Monitoring Space Shuttle Air Quality Using the Jet Propulsion Laboratory Electronic Nose

Abstract

A miniature electronic nose (ENose) has been designed and built at the Jet Propulsion Laboratory (JPL), Pasadena, CA, and was designed to detect, identify, and quantify ten common contaminants and relative humidity changes. The sensing array includes 32 sensing films made from polymer carbon-black composites. Event identification and quantification were done using the Levenberg-Marquart nonlinear least squares method. After successful ground training, this ENose was used in a demonstration experiment aboard STS-95 (October-November, 1998), in which the ENose was operated continuously for six days and recorded the sensors' response to the air in the mid-deck. Air samples were collected daily and analyzed independently after the flight. Changes in shuttle-cabin humidity were detected and quantified by the JPL ENose; neither the ENose nor the air samples detected any of the contaminants on the target list. The device is microgravity insensitive.

Novel Convolution-Based Signal Processing Techniques for an Artificial Olfactory Mucosa

“…Auto-scaling takes the data and scales the magnitude linearly so that all data points lie between 0 and 1, and is signed to preserve the direction of the magnitude (1) Auto-ranging scales the data in a linear manner so that the range of the data is 1. The advantage here is to preserve any swing that may occur in more advanced problems, as multiple odors may cause sensors to respond in both directions (2) These normalized data were passed to the feature extraction stage, along with unmodified raw data for comparison and benchmarking (3)…”

“…Their sensing ability is heavily affected by environmental factors: general drift due to temperature, humidity and background noise, sensor variations and sensor poisoning. These problems, in addition to often wanting to detect very low concentrations (below PPM) of the odor in air [2], [3], make the design of an electronic nose difficult even with expensive autosamplers and the supply of clean air.…”

Sensor systems for the Altair Lunar Lander:

“…The JPL Electronic Nose, now on the ISS JPL eNose has evolved and has flown, in some configurations 6,82 The Third Generation ENose is an air quality monitor designed to operate in the environment of the US Lab on the International Space Station (ISS). It detects a selected group of analytes at target concentrations in the ppm regime at an environmental temperature range of 18 -30 °C, relative humidity from 25 -75% and pressure from 530 to 760 torr.…”

Ground Validation of the Third Generation JPL Electronic Nose

“…The JPL Electronic Nose [1][2][3][4][5] is an event monitor designed and built for near real time air quality monitoring in crew habitat aboard the space shuttle/space station. This is an array-based sensing system which is designed to run continuously and to monitor for the presence of selected chemical species in the air at parts-per-million (ppm) to parts-per-billion (ppb) concentrations.…”

“…In the first phase, a device capable of detecting, analyzing and quantifying ten analytes at the 1-hour Spacecraft Maximum Allowable Concentration (SMAC) was developed. This device was tested successfully in 1998 on Space Shuttle flight STS-95 [4].…”