 1958 summer study on secure, hard, reliable communications. The conclusions reached were the following:
|
West Ford Dipoles |
- Use satellites and microwave frequencies for long distance communications
- Put all active equipment on the ground for reliability
- Use a belt of dipoles instead of a single satellite for hardness
When the concept was defined openly, there was some adverse reaction because of the uncertain effects on optical and radio astronomy. After some time, the project was allowed to proceed under certain restrictions.
West Ford and Echo were the only two passive communication reflectors put into orbit. Echo could rightly be called a satellite, but the West Ford reflector consisted of 480 million copper dipoles. The length was chosen to correspond to a half wavelength of the 8-GHz transmission frequencies used in the program. Other West Ford details are as follows:
Satellite
480 million copper dipoles, each 0.72 in. long, 7 X 10-4 in. diam
88-lb dispenser plus dipoles; dipoles weighed 43 lb
Frequencies used
7750, 8350 MHz
Orbit
1970-nmi nominal altitude
Nearly circular, nearly polar
Dispersion: 8-nmi cross-orbit, 16 nmi radially, 1300-ft average distance between dipoles
Orbital history
First: launched 21 October 1961, dispenser did not release dipoles
Second: launched 9 May 1963, fully dispersed August 1963
Atlas-Agena B launch vehicle
Management
Developed by MIT Lincoln Laboratory
The dipoles were dispensed from an orbiting container in May 1963. At first, all were concentrated in one portion of the orbit. During the first few weeks, voice and frequency shift keying (FSK) data up to 20 kbps were transmitted from Camp Parks (Pleasanton, California) to Millstone Hill (Westford, Massachusetts—the source of the project name). Four months later, when the belt was fully extended, the density was much lower, and only 100 bps data were transmitted. Because of this low capacity and the increasing performance of active satellites, no further experiments of this type were attempted. The last transmission of signals was accomplished in 1965, and a combination of measurements and analytic predictions indicated that all the dipoles would reenter the atmosphere before the end of the 1960s.
******
- Special Issue on Project West Ford, Proceedings of the IEEE, Vol. 52, No. 5 (May 1964).
- I. I. Shapiro, "Last of the West Ford Dipoles," Science, Vol. 154 (16 December 1966).
- W. W. Ward and F. W. Floyd, "Thirty Years of Research and Development in Space Communications at Lincoln Laboratory," The Lincoln Laboratory Journal, Vol. 2, No. 1 (Spring 1989).
- W. W. Ward and F. W. Floyd, "Thirty Years of Space Communications Research and Development at Lincoln Laboratory," chapter 8 in Beyond the Ionosphere: Fifty Years of Satellite Communication, A. J. Butrica, ed., NASA History Office, Washington, D.C. (1997).
Next: Telstar
