An inter-calibration method of infrared channels of FY-3C MERSI and VIRR using NPP/CrIS and Metop/IASI as the hyperspectral reference sensor is introduced. Based on FY-3C SNO collocated samples with CrIS and IASI, on early orbit, we analyze the calibration biases of infrared bands of MERSI and VIRR. The results show that the brightness temperatures (BT) from the MERSI observation and CrIS have a good consistency, and the BT biases present an approximately normal distribution and the mean BT bias is about -0.18K with standard deviation of 0.83K. When the scene BT is lower than 250 K, the result of MERSI is higher than that of CrIS, while the result of MERSI is lower at the more than 250K scene. The BT from VIRR shows significant systematic bias with respect to CrIS and the mean BT bias is about -0.65 K (channel 4) and -0.72 K (channel 5) at 250K scene with standard deviation of 0.15 K and 0.12 K, respectively. Long term monitoring analysis demonstrates the above biases are stable in the early 6 months. The inter-calibration results using different hyperspectral sensors IASI and CrIS indicate the MERSI/VIRR biases with respect to two reference sensors have a good consistency and this further verifies the reliability of the method. It provides significant information to further correct the calibration biases of MERSI and VIRR.
FY-3C/MERSI has some remarkable improvements compared to the previous MERSIs including better spectral response function (SRF) consistency of different detectors within one band, increasing the capability of lunar observation by space view (SV) and the improvement of radiometric response stability of solar bands. During the In-orbit verification (IOV) commissioning phase, early results that indicate the MERSI representative performance were derived, including the signal noise ratio (SNR), dynamic range, MTF, B2B registration, calibration bias and instrument stability. The SNRs at the solar bands (Bands 1–4 and 6-20) was largely beyond the specifications except for two NIR bands. The in-flight calibration and verification for these bands are also heavily relied on the vicarious techniques such as China radiometric calibration sites(CRCS), cross-calibration, lunar calibration, DCC calibration, stability monitoring using Pseudo Invariant Calibration Sites (PICS) and multi-site radiance simulation. This paper will give the results of the above several calibration methods and monitoring the instrument degradation in early on-orbit time.
Fengyun-3C (FY3C) launched on 23 Sep, 2013 and InfraRed Atmospheric Sounder (IRAS) start to
work on 30 Sep. Verification of instrument performance is an essential step before the L1 data
distributed operationally. Verification performance including: BlackBody temperature, channel noises,
radiance data assessment, Geo-location evaluation, instrument parameters trending, et al. Noise
Equivalent Differential Radiance (NEdN) of all IR channels meet specification and got improvement
on FY3B. IRAS L1 data are evaluated with Infrared Atmospheric Sounding Interferometer (IASI)
measurements onboard European MetOp-A satellite using cross comparison method, biases are within
1K for all IR channels except ch1 and ch9. Trends of instruments components temperature are also