An assessment of the on-orbit performance of the CALIPSO wide field camera

The Wide Field Camera (WFC) is one of three instruments in the CALIPSO science payload, with the other two being the Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP) and the Infrared Imaging Radiometer (IIR). The WFC is a narrow-band, push-broom imager that provides continuous high-spatial-resolution imagery during the daylight segments of the orbit over a swath centered on the CALIOP footprint. The instantaneous field of view of each WFC pixel is approximately 125 m × 125 m when projected on the Earth's surface from an orbit altitude of 705 km. The spectral band of the WFC, with a center wavelength of 645 nm and a FWHM bandwidth of 50 nm, is designed to match the Aqua MODIS instrument's channel 1. The primary WFC Level 1 products are radiance and reflectance registered to an Earth-based grid centered on the CALIOP ground track. "First light" WFC images were acquired on 18 May 2006 and routine data acquisition began in early June 2006. An initial science assessment of the WFC on-orbit performance was conducted based on analysis of the first twelve months of flight data. Comparisons of the WFC measurements with the well-calibrated Aqua MODIS channel 1 data were performed to evaluate the on-orbit radiometric performance of the WFC. Overall agreement is excellent, especially over bright deep convective clouds where the WFC measurements agree to within a few percent of MODIS. This paper provides a summary of our overall assessment of the on-orbit radiometric performance of the WFC.