Visible/Infrared Intelligent Spectrometer Reflectances During the Forest Ecosystem Dynamics - Multisensor Aircraft Campaign

Forest Ecosystem Dynamics Multisensor Airborne Campaign (FED MAC): Visible/Infrared Intelligent Spectrometer (VIRIS) Reflectances

The Biospheric Sciences Branch (formerly Earth Resources Branch) within the Laboratory for Terrestrial Physics at NASA's Goddard Space Flight Center and associated University investigators are involved in a research program entitled Forest Ecosystem Dynamics (FED) which is fundamentally concerned with vegetation change of forest ecosystems at local to regional spatial scales (100 to 10,000 meters) and temporal
scales ranging from monthly to decadal periods (10 t 100 years). The nature and extent of the impacts of these changes, as well as the feedbacks to global climate, may be addressed through modeling the interactions of the vegetation, soil, and energy components of the boreal ecosystem.

The Visible/Infrared Intelligent Spectrometer (VIRIS), developed as the IRIS Mark IV by GER, Inc., and a portable illumination source (a spectralon coated hemisphere/baffle system employing 4, high-intensity, quartz line, 30 W bulbs) were used to characterize the reflectance of branch samples with needles attached (spruce and hemlock).

The VIRIS provides 2 nm spectral resolution from 0.4 - 1.1 um, and 4 nm spectral resolution from 1.1 - 2.5 um. The portable illumination source is placed at a standard distance (50 cm at an incidence angle of 35 degrees) from the branch samples. Single aged branch segments (1st-year and 2nd-year) were arranged in standard sample trays placed at a distance of 75 cm from the optical head of the VIRIS, yielding a field-of-view of 1.8 by 4.8 cm.

A total of three spectral scans were acquired and averaged to give a single VIRIS reflectance data set. Multiple data sets (i.e., each consisting of different branch segments) were acquired for each age class, using branch segments from the upper canopy of each tree. A software program known as the Integrated Data Management Module (IDMM) was developed at the University of New Hampshire and used for the analysis of VIRIS data. The program divides each spectral curve into a series of smaller, more workable spectral regions. From each spectral curve, 81 different reflectance, derivative and wavelength parameters were extracted (not all were included in this data set collection).