REMOTESENS. ENVIRON.47:204-215 (1994) Comparative Analysis of Data Acquired by Three Narrow-Band Airborne Spectroradiometers over Subboreal Vegetation William T. Lawrence,* Darrel L. Williams,* K. Jon Ranson,* James R. Irons,* and Charles L. WalthaU* Calibrated radiance data were acquired with three airborne sensor systems on 8 September 1990 over a northern forest as part of the Forest Ecosystem Dynamics Multisensor Aircraft Campaign. The spectral data were acquired nearly simultaneously under extremely clear sky conditions with NASA's AVIRIS and ASAS imaging spectroradiometers, and an SE-590 spectroradiometer mounted on a NASA UH-1B helicopter. After atmospheric corrections were applied to these data, intercomparisons of nadir reflectance factor measurements from each of these sensors were made for four important vegetation communities including a bog and individual forest stands dominated by spruce (Picea sp.), eastern hemlock (Tsuga canadensis), and mixed northern hardwoods (dominated by Acer sp., Populus sp., and Betula sp.), respectively. The reflectance factor spectra from the different instru- ments were comparable for each of these cover types, suggesting the possible interchangeable use of the three datasets over comparable wavelength regions. These com- parisons also serve to graphically illustrate the impor- tance of applying atmospheric corrections to such data, even if acquired under extremely clear sky conditions. This remote sensing data set appears suitable for assessing the applicability of multistage, multisensor data in large- scale ecological research. * Department of Geography, University of Maryland, College Park *NASA/Goddard Space Flight Center, Biospheric Sciences Branch, Greenbelt Addresscorrespondence to WilliamT. Lawrence,Dept. of Geog- raphy, Univ.of Maryland, 1113LefrakHall, CollegePark, MD 20742. Received 15 October 1992; revised 10 July 1993. 204 INTRODUCTION The Forest Ecosystems Dynamics (FED) project (Smith et al., 1990; Levine et al., 1993) is fundamentally con- cerned with ecosystem pattern and process within northern forests across a hierarchy of both temporal and spatial scales. The underlying thesis of the FED project is that, through careful observation and model- ing, the interactions of the vegetation, soil, and energy components of the forest ecosystem can be understood. An important aspect of the FED project is the incorpora- tion of remote sensing data in the modeling effort in as many ways as possible, significantly reducing the requirements for field measurements and enhancing a synoptic, large-scale view of ecosystem function. The repetitive, multiscale, multispectral observation capabil- ities afforded by remote sensing platforms makes this type of data one of the premier tools for ecosystem modeling, environmental assessment, and the detection of global change. In this article, we compare atmospherically eor- reefed nadir reflectance factor spectra for four subboreal vegetation communities from observations made with three sensors flown as part of the FED Multisensor Aircraft Campaign (FED MAC) conducted 3-14 Sep- tember 1990. An initial analysis of calibrated radiance data from the three sensors showed the promise of interinstrument comparisons, even though there was a very strong impact of atmospheric path length on the at-sensor radiance (Fig. 1) (Lawrence et al., 1991). The instruments discussed in this article are: 1) the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) developed and managed by NASA's Jet Propul- sion Laboratory (JPL) (Green, 1990; Vane, 1987), and carried on-board a NASA ER-2 aircraft at an altitude of ca 20 km; 2) the Advanced Solid-State Array Spectrora- 0034-4257/94 / $7.00 ©Elset~erScienceInc., 1994 655 Avenueof the Americas,New York, NY 10010