Measured physical characteristics of the West Ford belt

A measurements program has been under way since the dispensing of the West Ford belt. It has been important to estimate belt orbit parameters over an extended period of time, to study dispersion of the belt with time, to determine the variation of dipole density along the orbit with time, and to estimate the total number of dipoles in orbit. Three distinct kinds of experiments have been employed in the measurements program: monostatic radar experiments, bistatic path loss experiments, and bistatic experiments to determine Doppler dispersion. Several estimates have been made of belt orbit parameters; an estimate of mean dipole period, averaged over the first 80 days of the belt life, was found to be 166.455 minutes. Belt physical cross-section dimensions have been obtained at a number of different points on the orbit and over an extended period of time; near the semilatus rectum point on the orbit, 30 days after ejection, the horizontal and vertical belt dimensions were approximately 11×14 km as compared with 17×32 km 200 days after ejection. Experimental estimates of the number of dipoles in orbit indicated that between 16 and 39 per cent of the ejected dipoles were properly dispensed. Measured variation of dipole density along the orbit clearly showed the anticipated initial dense region near the dispenser and the increasing uniformity of dipole density along the orbit with time.