High image quality and complex, refractive optical systems, as those used in remote sensing applications, are, in general, very difficult to be manufactured with the required performance. This can be charged to the high sensitivity of such systems to the fabrication tolerances, mainly concerning the relative alignment of the optical components with respect to each other. When the system does not achieve the expected quality, the puzzle is to identify where the problems lies. This is even worsened when the number of optical elements becomes high. Due to these facts, some misalignment characterization and estimation techniques based on Bayesian estimators and wavefront measurements have been proposed in the literature. This paper is the result of a deep study and investigation of these techniques, with emphasis on an application to an intentionally simple system for the sake of illustration that highlights conceptual issues that could be extended to more realistic, complex optical systems. With this purpose, the sensitivity of the wavefront Zernike coefficients to the misalignment parameters, its use in a parameter estimator design that includes nonlinear terms, the study of the system observability, and a statistical analysis of the estimator performance considering the observation noise are addressed in details. Numerical simulation results for the simple system are shown. We also present insights on how to apply the technique to the alignment of a 11-lens optical system used in the Brazilian remote sensing camera MUX, that will fly on-board the upcoming Sino-Brazilian satellites CBERS 3&4.

This paper aims to present the optical system of the Multispectral Camera MUX that is part of the payload for the CBERS 3 & 4 satellite (China Brazil Earth Resources Satellite). The CBERS program was created by Brazil and China for the development of Earth remote sensing satellites. The MUX camera is being developed by the Brazilian company OPTO ELETRÔNICA S.A. and consists of a multispectral camera with four spectral bands covering the wavelength range from blue to near infrared (from 450nm to 890nm) with a ground resolution of 20m and a ground swath width of 120 km. Besides MUX camera (optical system, signal processing electronics and mechanical frame), this company is also developing the Ground Support Equipment -GSE of this camera and is responsible for structural and environmental tests. At the moment, the project is in the Qualification Model (QM). During this phase of the development, the camera shall be submitted to several tests, including environmental, optical and structural tests with the objective of qualify the project and start the flight models manufacturing.

The purpose of this paper is to present the optical system developed for the Wide Field imaging Camera -WFI that will be integrated to the CBERS 3 and 4 satellites (China Brazil Earth resources Satellite). This camera will be used for remote sensing of the Earth and it is aimed to work at an altitude of 778 km. The optical system is designed for four spectral bands covering the range of wavelengths from blue to near infrared and its field of view is ±28.63º, which covers 866 km, with a ground resolution of 64 m at nadir. WFI has been developed through a consortium formed by Opto Electrônica S. A. and Equatorial Sistemas. In particular, we will present the optical analysis based on the Modulation Transfer Function (MTF) obtained during the Engineering Model phase (EM) and the optical tests performed to evaluate the requirements. Measurements of the optical system MTF have been performed using an interferometer at the wavelength of 632.8nm and global MTF tests (including the CCD and signal processing electronic) have been performed by using a collimator with a slit target. The obtained results showed that the performance of the optical system meets the requirements of project.

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The AWFI camera (Advanced Wide Field Imaging Camera) is part of the payload for the AMAZONIA 1 satellite. This camera and its GSE -Ground Support Equipments, are under development by the Brazilian company Opto Eletrônica S.A. AWFI camera will be used for remote sensing of the Earth and will image a ground swath of 754 km, with a ground resolution of 40m at nadir, in four spectral bands that cover the range of wavelength from 450nm to 890nm. This camera is composed of the optoelectronic block and the signal processing electronics. The opto-electronic block is composed of three identical optical channels and a mechanical frame. This work aims at presenting the optical system developed for the optical channel of this camera and its theoretical performance.