NOTES: AIRS = Atmospheric Infrared Sounder; CAI = Cloud and Aerosol Imager; FTS = Fourier transform spectrometer; GOSAT = Greenhouse gases Observing Satellite; IASI = Infrared Atmospheric Sounding Interferometer; OCO = Orbiting Carbon Observatory; SCIAMACHY = Scanning Imaging Absorption Spectrometer for Atmospheric Chartography; SWIR = short-wavelength infrared; TIR = thermal infrared.

^aCrisp (2008); Crisp et al. (2008).

^bAkihiko Kuze, Japan Aerospace Exploration Agency, personal communication, 2009; Hamazaki et al. (2007); Shiomi et al. (2007).

^c<http://envisat.esa.int/instruments/sciamachy/>; Burrows et al. (1995); Noël et al. (1998); Buchwitz et al. (2005).

^dAumann et al. (2003); Chahine et al. (2008).

^ePhulpin et al. (2007); Crevoisier et al. (2009).

^fInstantaneous field-of-view/Swath.

^gThe uncertainty represents the estimate of random errors (e.g., the effects of detector noise) and additional systematic errors (e.g., bias caused by cloud and aerosol effects) unaccounted for or otherwise eliminated from the total error. Bias is reduced by successful validation efforts.

The GOSAT uncertainty is dominated by the precision (random errors). For OCO, Crisp et al. (2004) and Miller et al. (2007) discuss the observational system simulation experiments, including modeling of the OCO instrument performance characteristics, that led to an instrument design that would meet a measurement requirement of 1 part per million (ppm). The as-built OCO instrument performance was verified during prelaunch tests, which included direct solar observations. The analysis of the latter gave the best confirmation that the as-built instrument performance exceeded its design requirements.

The methods for bias reduction and validation are the same for GOSAT and OCO. Washenfelder et al. (2006) demonstrated the OCO validation concept and the essential role of ground-based measurements for meeting those objectives. Bösch et al. (2006) used these ground-based measurements to validate SCIAMACHY CO₂. The GOSAT team also plans to use the same validation sites and instruments. OCO planned to include and use Aeronet measurements. The OCO validation plan purposely located ground-based validation measurements at Atmospheric Radiation Measurement (ARM) Program sites to capitalize on the wealth of ancillary atmospheric and surface measurements.