Analog Telemetry Research Articles

Tracking and data acquisition for space exploration

The tracking and data acquisition systems provide the key link between the remote spacecraft and the scientific experimenter on the ground. The operation of the space experiment takes place through the links of command, telemetry and tracking. The evolution from the early very simple spacecraft missions toward more complex and sophisticated missions has been paralleled by a similar evolution in the tracking and data acquisition systems. The early Minitrack interferometer tracking system still carries the major tracking workload for space missions; however greater tracking accuracy requirements for more recent missions, such as the Orbiting Geophysical Observatory and the Apollo mission, have brought about the development of unified tracking and data acquisition systems which utilize hybrid pseudo-random code/sidetone ranging techniques. The data acquisition has evolved from analog telemetry systems to the present day heavy use of PCM digital telemetry. Likewise the command systems have evolved from early simple ‘on/off’ command systems into PCM digital command data systems. The trend is toward greater real time control of more complex functions on board the spacecraft. Newer spacecraft are incorporating computer-type systems in the spacecraft which require programming and memory load through the ground command link. The most attractive concept for the next generation network for tracking and data acquisition is a network consisting of synchronous-orbit Tracking and Data Relay Satellites for covering launches and low-orbit earth satellites plus a few selected ground stations for supporting spacecraft in high earth orbit and lunar orbit.

Plasma Electron Detector Using an Open Electron Multiplier

The Triaxial Electron Spectrometer, scheduled for flight on the OGO-E spacecraft, measures flux and energy distributions of electrons reaching the detector with from zero to 10 kilovolts energy. Electrons are analyzed in a curved-plate, electrostatic analyzer, and detected with a windowless continuous-dynode electron multiplier. The multiplier is operated in a constant-output, variablegain, current mode as the null detector in a feedback circuit. Five decades of dynamic range for flux measurements are obtained with a logarithmically compressed analog telemetry signal. Tests of the gain stability of two different channel multipliers have been made for periods of up to 850 hours. These tests indicate that the gain loss can be limited to a factor of two or three during the one year lifetime of the spacecraft.

A Universal Data Processing System for the Mark 1 Aerospace Systems Environmental Chamber

A data processing system, designed specifically to accommodate the vehicle instrumentation test requirements of a large environmental space simulation chamber is described. Prominent features of the system include a versatile input section capable of accepting FM/FM, PCM, PAM/PDM telemetry signals, and analog information; a stored program analog sequencer and telemetry decommutator: a data compressor; and an on-line computer. Primary emphasis in system design has been placed on flexibility and versatility. Reasons for this emphasis are presented with views on system utilization.