DIGILOCK Telemetry System for the Air Force Special Wreapons Center's Blue Scout, Jr.

Abstract

The Blue Scout, Jr. is a sounding rocket which will be instrumented to measure various forms of radiation at altitudes up to 100,000 miles. Space-General Corporation has built a Digilock telemetry system to convey the radiation information from the vehicle to the earth. The telemetry flight-unit communicates twenty 5-bit digital inputs, encodes the selected words into one of a family of binary orthogonal codes (the particular code selected depending on the value of input data), and phase modulates a transmitter with the selected code sequences. At the ground station the signal is fed to a specially designed phase-lock receiver, which demodulates the phasing information on the received signal and applies the video information (which is binary in the absence of noise) to a tape recorder. The tape is played back at the data-reduction center; the played-back signal is filtered by an integrate-and-dump circuit and then re-recorded on tape in a format suitable for processing by an IBM computer, which, by mechanizing a matched-filter type of decoder, yields the originally transmitted radiation data. Because of the orthogonal nature of the transmitted codes and the method used for modulating and demodulating the r-f carrier, it is possible to achieve a communication efficiency which is unsurpassed by any other existing system. In the present application, the Digilock system conveys information at a rate of approximately 64 bits/sec from a distance of 100,000 miles using only one-quarter watt of transmitted power; the resulting error rate per information bit is considerably less than 10^-6.