EO-1 Advanced Land Imager on-orbit radiometric calibration

The Advanced Land Imager (ALI) is the primary instrument on the first Earth Observing Mission (EO-1), under NASA´s New Millennium Program. On-orbit absolute radiometric calibration of this instrument relies primarily on solar calibration and involves pointing the ALI at the Sun with the aperture cover closed; deploying a Spectralon diffuser over the secondary mirror; and exercising a variable area subaperture located in the cover. The bimonthly solar calibration data is supplemented by daily internal reference lamp observations, monthly lunar observations, and periodic observations of ground truth targets. Each of the above techniques will be reviewed and the results compared to prelaunch calibration parameters. Additionally, the stability of the ALI during the course of its first year on orbit will be presented.