Intersatellite Radiance Biases for the High-Resolution Infrared Radiation Sounders (HIRS) on board NOAA-15, -16, and -17 from Simultaneous Nadir Observations

Abstract

Intersatellite radiance comparisons for the 19 infrared channels of the High-Resolution Infrared Radiation Sounders (HIRS) on board NOAA-15, -16, and -17 are performed with simultaneous nadir observations at the orbital intersections of the satellites in the polar regions, where each pair of the HIRS views the same earth target within a few seconds. Analysis of such datasets from 2000 to 2003 reveals unambiguous intersatellite radiance differences as well as calibration anomalies. The results show that in general, the intersatellite relative biases are less than 0.5 K for most HIRS channels. The large biases in different channels differ in both magnitude and sign, and are likely to be caused by the differences and measurement uncertainties in the HIRS spectral response functions. The seasonal bias variation in the stratosphere channels is found to be highly correlated with the lapse rate factor approximated by the channel radiance differences. The method presented in this study works particularly well for channels sensing the stratosphere because of the relative spatial uniformity and stability of the stratosphere, for which the intercalibration accuracy and precision are mostly limited by the instrument noise. This method is simple and robust, and the results are highly repeatable and unambiguous. Intersatellite radiance calibration with this method is very useful for the on-orbit verification and monitoring of instrument performance, and is potentially useful for constructing long-term time series for climate studies.

Validation of the Calibration Coefficient of the GaoFen-1 PMS Sensor Using the Landsat 8 OLI

“…Table 5 shows the average relative differences (ARD) of the TOA radiance and TOA reflectance values for each band between GF-1/PMS and OLI images obtained over the Dunhuang and Golmud test sites. The definition of ARD is given in Equation (9).…”

Possible shift of spectral response function of the MODIS 6.8 μm water vapor channel causing a cold bias of 2–3 K

“…Considering that the IASI sensor is well calibrated to an uncertainty level below 0.2 K (Blumstein et al, 2007;Larar et al, 2010), one possible explanation of the discrepancy is that the MODIS WV channel may be biased cold. Such cold bias of Aqua/MODIS WV channel has been reported by Tobin et al (2006) In addition, Tobin et al (2006) noted that uncertainties of other MODIS infrared channels except temperature sounding channels range from near 0 K to 0.2 K. Although a direct comparison between IASI and MODIS is desirable, it may be available only over the polar regions, based on the socalled Simultaneous Nadir Overpasses (SNO) method (Cao et al, 2005). The equatorial crossing time of the IASI is 09:30 UTC, whereas it is 10:30 UTC for Terra/MODIS and 13:30 UTC for Aqua/MODIS.…”

10. The Calibration and Characterization of Earth Remote Sensing and Environmental Monitoring Instruments

“…Close, international-scale, collaborative efforts between a number of remote sensing institutions and agencies and national measurement institutes (NMIs) have produced many of these advances. For example, the Spectral Irradiance and Radiance Responsivity Calibrations with Uniform Sources (SlRCUS) facility at NIST [5 1, 80,271] and the National Laser Radiometry Facility (NLRF) at NPL are detectorbased facilities capable of accurately determining the subsystem or system level absolute spectral irradiance or radiance responsivity of remote sensing instruments. The facilities' tunable, laser-based light sources, with their high photon fluxes enabling higher signal-tonoise measurements, improve on previous monochromator-based and piece-part calculation approaches for the determination of remote sensing instrument responsivity.…”