FLIR at VLow

The following is the answer that Mr. Brooks A. Rowlett posted on the Admiralty Trilogy yahoo group in response to my question of whether there is any limitation to the effectiveness of sighting with FLIR when flying in the VLow altitude band.

On Mar 30, 2006, at 9:28 PM, Pete Maidhof wrote:

> I guess the idea came from limitations of AS radar vs VLow

> a/c to the effect of 10% of the max range.

The limitations on AS radar are from ground clutter reflecting radar

signals back into the radar set. This clutter acts as random energy

into the receiver and can be viewed as in effect increasing the noise

level of the radar, thus requiring a much stronger target signal to

distinguish from the noise.

Since the principle of operation is totally different, this is not an

effect on FLIR. Infrared light is still much shorter wavelength than

the radio waves of radar. This allows infrared receivers to have much

better resolution than radars, which ultimately allows you to funnel

the infrared signal into a signal processor of much greater capacity at

certain frequencies - a screen that displays an image for human eyes

feeding a human brain. The greater resolution of the output of the

signal and the magnificent pattern recognition ability of the human

allow much lower signal-to-noise ratio thresholds for discrimination of

targets from clutter (background).

There SHOULD perhaps be a WEATHER restriction on FLIR. It should have

a reduction at altitude over water when there is a lot of humidity

above the surface, or during fog. One of the myths in public

perception of IR sensors is that they see through clouds. In fact,

water vapor and water droplets are very powerful absorbers of IR

radiation. What IR excels at is seeing through dust and smoke -

battlefield haze. FLIR should also perhaps have a POSITIVE modifier at

VH altitudes due to how little water vapor is in the atmosphere at that

height.

- Brooks A. Rowlett

Thank you Brooks.