Progress at ESA on high energy optics technologies

The Science Payload and Advance Concepts Office of the Science Directorate of the European Space Agency is responsible for developing and conducting a coherent and strategic technology program so as to ensure the feasibility of innovative advanced concepts for future science missions. These missions cover a wide range of disciplines ranging from astrophysics and fundamental physics to solar and planetary research, including exo-biology. The underpinning technology research and development is being conducted in collaboration with European industry and research institutes. The field of high energy photon optics for space applications has demonstrated substantial progress in the past decades, but continues, to face very interesting challenges for the future missions. Low specific mass (mass per effective collecting area) is the driving parameter for most future mission designs, both for space based astrophysics observatories and planetary missions. New technologies have to be explored for future applications, simultaneously achieving good angular resolution and low mass. The next generation of high energy astrophysics missions will require the development of much improved optical systems for the X-ray range, and the introduction of focussing imaging systems in the gamma-ray regime. While adequate detection systems are already available, or in the process of refinement and optimisation, the optical systems have posed the main hurdle in the design of new space missions. In this paper one potential alternative to the production of very lightweight X-ray optics, which is being investigated by ESA and its industrial partners, is discussed. First the applicability of the required optical design is addressed, followed by the currently ongoing work on the production facilities. Finally the impact of such optics on mission design is investigated based on the example of the X-ray Evolving Universe Spectroscopy mission XEUS. The cosmology mission XEUS [1-4] requires very large effective area, 30 m(2) at 1 keV, X-ray optics with high angular resolution of below 5" with a goal of 2". This implies a large aperture for a single telescope system, which will necessarily require assembly or deployment in space, and which will be formed by basic mirror modules known as petals. The petals must remain compatible with compact ground handling and production tools and will require minimum modifications to existing calibration facilities. Such optics are also envisaged for applications such as astrophysics observatories placed in very deep orbits or in the field of planetary remote sensing. In the latter application there are even stronger mass constraints although a more relaxed angular resolution requirement (e.g. arc minutes compared to arc seconds). Such optics systems have as a single common feature a dramatically reduced mirror thickness and therefore mass.