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Stray Light Analysis of a Compact Imaging Spectrometer for a Microsatellite STSAT-3

과학기술위성3호 부탑재체 소형영상분광기 미광 해석

  • Lee, Jin Ah (Department of Optical Engineering, Kongju National University) ;
  • Lee, Jun Ho (Department of Optical Engineering, Kongju National University)
  • Received : 2012.06.12
  • Accepted : 2012.07.25
  • Published : 2012.08.25

Abstract

과학기술위성3호 부탑재체인 COMIS(Compact Imaging Spectrometer)는 무게 4.25 kg의 소형영상분광기로써 지표면 및 대기과학을 연구할 목적으로 개발되었다. COMIS는 지표면, 대기, 수면으로부터 반사되는 태양 에너지를 고도 700 km에서 가시광 및 근적외선 영역(0.4 ~1.05 ${\mu}m$)에서 해상도 27 m, 관측폭 28 km, 파장 분해능 2 ~ 15 nm를 갖도록 결상 광학계와 분광 광학계로 구성된다. 먼저 지상 $27m{\times}28km$의 해당되는 지표면에서 반사된 빛은 COMIS의 결상 광학계에 의하여 상면에 위치한 $11.8{\mu}m{\times}12.1mm$의 선형 슬릿으로 맺히고, 이후 약 1.1배의 배율을 갖는 분광 광학계의 상면에 $1.4mm{\times}13.3mm$의 크기를 갖는 분광 스펙트럼 영상으로 나타난다. 이 때 부분 반사 및 산란 등에 의한 신호대잡음비(SNR, signal to noise ratio) 저하를 방지하기 위하여 렌즈 및 거울 면에 무반사 및 고반사 코팅이 적용되었고, 내부에는 미광 차단 구조물 등이 설치되었다. 미광 차단 설계의 적정성을 확인하기 위하여 미광 모델 수립과 상용 프로그램을 이용한 미광 해석을 수행하였다. 해석 결과 미광의 세기는 정상 결상 대비 무시할 정도의 값($10^{-5}$)으로 영상에는 실질적인 영향이 없음을 확인하였다.

This paper reports on the stray light analysis results of a compact imaging spectrometer (COMIS) for a microsatellite STSAT-3. COMIS images Earth's surface and atmosphere with ground sampling distances of 27 m at the 18~62 spectral bands (0.4 ~ 1.05 ${\mu}m$) for the nadir looking at an altitude of 700 km. COMIS has an imaging telescope and an imaging spectrometer box into which three electronics PCBs are embedded. The telescope images a $27m{\times}28km$ area of Earth surface onto a slit of dimensions $11.8{\mu}m{\times}12.1mm$. This corresponds to a ground sampling distance of 27 m and a swath width of 28 km for nadir looking posture at an altitude of 700 km. Then the optics relays and disperses the slit image onto the detector thereby producing a monochrome image of the entrance slit formed on each row of detector elements. The spectrum of each point in the row is imaged along a detector column. The optical mounts and housing structures are designed in order to prevent stray light from arriving onto the image and so deteriorating the signal to noise ratio (SNR). The stray light analysis, performed by a non-sequential ray tracing software (LightTools) with three dimensional housing and lens modeling, confirms that the ghost and stray light arriving at the detector plane has the relative intensity of ${\sim}10^{-5}$ and furthermore it locates outside the concerned image size i.e. the field of view of the optics.

Keywords

References

  1. J. H. Lee, T. S. Jang, H.-S. Yang, and S.-W. Rhee, "Optical design of a compact imaging spectrometer for STSAT3," J. Opt. Soc. Korea 12, 262-268 (2008). https://doi.org/10.3807/JOSK.2008.12.4.262
  2. J. H. Lee, C. W. Lee, Y. M. Kim, and J. W. Kim, "Optomechanical design of a compact imaging spectrometer for a microsatellite STSAT3," J. Opt. Soc. Korea 13, 193-200 (2009). https://doi.org/10.3807/JOSK.2009.13.2.193
  3. J. H. Lee, K. I. Kang, and J. H. Park, "A very compact imaging spectrometerfor the micro-satellite STSAT3," International Journal of Remote Sensing 32, 3935-3946 (2011). https://doi.org/10.1080/01431161003801328
  4. S.-J. Lee, J. Kim, J. H. Lee, C. W. Lee, K. I. Kang, and T. S. Jang, "Environmental test results of a flight model of a compact imaging spectrometer for a microsatellite STSAT-3," Korean J. Opt. Photon. 22, 1-6 (2011). https://doi.org/10.3807/KJOP.2011.22.4.184
  5. K.-W. Park and J.-U. Lee, "A study for stray light distribution of mobile phone camera consisting of two aspheric lenses," Korean J. Opt. Photon. 20, 6-15 (2009). https://doi.org/10.3807/HKH.2009.20.1.006
  6. J.-O. Park, W. K. Jang, S. Kim, H.-S. Jang, and S. Lee, "Starylight analysis of high resolution camera for a low-earth orbit satellite," J. Opt. Soc. Korea 15, 52-55 (2011). https://doi.org/10.3807/JOSK.2011.15.1.052
  7. H. S. Lee, S. W. Kim, T. Richards, I. Tosh, N. Morris, and M. Lockwood, "Stray-light analysis of Amon-Ra instrument," Proc. SPIE 5867, 46-57 (2005).
  8. M. J. Sholl, F. S. Grochocki, J. C. Fleming, R. W. Besuner, P. Jelinsky, and M. L. Lampton, "Stray light design and analysis of the SNAP telescope," Proc. SPIE 6675, 66750C (2007).
  9. G. L. Peterson, "Stray light calculation methods with optical ray trace software," Proc. SPIE 3780, 132-137 (1999).
  10. "LightToolsCore module user's guide," Optical Research Associates (2008).
  11. "$Zemax^{(R)}$ 12 optical design program user's manual," Radiant Zemax (2012).
  12. "CodeV reference manual," Optical Research Associates (2009).

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