Accession Number:

ADA180131

Title:

Prevention of Primary Mirror Contamination by Helium Purging.

Descriptive Note:

Technical rept.,

Corporate Author:

AEROSPACE CORP EL SEGUNDO CA CHEMISTRY AND PHYSICS LAB

Report Date:

1987-02-27

Pagination or Media Count:

115.0

Abstract:

Telescopes mounted on space platforms may be subject to performance degradation by the condensation of gaseous species on cryogenically cooled optical surfaces. Attenuations of the flux of impinging contaminants by a purging counterflow of helium He gas at the telescope entrance aperture have been calculated by a Monte Carlo procedure that follows individual trajectories selected at random. The calculations involve no significant approximations and should be quite accurate. In particular, multiple-collision trajectories are treated, employing the best available information on the atomic and molecular collision cross sections. Extensive calculations on protection of the Shuttle-mounted CIRRIS I and CIRRIS IA telescopes are presented which illustrate the extent of protection afforded. Keywords Cryogenic optics Helium purge Mirror contamination Molecular gas dynamics Monte Carlo calculation Spacecraft contamination.

Subject Categories:

  • Optical Detection and Detectors

Distribution Statement:

APPROVED FOR PUBLIC RELEASE