Abstract
Abstract. INSAT-3D is an advanced meteorological satellite of ISRO which acquires imagery in optical and infra-red (IR) channels for study of weather dynamics in Indian sub-continent region. In this paper, methodology of radiometric quality evaluation for Level-1 products of Imager, one of the payloads onboard INSAT-3D, is described. Firstly, overall visual quality of scene in terms of dynamic range, edge sharpness or modulation transfer function (MTF), presence of striping and other image artefacts is computed. Uniform targets in Desert and Sea region are identified for which detailed radiometric performance evaluation for IR channels is carried out. Mean brightness temperature (BT) of targets is computed and validated with independently generated radiometric references. Further, diurnal/seasonal trends in target BT values and radiometric uncertainty or sensor noise are studied. Results of radiometric quality evaluation over duration of eight months (January to August 2014) and comparison of radiometric consistency pre/post yaw flip of satellite are presented. Radiometric Analysis indicates that INSAT-3D images have high contrast (MTF > 0.2) and low striping effects. A bias of <4K is observed in the brightness temperature values of TIR-1 channel measured during January–August 2014 indicating consistent radiometric calibration. Diurnal and seasonal analysis shows that Noise equivalent differential temperature (NEdT) for IR channels is consistent and well within specifications.
Highlights
INSAT-3D is an advanced geostationary meteorological satellite of ISRO launched on 26th July 2013
Navigation grids, ephemeris information, Radiometric look-up-tables (LUTs) for conversion of Count to Radiance or Count to Brightness temperature (BT) and other meta-information such as station ID, date and time of acquisition are available with product
RADIOMETRIC DATA QUALITY EVALUATION (RDQE) activities as described in Table-1 are carried out on products generated at MOSDAC facility and feedback on quality is provided to payload and data products teams
Summary
INSAT-3D is an advanced geostationary meteorological satellite of ISRO launched on 26th July 2013 It has two payloads namely six channel Imager and nineteen-channel Sounder. Radiometric quality evaluation carried out for Level-1 data products of Imager is described. Radiometric quality evaluation is carried out to study following aspects - a) Overall radiometric quality of scene in terms of dynamic range, feature sharpness, presence of striping due to detector nonuniformity and presence of image artefacts b) Radiometric performance in terms of mean brightness temperature (BT) of Land/Sea targets and validation with radiometric references c) Diurnal and Seasonal trends in BT values for identified targets and d) Sensor noise performance in terms of variation in Noise equivalent differential temperature (NEdT) for different IR channels. Scene Dynamic Range Edge Sharpness (MTF) Striping Noise Artefacts Mean Radiance/BT Signal-to-noise Ratio (SNR) Noise Equivalent Differential Temperature (NEdT)
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