한국광학회지 (Korean Journal of Optics and Photonics)

  • 제29권4호
  • /
  • Pages.166-172
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  • 2018
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  • 1225-6285(pISSN)
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  • 2287-321X(eISSN)
한국광학회 (Optical Society of Korea)
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우주환경에서 대형 반사경의 습기 방출에 의한 형상 변화 예측방법

Prediction Method for Moisture-release Surface Deformation of a Large Mirror in the Space Environment

  • 송인웅 (연세대학교 천문우주학과, 우주광학연구실) ;
  • 양호순 (한국표준과학연구원 첨단측정장비연구소 우주광학팀) ;
  • 김학용 (한국표준과학연구원 첨단측정장비연구소 우주광학팀) ;
  • 김성희 (한국항공우주연구원 위성연구본부) ;
  • 이회윤 (한국표준과학연구원 첨단측정장비연구소 우주광학팀) ;
  • 김석환 (연세대학교 천문우주학과, 우주광학연구실)
  • Song, In-Ung (Space Optics Laboratory (SOL), Department of Astronomy, Yonsei University) ;
  • Yang, Ho-Soon (Space Optics Team, Korea Research Institute of Standards and Science) ;
  • Khim, Hagyong (Space Optics Team, Korea Research Institute of Standards and Science) ;
  • Kim, Seong-Hui (Satellite Payload Development Division, Korea Aerospace Research Institute) ;
  • Lee, Hoi-Yoon (Space Optics Team, Korea Research Institute of Standards and Science) ;
  • Kim, Sug-Whan (Space Optics Laboratory (SOL), Department of Astronomy, Yonsei University)
  • 투고 : 2018.05.31
  • 심사 : 2018.07.09
  • 발행 : 2018.08.25
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⟨ 이전 논문 다음 논문 ⟩

초록

본 논문에서는 우주의 진공환경에서 반사경 코팅이 흡수한 습기를 방출하면서 나타나는 경면 형상의 변화를 예측하기 위한 새로운 방법론을 제안한다. 직경 50 mm, 두께 1.03 mm의 원형 시편과 간섭계를 통해 진공환경에서 나타나는 시편 형상 변화량을 측정하고 제르니케 프린지 다항식(Zernike fringe polynomial) 곡률항으로 나타내었다. 그 결과 습기 방출에 따른 코팅 스트레스는 152.7 Mpa로 계산되었다. 계산된 스트레스는 1.25 mm 두께 시편의 수치모사 모델에 적용하여 변화된 형상의 곡률항을 측정결과의 표준편차 이내($78.9{\pm}5.9nm$)로 예측할 수 있음을 검증하였다. 이 방법론을 2019년에 발사 예정인 차세대중형위성의 직경 600 mm 쌍곡면경에 적용, 습기 방출에 의한 경면 형상 변화를 계산하여 반사경의 초점거리가 약 $2.005{\mu}m$ 만큼 ?아짐을 예측하였다. 초점거리 변화는 광학 탑재체의 MTF를 한계공간주파수(Nyquist frequency)에서 2.3% 가량 낮추지만, 요구 사양을 만족하여 우주에서도 문제없이 운용 가능함을 확인하였다.

In this paper, we propose a new method to predict a mirror's surface deformation due to the stress of moisture release by a coating in the environment of outer space. We measured the surface deformation of circular samples 50 mm in diameter and 1.03 mm thick, using an interferometer. The results were analyzed using Zernike fringe polynomials. The coating stress caused by moisture release was calculated to be 152.7 MPa. This value was applied to an analytic model of a 1.25 mm thickness sample mirror, confirming that the change of surface deformation could be predicted within the standard deviation of the measurement result ($78.9{\pm}5.9nm$). Using this methodology, we predicted the surface deformation of 600 mm hyperbolic mirror for the Compact Advanced Satellite, which will be launched in 2019. The result is only $2.005{\mu}m$ of focal shift, leading to 2.3% degradation of modulation transfer function (MTF) at the Nyquist frequency, which satisfies the requirement.

키워드

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