An L-band noise injection radiometer (NIR) has been designed and implemented by Helsinki University of Technology Laboratory of Space Technology for the SMOS (Soil Moisture and Ocean Salinity) mission of ESA [1]. The work is performed as a part of ESA's MIRAS Demonstrator Pilot Project-2 (MDPP-2) under a subcontract for EADS-CASA. Other partners in the MDPP-2 NIR project are Toikka Engineering Ltd. and Ylinen Electronics Ltd. NIR will work as a part of the MIRAS (Microwave Imaging Radiometer Using Aperture Synthesis) instrument. Its main purpose is (1) to provide precise measurement of the average brightness temperature scene for absolute calibration of the MIRAS unage map and (2) to measure the noise temperature level of the internal active calibration source for individual receiver calibration. The performance of NIR is a decisive factor of the MIRAS performance. The challenge in the implemented, so-called blind correlation, method is the fact that there is additional noise in the correlated signal due to using the noise injection method. The main objective of this paper is to demonstrate the feasibility of this technique.
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