Trade-offs for very large space telescope mirrors

Some of the key questions in science, such as star formation, the search for Earth like exoplanets, can only be answered by telescopes, with primary mirrors with diameters larger than 8 meters – such as the recently launched James Webb telescope.

Future large space telescopes need new technologies to meet their high performance requirements at an affordable cost.

TDE and Airbus, France, recently completed an activity to study two different telescope concepts – one with a 4m primary mirror, and another with a 50 square meter area (approximately double the size of Webb).

The concept instruments were bound by several constraints. The boundary set for achievable apertures was the new Ariane 6 launcher capability. While the scientific requirements were bound by the performance gap in the UV-Visible wavelength domain, which allowed the activity to focus on technologies consistent with room temperature type operating conditions (similar to Hubble). This avoided the additional cryogenic complexity required for IR and Far-IR missions.

The activity identified several enabling key technologies and defined a roadmap for their development. Among these technologies are large monolithic mirror polishing techniques, active optics, deployable space structures, low-cost, lightweight optics, and wave front sensing and control methods. 

The results showed that both telescopes, the 4m monolithic and 16m deployable concepts, are feasible and can be realised in Europe within a 10 to 15 year timeframe based on available and anticipated technologies, manufacturing and test facilities.

T716-403MM closed in 2021.