Measurements
The Multi-angle Imaging SpectroRadiometer (MISR) aboard the EOS-Terra satellite makes global, near-simultaneous, multi-spectral, and multi-angle radiometric measurements of the Earth since 2000. MISR has nine separate cameras providing viewing zenith angles relative to the surface reference ellipsoid of 0°, 26.1°, 45.6°, 60.0°, and 70.5°, with one camera (designated AN) pointing toward nadir, one bank of four cameras (designated AF, BF, CF, and DF in order of increasing off-nadir angle) pointing forward in the along-track orbital direction, and one bank of four cameras (designated AA, BA, CA and DA) pointing in the backward direction. It takes approximately 7 minutes to view a given scene from all nine cameras. Each camera has four narrow spectral bands centered at 446, 558, 672, and 866 nm.
MISR has a 14-bit radiometric resolution and does not saturate over bright surfaces such as snow and thick clouds. MISR also has high radiometric stability with an absolute calibration uncertainty of better than 4%. Since launch, MISR has kept the radiometric drift to nearly undetectable levels and angle-to-angle image co-registration to sub-pixel accuracies.
Local Observation Time and Length of Data Record
10:30 AM; 2001-2017 provided to GEWEX; 2000-present available through the Langley DAAC
Spatial Resolution
1.1 km (cloud detection and CZ retrieval), 17.6 km (CA retrieval)
Cloud Detection
multi-spectral (VIS/NIR) and multi-angle; combination of static and dynamic thresholds
Retrieval Methodology
CA stratified by altitude in 500 m bins is calculated by combining three separate MISR cloud masks that are optimized for the underlying surfaces, namely ice-free ocean, snow-free land, and snow and ice covered surfaces. CZ is retrieved using stereo photogrammetric techniques. CZ is also corrected for cloud-motion effects caused by winds, which are derived using a triplet set of MISR cameras. MISR cloud height retrievals do not rely on the validity of atmospheric temperature profiles or radiometric calibration. The joint distributions of CA and CZ are summarized in the MISR Cloud Fraction By Altitude product, which has been degraded to the GEWEX altitude classification of Low, Middle, and High.
Ancillary Input
Snow/Ice mask
Surface Elevation
References
Di Girolamo, L., A. Menzies, G. Zhao, K. Mueller, C. Moroney, and D.J. Diner, 2010: MISR Level 3 Cloud Fraction by Altitude Theoretical Basis, JPL D-62358, Jet Propulsion Laboratory, Pasadena, CA, 24 pp.
Data Distribution
Di Girolamo, L., A. Menzies, G. Zhao, K. Mueller, C. Moroney, and D.J. Diner, 2010: MISR Level 3 Cloud Fraction by Altitude Theoretical Basis, JPL D-62358, Jet Propulsion Laboratory, Pasadena, CA, 24 pp.