The Climate Absolute Radiance and Refractivity Observatory (CLARREO) program objectives are recommended by the
NRC as a Tier-1 mission in its January 15, 2007 Earth Science Decadal Survey to be the key component of a future
decade-scale, global climate change observing system. The purpose of CLARREO is to make SI-traceable absolute
observations sensitive to the most critical, but least understood climate forcing phenomena, responses, and feedbacks.
NASA / LaRC is the mission lead as well as the Infrared (IR) instrument suite development lead. The Reflected Solar
(RS) instrument lead center has been assigned to GSFC where engineering risk reduction and science calibration
demonstration studies are being conducted on flight-like ETUs in anticipation of entry into Phase A.
The RS instrument suite (SOLARIS) is composed of multiple all-aluminum, slit-based, push-broom imaging spectroradiometers
of nearly identical construction. Each 'box' will be optimized to provide better than 8nm spectral resolution
(using multiple detector elements) over a specific spectral band covering the 320-2300nm total range with significant
overlaps to aid calibration. Optical design, fabrication, and alignment will provide for 500m nadir resolutions over a full
slit field of 100km from an approximately 600km polar orbit greater than 90% of the time. SNRs are likewise required to
exceed 33 for λ < 900nm and 25 for λ < 900nm. The maximum radiometric sensitivity to any naturally-occurring
polarized scene elements is expected to be between 0.5% - 0.75% for λ < 1000nm and λ <1000nm respectively. The RS
suite system will be capable of demonstrating a long-term, spectrally- & spatially-averaged, systematic radiometric error
of less than 0.3% (k=2).
Coupled with measurements from on-board GPS radio occultation receivers and inherent inter-calibration compatibility
with existing and future Earth science and operational missions, these measurements will provide a long-term
benchmarking data record for the detection, projection, and attribution of changes to our planet's climate system. The
CLARREO Project team successfully completed its Mission Concept Review (MCR) on November 17, 2010 at LaRC
with high marks and remains dedicated to the mission and its instruments. However, the launch readiness date (LRD) is
yet to be determined pending budget directive updates from the White House along with review of the IR and RS
calibration demonstration efforts (extended pre-Phase A).