On-orbit calibration of SeaWiFS.

Area of Science:

• Oceanography
• Remote Sensing
• Climate Science

Background:

• Ocean color climate data records (CDRs) demand high accuracy (5% absolute, 1% relative) for water-leaving radiances.
• Atmospheric correction amplifies sensor calibration errors, necessitating stringent radiometric stability for top-of-the-atmosphere (TOA) radiances (0.1%).

Purpose of the Study:

• To detail the calibration evolution and radiometric performance of the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) over its 13-year mission.
• To assess the uncertainties in calibrated TOA radiances and their impact on CDR generation.

Main Methods:

• Implemented a rigorous prelaunch and on-orbit calibration program for SeaWiFS.
• Utilized lunar, solar, and vicarious calibration techniques, refining methodologies over time.
• Quantified uncertainties in terms of accuracy (bias), precision (scatter), and stability (repeatability).

Main Results:

• Achieved long-term TOA radiance stability of 0.13% (lunar) and 0.30% (vicarious).
• Reported biases of 2%-3% (lunar) and 1%-2% (vicarious).
• Demonstrated precision levels of 0.10%-0.16% through various calibration methods.

Conclusions:

• The SeaWiFS instrument's exceptional radiometric stability over 13 years was critical for producing high-quality ocean color climate data records.
• The NASA Ocean Biology Processing Group's (OBPG) calibration program ensured the reliability and consistency of the data for climate studies.