A computer program autonomously manages the calibration of a quadrupole ion mass spectrometer intended for use in monitoring concentrations and changes in concentrations of organic chemicals in the cabin air of the International Space Station. The instrument parameters calibrated include the voltage on a channel electron multiplier, a discriminator threshold, and an ionizer current. Calibration is achieved by analyzing the mass spectrum obtained while sweeping the parameter ranges in a heuristic procedure, developed by mass-spectrometer experts, that involves detection of changes in signal trends that humans can easily recognize but cannot necessarily be straightforwardly codified in an algorithm.
The procedure includes calculation of signal-to-noise ratios, signal-increase rates, and background-noise-increase rates; finding signal peaks; and identifying peak patterns. The software provides for several recovery-from-error scenarios and error-handling schemes. The software detects trace amounts of contaminant gases in the mass spectrometer and notifies associated command-and-data-handling software to schedule a cleaning. Furthermore, the software autonomously analyzes the mass spectrum to determine whether the parameters of a radio-frequency ramp waveform are set properly so that the peaks of the mass spectrum are at expected locations.
This work was done by Seungwon Lee and Benjamin J. Bornstein of Caltech for NASA’s Jet Propulsion Laboratory. For more information, download the Technical Support Package (free white paper) at www.techbriefs.com/tsp under the Software category.
This software is available for commercial licensing. Please contact Karina Edmonds of the California Institute of Technology at (626) 395-2322. Refer to NPO-45364.
This Brief includes a Technical Support Package (TSP).
Autonomously Calibrating a Quadrupole Mass Spectrometer
(reference NPO-45364) is currently available for download from the TSP library.
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Overview
The document serves as the Interface Control Document (ICD) for the Vehicle Cabin Atmosphere Monitor (VCAM) Autonomous Calibration Software (ACSW), developed to autonomously detect and identify trace organic species in the International Space Station (ISS) cabin air. The VCAM utilizes a quadrupole ion trap mass spectrometer to analyze chemical analytes by applying a quadrupole RF electric field to hyperbolic electrodes, allowing for the determination of mass fractionation patterns. To achieve the necessary mass resolution and dynamic range, the mass spectrometer's parameters must be calibrated.
The calibration process is based on a heuristic procedure that identifies changes in signal trends recognizable by humans but challenging to codify algorithmically. The ACSW was developed through close collaboration with instrument experts, translating this heuristic approach into a software algorithm. The document outlines the protocols and formats for information exchange between the VCAM ACSW and the VCAM Command and Data Handling Flight Software (C&DH FSW), detailing how the C&DH FSW should invoke the ACSW and manage the results returned by its routines.
The ACSW comprises eight high-level analysis functions that directly interface with the C&DH FSW, including functions for initialization, background checking, signal checking, optimization of various parameters, mass calibration, and mass peak checking. Additionally, there are nine Boolean-type analysis decision variables that reflect the outcomes of the calibration analysis functions, indicating whether specific conditions are met (TRUE or FALSE).
The document emphasizes the importance of the VCAM in monitoring air quality aboard the ISS, particularly in the context of chemical events that may alter the concentration of organic species. By providing a robust calibration mechanism, the ACSW enhances the reliability and accuracy of the VCAM's measurements, contributing to the safety and well-being of astronauts in the confined environment of space.
Overall, this ICD not only outlines the technical specifications and operational protocols for the ACSW but also highlights the collaborative efforts involved in developing a sophisticated tool for maintaining air quality in space, showcasing NASA's commitment to advancing technology for human space exploration.
