Proceedings Article | 22 October 1999
Proc. SPIE. 3765, EUV, X-Ray, and Gamma-Ray Instrumentation for Astronomy X
KEYWORDS: Telescopes, Optical filters, Mirrors, Sensors, Satellites, Ultraviolet radiation, Inspection, Image sensors, Space telescopes, Extreme ultraviolet
The ALEXIS mission, serving as the first dedicated all-sky monitor in the extreme UV (EUV), has been collecting data since its launch in 1993. ALEXIS operates in a 70 degree inclination orbit at an altitude of 800 km. The ALEXIS science mission is to observe the cosmic UV background and to study variability of EUV sources. The ALEXIS experiment is composed of six telescopes. Although ALEXIS was designed for a one-year technology verification mission, the telescopes are still functioning with much the same effectiveness as at the beginning of the mission. The telescopes comprise: 1) layered synthetic microstructure (LSM) spherical mirrors, 2) thin foil filters, and 3) microchannel plate detectors, all enshrouded within the telescope body. The LSM mirrors select the bandpass for each telescope, while providing enhanced rejection of the HeII 304 angstrom geocoronal radiation. The filters, constructed either form aluminum/carbon or Lexxan/titanium/boron, serve to strongly erect the geocoronal radiation, as well as longer wavelength emission from bright O or B stars. Each telescope detector consists of two plates, the outermost of which is curved to accurately match the spherical focal surface of the mirror. By reviewing the ground and flight histories, this paper analyzes the flight performance of the filters, including the effects of long term exposure and the formation of pinholes.
