An Antenna Pattern Correction Algorithm for Conical Scanning Spaceborne Radiometers: The CIMR Case

The rapid evolution of the effects observed in various areas of our planet related to climate change poses urgent questions about the knowledge of the state of the polar area and requires satellite acquisitions with fine spatial resolution and high accuracy to develop advanced products. The Copernicus Imaging Microwave Radiometer (CIMR) mission, based on a multifrequency microwave radiometer and designed to observe the ocean, sea ice, and Arctic environment, requires brightness temperature measurements with a total absolute uncertainty of 0.5 K and a spatial resolution of 5 km. This constraint demands very large reflectors with a gain value of tens of decibels. Mechanical constraints will be attained by using a mesh reflector, which guarantees the required resolution but with the drawback of a radiation pattern characterized by many grating lobes that contaminate the value of the brightness temperature associated with the boresight position. In this article, an antenna pattern correction (APC) is proposed to correct these effects. The algorithm takes advantage of an iterative formulation based on the Jacobi Method, providing a suitable correction that depends on the chosen spatial resolution. The APC algorithm was tested at both K- and Ka-bands with similar performance. Here, only the results from the latter are shown, as its antenna pattern is the most challenging among CIMR.

Automated summary

The rapid evolution of climate change effects requires satellite acquisitions with high accuracy and fine spatial resolution to assess the state of the polar area. The Copernicus Imaging Microwave Radiometer (CIMR) mission aims to observe the ocean, sea ice, and Arctic environment with specific requirements for brightness temperature measurements. A proposed antenna pattern correction (APC) algorithm corrects for the contamination of brightness temperature values caused by the use of mesh reflectors. The algorithm, based on the Jacobi Method, was tested at both K- and Ka-bands with similar performance.