Helicopter MMR Reflectances During the Forest Ecosystem Dynamics - Multisensor Aircraft Campaign

Forest Ecosystem Dynamics Multisensor Airborne Campaign (FED MAC): Helicopter mounted Modular Multiband Radiometer Reflectance Measurements

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 to 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.

Surface directional radiances and reflectances were measured with a Modular Multiband Radiometer (MMR), in six of the spectral bands nominally corresponding to the Thematic Mapper bands, and the seventh band in the middle infrared region.

The Barnes Modular Multiband Radiometer (MMR) was designed to acquire multispectral radiance data over the visible, near infrared, middle infrared and thermal regions of the electromagnetic spectrum. It produces analog voltage responses to scene radiance in 8 spectral bands. Voltages from thermistors attached to
the instrument chopper and detectors are recorded to provide a means of compensating for thermal effects on sensor response and for calculation of target surface temperatures. The 8 bands are approximately 0.45 '-' 0.52,0.52 0.60, 0.63-0.69, 0.76-0.90, 1.15-1.30, 1.55-1.75, 2.08-2.35, 10.4-12.5 um. Bands 1-4 have silicon detectors and bands 5-7 have lead sulfide detectors. The MMR's dimensions are 26.4 cm by 20.5 cm by 22.2 cm and the device weighs 6.4 kg. The MMR is battery powered. Data logging was via a microprocessor-based Omnidata Polycorder where analog to digital conversions take place.

The NASA Bell UH-1B helicopter optical remote sensing system supported a data acquisition system consisting of a bore-sighted MMR; a color video camera; and two 35 mm flight research cameras loaded with color film (one with a 1 inch focal length and the other with a 6 inch focal length). Controller units for all the optical devices are rack-mounted inside the helicopter and are wired such that a single switch closure triggers all devices. The switch closure also activates an audible tone which is recorded on one of the two audio tracks of a Beta-format video recording system. The other audio track of the VCR was used to record cabin intercom conversations among the helicopter crew. If one desires to examine site conditions in greater detail, the higher resolution 35 mm still photography can be reviewed.