Helium purge flow prevention of atmospheric contamination of cryogenically cooled optics on orbiting infrared telescopes
Abstract
The ability of a He purge gas to protect the cryogenically cooled optics of orbiting infrared telescopes from the primary atmospheric contaminant, atomic oxygen, can be estimated by calculations simulating the HeO scattering events that would occur in the operating telescope. This paper reports results of accurate quantum mechanical calculations of the HeO differential cross sections sigma(theta, E) needed in such calculations. To facilitate the use of these cross sections, a simple separable function of E and theta is also given which provides an adequate representation of sigma(theta, E) for the entire range of relative collision energies studied, E = 0.021.66 eV.
 Publication:

International Journal of Engineering Science
 Pub Date:
 1983
 Bibcode:
 1983IJES...21..349H
 Keywords:

 Cryogenic Cooling;
 Helium;
 Infrared Telescopes;
 Oxygen Atoms;
 Purging;
 Scattering Cross Sections;
 Spaceborne Telescopes;
 Spacecraft Contamination;
 Atomic Collisions;
 Elastic Scattering;
 Gas Flow;
 Mathematical Models;
 Quantum Mechanics;
 Engineering (General)