Electronic System for an Impact Mass Spectrometer with High Dynamic Range for the GIOTTO Probe

The measurement objectives of the space probe GIOTTO include the analysis of the dust particles of the comet HALLEY with an impact mass spectrometer of the "time-of-flight" type. The performance of this spectrometer should be comparable to that of commercial laboratory instruments. Nevertheless, size, weight and power consumption must not exceed the stringent limitations caused by the space application. The wide mass range of the dust particles to be analyzed and the short flight times of the ions - caused by the compact mechanical layout of the spectrometer - require a special design for the electronic system. The key features are an automatically event-controlled sensitivity adjustment, which is obtained by an analog multiplexing of the dynode signals of an electron multiplier, and a 3 decades measurement range within a spectrum with a relative error less than 10% which is achieved by a wideband logarithmic amplifier in combination with a flash ADC.