抄録
An assessment of the influence due to footprint changes in microwave-radiation estimation taking Antenna Pattern Correction (APC) into account has been conducted. The APC is a powerful technique for obtaining precise data of microwave-radiation, though the pattern correction is much more sensitive to the footprint changes and additive noise. Therefore it is necessary to reduce the instability that is called 'ill-posed problem in inverse problem'. In this paper, we propose an iterative algorithm for APC based on Projection Onto Convex Sets (POCS) method and show its advantages by several numerical experiments based on the parametric data of the Advanced Microwave Scanning Radiometer (AMSR) of the Advanced Earth Observing Satellite-II (ADEOS-II) which is planned to be launched in 1998.
This algorithm uses a priori information to provide the convergence of the manifold including the solution iteratively. In this work, the changes in the foot-prints or the point-spread functions of AMSR along the orbit of the satellite (ADEOS-II) and the constraints in non-negative and smoothness conditions on brightness-temperature and introduced into the APC process as the a priori information.
From the results of numerical experiments, the following advantages can be obtained.
the ringing artefact along the temperature boundry can be reduced in comparison with those in the inversion by Fourier technique,
higher spatial resolution can be obtained without large scale matrix computation,
the levels of the spurious peaks in the proposed APC algorithm are reduced by 3 to 6 dB under the noisy environment in comparison with those in the direct inversion algorithm.
