Thales Alenia Space has been involved in the design and the development of space observation instruments for over 40 years. This paper will explain why active optics is needed for next generation of instruments for Earth observation. We will also describe what kind of solution is preferred and why. We will give an overview of the development status on the associated technologies. Indeed, the future missions will have to deal with better performance, better optical quality while from manufacturing point of view, the total mass, the development schedule and the final cost have to be reduced. These constraints induce a new generation of solutions based on large entrance optics associated to high lightweight ratio which naturally provide solutions sensitive to gravity deformation. In these conditions, the enhancement of the final performance can only be guaranteed by using active optics in flight. A deformable mirror is therefore foreseen to be implemented in future large telescopes in order to correct manufacturing residues, ground/flight evolution including gravity. Moreover, low mass and low cost require more compact designs which entail solutions more sensitive to misalignment. An active positioning mechanism is then also needed in order to correct the telescope alignment during operation conditions. Thales Alenia Space has been selected by CNES to develop and qualify active optics building blocks and then to test and demonstrate the improvement that new active technologies can bring in a full size instrument representative of the next generation of observation instruments. An overview of the current development status and the achievable performances is given.

This study proposes a new way to manufacture large lightweight aspherics for space telescopes using Stress Mirror Polishing (SMP). This technique is well known to allow reaching high quality optical surfaces in a minimum time period, thanks to a spherical full-size polishing tool. To obtain the correct surface' aspheric shape, it is necessary to define precisely the thickness distribution of the mirror to be deformed, according to the manufacturing parameters. We first introduce active optics and Stress Mirror Polishing techniques, and then, we describe the process to obtain the appropriate thickness mirror distribution allowing to generate the required aspheric shape during polishing phase. Shape optimization procedure using PYTHON programing and NASTRAN optimization solver using Finite Element Model (FEM) is developed and discussed in order to assist this process. The main result of this paper is the ability of the shape optimization process to support SMP technique to generate a peculiar aspherical shape from a spherical optical surface thanks to a thickness distribution reshaping. This paper is primarily focused on a theoretical framework with numerical simulations as the first step before the manufacturing of a demonstrator. This "two-steps" approach was successfully used for previous projects.

The interferometer of the third generation meteorological satellite is composed by two corner cubes. The specifications, in terms of optical performances-wave front error (WFE)-and mechanical and thermal environments are very stringent compared to the actual knowledge. To answer to the mass, optical and mechanical specifications, a lightweighted hollow corner cube have been designed. An integration process based on enhanced molecular adhesion have been developed and tested in collaboration with CNES and LMA. This process required a fine polishing of the three mirrors of the corner cube before adhesion in order to obtain a very low flatness, roughness and angle precision. The mechanical resistance of the enhanced molecular adhesion process have been validated on three mockups submitted to shock and vibrations. The optical performances have been demonstrate on flight model corner cubes.

No abstract

No abstract