Spatial Calibration and Imaging Performance Assessment of the Advanced Land Imager

n In 1998, the imaging properties of the Advanced Land Imager on the Earth Observing 1 (EO-1) satellite were calibrated at Lincoln Laboratory under simulated flight conditions. The spatial calibrations estimated the system transfer functions for the various spectral bands, and the line of sight of each detector, relative to a reference cube on the instrument. The Advanced Land Imager is a push-broom scanner. For each spectral band, a two-dimensional image is acquired one line at a time as the spacecraft moves over the scene. To reconstruct a normal image, we take into account the staggered placement of the detectors on the focal plane, the distortions in the optical system, and the speed and orientation of the spacecraft. Applying the line-of-sight calibration data, we have produced systemcorrected images from cues in the image data alone. We create browse images to show the entire scanned scene in any three of the available multispectral bands or in the panchromatic band. The panchromatic data have also been combined with the red, green, and blue multispectral data to produce natural-color images with ten-meter ground sampling distance. Following the launch of EO-1 in November 2000, the imaging performance was assessed from the on-orbit data. This was primarily done through analysis of images of bridges. In addition, the moon, stars, and planets were scanned. To reconstruct celestial images requires reference to the position and attitude data from the telemetry stream. The moon in particular provided valuable data to assess weak stray-light and ghost-image artifacts. In general, the images returned from orbit confirm the pre-launch calibrations, and fully satisfy the requirements developed for them at the start of the program.