Products and Data Analysis
CERES products include both solar-reflected and Earth-emitted radiation from the top of the atmosphere to the Earth's surface. The CERES instruments provide radiometric measurements of the Earth's atmosphere from three broadband channels. Cloud properties are determined using simultaneous measurements by other co-located imagers, such as the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Visible Infrared Imaging Radiometer Suite (VIIRS). Analyses of the CERES data lead to a better understanding of the role of clouds and the energy cycle in global climate change.
CERES Instruments and Satellites
There have been seven operational CERES instruments:
- The first CERES instrument, Proto-Flight Model (PFM) was launched on November 27, 1997 as part of the completed Tropical Rainfall Measuring Mission (TRMM).
- Two CERES instruments, Flight Models 1 and 2 (FM1 and FM2) were launched into polar orbit on board the EOS flagship Terra on December 18, 1999. FM2 ceased operations on January 10, 2025.
- Two additional CERES instruments, FM3 and FM4, were launched on board EOS Aqua on May 4, 2002.
- CERES instrument, FM5, was launched on board the Suomi National Polar-orbiting Partnership (S-NPP) satellite on October 28, 2011.
- The final CERES instrument, FM6, was launched on board the National Oceanic and Atmospheric Administration's (NOAA) Joint Polar Satellite System 1 (JPSS-1, now NOAA-20) satellite on November 18, 2017.
Technical Specifications and Operations
Instrument Detectors
The CERES instrument contains three detectors:
- One that measures the total returned energy (0.3 - 200 μm)
- Another that captures shortwave energy (0.3 – 5.0 μm)
- The last that measures infrared energy in the window channel (8 – 12 μm)
Note: The last CERES instrument, FM6 on NOAA-20, includes a longwave detector (5 - 35 μm) instead of the window channel.
Operational Modes and Advantages
Flying multiple satellites concurrently reduces the risk of a climate data record gap and provides adequate temporal sampling since clouds and radiative fluxes vary throughout the day. Having two instruments on one satellite allows operating one in cross-track mode for climate products and the other in a rotating azimuth plane to develop angular distribution models to adjust for anisotropy or allow validation with other instruments.
Performance and Calibration
The CERES instruments show significant improvements over the ERBE instruments, including lower noise, improved ties to ground calibration in absolute terms, and smaller fields of view. Calibration stability is typically better than 0.2% for all CERES instruments. Onboard calibration sources provide traceability to the prelaunch calibration of the CERES sensors tied to the International Temperature Scale of 1990.