This dataset includes Level 1B (L1B) data products from the MODIS/ASTER Airborne Simulator (MASTER) instrument. The spectral data were collected during a single flight aboard a NASA WB-57 aircraft over California, Nevada, Oregon, and Washington, U.S., on 2003-08-27. This deployment was an instrument validation flight. Imagery was collected over the Cascade Mountains and Lake Tahoe. Data products include L1B georeferenced multispectral imagery of calibrated radiance in 50 bands covering wavelengths of 0.460 to 12.879 micrometers at approximately 25-meter spatial resolution. The L1B file format is HDF-4. In addition, the dataset includes flight path, spectral band information, instrument configuration, ancillary notes, and summary information for the flight, and browse images derived from each L1B data file.