Laser Vibrometer-Based Sensor for PPB Level Trace Gas Detection

NASA Langley Research Center researchers are attempting to develop a carbon dioxide detection sensor, one of several proposed science instruments for the Active Sensing of Carbon Dioxide Emissions over Nights, Days and Seasons (ASCENDS) mission. Narasimha Prasad, aerospace technologist at Langley, describes the technology's progression.

Transcript

00:00:10 I was working with a company and they had a new material composition, and we developed what is called a a Photo EMF detector, a highly sensitive detector that can be used for sensing vibrations. This detector can detect pico joules of power and energy. And also it only senses the motion. So when you translate into vibrometer we are able to detect what is phemtometer class vibrations. We first wanted to use this sensor for monitoring the life signatures and also the functioning of the heart of astronauts in a closed environment. And with the CIF funding and we went on to apply the technology for ambient CO2 sensing the Ascends Mission, or such missions. I was the PI on an ascends instrument incubator program where we had proposed to develop an

00:01:02 instrument to fly on global hawk and for the lab measurement we needed an in-situ sensor. Basically the laser vibrometer is an interferometric set up which includes a high repetition grade laser coupled to a photo emf detector. What we do is select a laser that will tune to the resonance band of a given molecule, say CO2, and when the light interacts with the resonance bands, acoustic signatures are produced. They are the tiny vibrations, and these vibrations are now impinged upon a diaphragm, a very thin diaphragm and that way we detect the vibrations, and in an interferometric set up we are able to monitor that. This is novel because sensitivity is parts per billion or below and it's in a very compact

00:01:53 set up and it can be packaged for high altitude measurements. We have made a very proof of concept measurement and we are in the process of developing a package where we will be able to detect the CO2 from ambient environment.