THE USE OF TRANSLATORS WITH GPS

Abstract

A method for determining position and velocity as a function of time is required in order to test many systems involving moving platforms, such as missiles or sonobuoys. The Air Force Global Positioning System (GPS) is ideally suited for providing this information. Limitations exist, however, in currently available receivers. They are expensive to use in expendable platforms, plus they require more volume and power than are typically available. An alternative is to use either a translator or a transdigitizer in the vehicle under test. The signals transmitted by the GPS satellites are received by antennas on the missile, translated to a frequency in the telemetry band, amplified, and transmitted to a receiving station. In addition, if a transdigitizer is used, the signal is digitized prior to transmission. Specially designed receiving equipment on the ground processes the transmissions from the translator/transdigitizer, tracks the transmissions from each satellite, and makes the measurements necessary to allow the computation of the platform position and velocity. These systems concepts will be discussed, and a system currently using a translator in a missile and a system using a transdigitizer in a sonobuoy will be described in detail.