THE ELECTRONIC SWITCHING SPHERICAL ARRAY (ESSA) ANTENNA FOR THE EARTH RADIATION BUDGET SPACECRAFT (ERBS)

Abstract

The ESSA is a microprocessor controlled antenna for low orbiting spacecraft for telemetry and command relay through the Tracking and Data Relay Satellite (TDRS) System. The array is a hemispherical shape which is covered with disk radiating elements. A group of radiating elements are continuously selected by the microprocessor controller to form a beam in the direction of a TDRS. A radial switching power divider uses PIN diodes to select the desired radiating elements. The antenna gain is a function of the size of the hemispherical dome. A 30-inch diameter dome is presently being built for the Earth Radiation Budget Spacecraft (ERBS). Gain of this antenna over a hemisphere is 14 dBi and polarization is left hand circular. There are 145 radiating elements with 12 being used at one time to form a beam. The ESSA subsystem weighs 74 pounds and power consumption is 20 watts. R. F. power handling capability is 30 watts. The S-Band radiating elements have a 10 percent bandwidth which allows simultaneous transmission and reception.