Passive Millimeter-Wave Spectrometer for Remote Chemical Detection

Transcript

Welcome to a demonstration of the Passive Millimeter-Wave Spectrometer for Remote Chemical Detection. The ultimate goal of the project was to detect a hot target gas in front of a cooler background.

This setup was eventually tested at the Nevada Test Site. Prior to field test we tested the concept in a laboratory. We simulated the field conditions by simultaneously reducing the two relative temperatures. In this demonstration we will show a room temperature gas (CH3CN) with a cold background (liquid nitrogen).

To understand the experiment we will be showing, the first subplot here represents all data channels plotted on a single plot, the second plot represents a two-dimensional representation of the same data, the X axis represents time, the Y axis represents frequency. As the plot is animated later the first and second subplots will have a cross section marker sweep across them.

Finally the third subplot has the current cross section as displayed by the cross section marker on the previous two subplots. In order to obtain usable spectral data, all channels are normalized between a hot load and a cold load.

As the video plays note the difference between a broadband heat source, in this case a human hand, and the spectral response of the target gas. In the case of the heat source the signal registers a difference equally across all frequencies. In the case of the gas note that the response is specific to certain frequencies.