SIRTF's Delta II and gantry in visible and infrared light

This side-by-side comparison image shows SIRTF's Delta II rocket in the 
late afternoon before launch. On the left is a photograph in visible light, 
while on the right is a false color infrared image showing the launch 
vehicle in the way SIRTF would see it.

The coldest surfaces in the infrared image are blue/black while the hottest 
ones are yellow/white. The comparison between these two images reveals many 
interesting features of infrared light.

In many places the infrared image almost mimics a photographic negative, 
with light objects in the visible photograph looking dark in the infrared 
and vice versa. This is not a simple photographic effect, but a result of 
the fact that darker surfaces absorb sunlight more efficiently and become 
hotter than lighter surfaces. 

This thermal evidence of light absorption is very obvious on the Delta 
rocket, where the white surfaces are cooler than the darker ones. Upon 
close examination, this is even obvious on the lettering and designs on the 
various labels on the rocket and adjacent tower. In all of these places the 
heat patterns in the infrared image highlight the darker colors.

The infrared image also reveals a variety of features that can not be seen 
at all in the visible photograph. The rocket payload faring containing 
SIRTF is kept air conditioned, and several cool bands associated with this 
cooling can be seen on the upper white portion of the rocket. Also, the 
division between the lower empty fuel tanks and second stage rocket can be 
seen just below this as a cooler segment of the blue tube. 

The large gantry structure on the left shows a number of interesting 
thermal patterns. The hottest portion of the gantry is the area around the 
large white upper structure. Here the heat is being generated internally by 
the support and air conditioning equipment found in this structure, making 
it very hot even though it is painted white. The white panel on the upper 
right side of the gantry also shows some warm horizontal stripes. These 
trace the wamer metal beams on the inside of the panel that can't be seen 
in the photograph.