Tech Briefs

New architecture developed with improved capabilities adds radiation hardness.

A modular architecture has been conceived for the design of radiation-monitoring instruments used aboard spacecraft and in planetary-exploration settings. This architecture reflects lessons learned from experience with prior radiation-monitoring instruments. A prototype instrument that embodies the architecture has been developed as part of the Mars Advanced Radiation Acquisition (MARA) project. The architecture is also applicable on Earth for radiation-monitoring instruments in research of energetic electrically charged particles and instruments monitoring radiation for purposes of safety, military defense, and detection of hidden nuclear devices and materials.

MARA Instrument Phase I Prototype is shown in two-detector configuration. (Note: CEV is Crewed Exploration Vehicle.)

Whereas prior such instruments have contained non-radiation-hardened parts, an instrument according to this architecture is made of radiation-hardened/radiation- tolerant parts, enabling the instrument to resist damage by the radiation that it is intended to measure. One of the building blocks in this modular architecture is a single-channel radiation-detection circuit, which is essentially a detector interface, signal-processing and measurement circuit, dedicated to a single radiation detector that provides radiation-event data to the CPU. The interface between the single- channel radiation-detection circuit and the rest of the instrument is a PC/104 computer-bus interface. [PC/104 is an industry standard for compact, stackable modules that are compatible (in architecture, hardware, and software) with personal- computer data and power-bus circuitry.] Multiple single-channel radiation-detection circuits can be stacked to create a multiple- detector instrument.

The present architecture as embodied in the MARA instrument design offers the following advantages over the architectures and designs of prior radiation-monitoring systems:

The detector interface circuitry in prior instruments included voltage-feedback operational amplifiers, which do not enable accurate tracking of the rising edges of incoming pulses and, as a result, do not enable deterministic discrimination among different levels of radiation events. In contrast, the MARA circuit design provides the capability to more accurately differentiate among different types of energetic charged particles.

Unlike prior designs, the MARA design provides for correlated double sampling, which offers the advantage of subtraction of correlated noise between reset samples and data samples, thereby reducing spurious offsets and the effects of low-frequency noise.

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