THE TELEMETRY TEST STATION - AN INTRODUCTION

Abstract

The Telemetry Test Station has been developed at the Digital Systems Division, ISRO Satellite Centre, to test House Keeping Telemetry Packages which will be flown onboard satellites. The main feature of the Test Staion is its configurability, since it is intended to be used with different types of (low bit rate) telemetry packages. Other features include automation of test procedure, and reduction in testing time/increase in repeatability due to minimisation of manual interaction. Since the test station comprises GPIB controlled equipment, hardware and software, thf configurability should be built in at all levels and stages, from design to implementation. Thus since the specification is subject to change, the configuration for structure of the system is traosferred from the designer to the user. This results in a large part of the system being devoted to user interface design, since the computer which is an integral part of the setup must be ‘invisible’ to the user. Due to specialised requirements the user and the system are treated at peer level i.e, at any time during the entire test session, the user can override system process and verify/correct it and equally, the system must also verify/correct user input especially with regard to critical test procedures. The test tession itself (after configuration) is divided into three equally important sections: preprocessing, test and analysis. All the data required during the test run should be made ready before the actual test. Since it has been found by experience that this is not always convenient, the preprocessing software is integrated in to the test session so that the user can perform this at any time. Similarly, the results of the test can also be analysed immediately or even during the test to improve subsequent procedures. This paper describes the prototype telemetry test station which has been built and tested over the past two years. This performance has been satisfactory. The system integration features and design problems and solution are high lighted.