Molecular contamination testing with continuous-wave laser radiation at 1064 nm: de-risking activity for the LISA space mission

Abstract

This paper presents a set of developed tools and methods for the stray light analysis of the Compact Gas Imager, a new sensor concept to capture images of gases, featuring a peculiar optical concept. The disruptive optical concept requires an adaptation of existing tools and the development of new technics for accurate stray light analysis. The described approach consists in deriving the stray light requirements from the requirements for the gas concentration by use of theoretical models and a set of approximations. The coupling of analytical models implemented in MatLab with conventional FRED modeling allows the assessment of stray light performance, i.e. the estimate of the impact of ghost (parasite interferograms) and diffuse stray light on the Compact Gas Imager performance. The analysis of the simulation results highlights the design changes and countermeasures required to achieve the system performance objectives.The Compact Gas Imager concept associates interferometric and multispectral push broom imager technologies, thus the stray light methods and techniques discussed in the paper are suitable for a wide range of space applications.

Combined molecular and metallic particulate laser-induced contamination testing: de-risking activity for the LISA space mission

“…Considering this, LIC seems to be less of a concern for the LISA mission (1064nm, continuous-wave (cw), 150W/cm 2 ). Nonetheless, LIC did occur in the near-infrared (NIR) in multiple experimental studies [9,10,11] and the long mission duration, the financial and scientific significance of the mission, the lack of studies regarding the impact of potentially small deposits on the wavefront [12] and the estimation of the LISA working group that even a 2 nm deposit will start affecting the detection performance adversely (see Figure 1), lead to the conclusion that a comprehensive de-risking activity is crucial.…”

“…An initial series of parametric tests with varying contamination source temperature, test duration and fluence showed no indications for LIC deposit formation [12]. Thus, a 6-month long duration test was intended and a new sample holder was developed, which superposes 8 optics under test in order to improve the sensitivity for in-situ detection of thin deposits.…”