From Paul Newman, GloPac co-project scientist:
One of the instruments being flown on the Global Hawk is the Airborne Compact Atmospheric Mapper. ACAM is about the size of a microwave oven, and it is mounted in the bottom of the tail of the Global Hawk.
ACAM has two parts: a spectrometer and a high-definition video camera. We all know about cameras, but what is a spectrometer? It is used to measure light at hundreds of wavelengths (both visible and invisible). Sunlight is composed of many colors that combine to form white light, and each of these colors has a specific wavelength. For example, red has a wavelength of about 650 nanometers (or 650 billionths of a meter), green is about 510 nanometers, and blue is about 475 nanometers. Digital camera images combine the red, green, and blue wavelengths to create photos.
The ACAM spectrometer can see wavelengths from about 300 to 900
nanometers, and can resolve light differences of about 1 nanometer. So what good is that? Well, certain gases absorb certain wavelengths of light, but not others. For example, ozone absorbs very strongly 310 nanometers, but much less at 330 nanometers. This difference allows us to measure how much ozone is below the Global Hawk as we fly along. Hence, we use ACAM to measure things such as pollution and dust in the lower atmosphere.
I also mentioned that ACAM has an HD video camera. The ACAM principal investigator, Scott Janz, pulled the instrument out of the plane’s tail, turned it on its side, and pointed the instrument at the Global Hawk on Thursday morning. He added a little music to show all of the detailed work that is involved in our instrument integration. Of course, he also added me doing a bit of a dance in the video. As you can tell, the coffee on Thursday was over-caffeinated.
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