For the Firecat proposal/mission, we have shifted our focus from LIDAR to passive infrared sensing. An active sensor generates its own light, and a passive sensor just receives light. A quick calculation indicates that there is a large amount of light due to solar glinting available to the lunar sensor and module. Here is some background info on infrared light
Infrared light is radiated by a candle which we can “feel” with our hands as heat. Here is an image of a candle flame in the infrared:
Space debris around the Earth is exposed to direct sunlight, which contains infrared radiation. Some of this radiation is absorbed by dust and debris, and some of it is reflected. Our team has experience in design and implementation of infrared telescopes and sensors from our work in the aerospace industry.
From the infrared standpoint, it is very helpful to characterize the parts of the fire which are radiating differently. This way we know how to interpret the image generated by our detector. The picture above shows that the outer flame is much hotter than the inner flame, and the melted wax also generates a heat signature. Likewise, we would like to understand and model how different parts of space debris radiate in the infrared part of the spectrum. This is called “phenomenology”, and involves physics and electromagnetic.