Integrated ray tracing simulation of annual variation of spectral bio-signatures from cloud free 3D optical earth model

Dongok Ryu, Sug Whan Kim, Dae Wook Kim, Jae Min Lee, Hanshin Lee, Won Hyun Park, Sehyun Seong, Sun Jeong Ham

Research output: Chapter in Book/Report/Conference proceedingConference contribution

8 Scopus citations


Understanding the Earth spectral bio-signatures provides an important reference datum for accurate de-convolution of collapsed spectral signals from potential earth-like planets of other star systems. This study presents a new ray tracing computation method including an improved 3D optical earth model constructed with the coastal line and vegetation distribution data from the Global Ecological Zone (GEZ) map. Using non-Lambertian bidirectional scattering distribution function (BSDF) models, the input earth surface model is characterized with three different scattering properties and their annual variations depending on monthly changes in vegetation distribution, sea ice coverage and illumination angle. The input atmosphere model consists of one layer with Rayleigh scattering model from the sea level to 100 km in altitude and its radiative transfer characteristics is computed for four seasons using the SMART codes. The ocean scattering model is a combination of sun-glint scattering and Lambertian scattering models. The land surface scattering is defined with the semi empirical parametric kernel method used for MODIS and POLDER missions. These three component models were integrated into the final Earth model that was then incorporated into the in-house built integrated ray tracing (IRT) model capable of computing both spectral imaging and radiative transfer performance of a hypothetical space instrument as it observes the Earth from its designated orbit. The IRT model simulation inputs include variation in earth orientation, illuminated phases, and seasonal sea ice and vegetation distribution. The trial simulation runs result in the annual variations in phase dependent disk averaged spectra (DAS) and its associated bio-signatures such as NDVI. The full computational details are presented together with the resulting annual variation in DAS and its associated bio-signatures.

Original languageEnglish (US)
Title of host publicationInstruments, Methods, and Missions for Astrobiology XIII
StatePublished - 2010
EventInstruments, Methods, and Missions for Astrobiology XIII - San Diego, CA, United States
Duration: Aug 3 2010Aug 5 2010

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


ConferenceInstruments, Methods, and Missions for Astrobiology XIII
Country/TerritoryUnited States
CitySan Diego, CA


  • Astrobiology
  • Disk Averaged Spectrum(Spectra)
  • Earth Observing Simulation
  • Extra-solar Planet
  • Full 3D Earth Model
  • Integrated Ray Tracing
  • Spectral Bio-signature of the Earth
  • Terrestrial Planet Finding

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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