Space Shuttle Erratum: Passive vs. Active IR

A recent link to an article at STR concerning a possible military angle to the Columbia Space Shuttle mission caused me to raise an eyebrow after only the very first sentence; "Night vision actively makes visible things hidden in darkness." The article continues in the assertion that night vision technology, as well as a possible imaging system on Columbia , is 'active,' in that it projects energy in order to 'see in the dark.' Night vision technology is, in fact, 'passive,' in that it uses detectors sensitive to the infrared energy given off by objects in order to 'see in the dark' and does not require an external source of infrared energy to illuminate objects.

Infrared energy is a form of light below the perceptible limit of human vision, and just as the human eye is able to detect incident energy in the visible spectrum, so too can infrared sensors detect energy in the infrared energy band. An 'active' night vision technology, one that projects an infrared beam, would be easily detected by another passive detector. This, obviously, is the inherent weakness in active technology, whether it be a visible photoflash or an 'invisible' infrared beam. Just consider what happens every time an Iraqi radar site 'paints' a jet fighter with a radar beam; the energy is detected and used to guide a missile back to the source of energy. Much to be said for 'see and not be seen,' obviously.

The difference between 'active' and 'passive' is central to understanding the fundamental shortcoming of this article; infrared imaging/night vision does not require an energy beam to create images. A quick Google search will yield many links to other multispectral imager missions , and Yoichi Shimatsu's allusion to 'ghostly apparitions' (spectres) is, well, silly. The imager simply viewed the environment in the visible, ultraviolet, and infrared areas of the electromagnetic spectrum. Likewise, the references to 'sprites' was equally ridiculous. Mankind is still discovering the wonders of the natural world, and scientists are sometimes given to providing fanciful names for natural phenomena.

The references to nuclear energy are certainly alarming, but misleading. It's probably not very widely known that most household smoke detectors contain Americium 241, and while they are certainly not completely harmless, they probably aren't very likely to cause ghostly sprites to zap your home. I would imagine an enourmous space shuttle hurtling through the atmosphere and scrubbing off electrons wildly due to friction might pose a greater source of spritely attraction than simply flicking the 'on' switch to a camera.

I can't really fault Rob for passing on the link to this article since the service provided by Strike The Root is one of providing daily links to articles of interest; it's not possible for one person to screen every interesting article on the 'net, and the reader is the ultimate arbiter of the trustworthiness of the information. Hopefully Root Strikers will perform after-the-fact verification or critique of contributions. Were this merely something hanging around Grabbe's website, I wouldn't have written, but seeing it linked to by STR, as well as by, I was compelled to try to set the record straight in this regard. I don't regard Grabbe's website as credible, and in the aftermath of this piece by Shimatsu, I wonder how many others will come to the same conclusion.

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