Timeseries of noise characteristics and instrument error correlations for the High Resolution Infrared Radiation Sounder on the NOAA-15 satellite

The High Resolution Infrared Radiation Sounder (HIRS) is a 20-channel infrared sounding radiometer which has flown on 16 polar orbiting meteorological satellites between 1978 and the present day. As part of the FIDelity and Uncertainty in Climate data records from Earth Observation (FIDUCEO) project to bring together the sciences of metrology and earth observation, we have undertaken a detailed analysis of all major sources of uncertainty in HIRS measurements. The figure, which accompanies an upcoming paper by Holl, Mittaz, and Merchant, illustrates one year of noise and error characteristics on HIRS channel 1 (14.95 µm) on the National Oceanic and Atmospheric Administration (NOAA)-15 satellite. The top panel shows all individual counts for the calibration views observing deep space. The middle panel shows the Allan Deviation for each pair of space views; this is a robust characterisation of instrument noise. The bottom panel shows the Pearson correlation between the errors (as measured by anomalies within a set of calibration measurements) for the space counts between channel 1 and channels 2–7. The figure illustrates there is a significant and temporally varying error covariance for the space views. The upcoming paper explores this in much more detail.