European OTS satellite transmit antenna patterns

Comprehensive antenna performance measurements on OTS 2 were performed for the first time in October 1978. The method relied on the use of a large number of ground stations, and was supported by spacecraft depointing. The results became available in December 1979, following a substantial coordinated effort of the many co-operating parties. As it is clearly desirable to reduce the allocation of time and effort required to analyse antenna patterns, a revised method was proposed. This new method relies on wide-angle spacecraft depointing and needs support of only one earth station. A test was implemented for the spotbeam antenna pattern, demonstrating that the revised method could perform mapping very efficiently. The revised method is presented in some detail, and results are compared with those obtained from the first test method and with prelaunch predictions. The effect of antenna beam depointing through thermal deformation has been determined to demonstrate the validity of the revised method. The data-processing system has been streamlined so that results can now be obtained in 24 hours following completion of the test, which normally takes about 48 hours.