Infrared on the Pad

This side-by-side comparison image shows the Spitzer Space Telescope'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 the telescope 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
the Spitzer Space Telescope 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.

Image Credit: NASA/JPL-Caltech/R.Hurt

Credit: JPL