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J. Eur. Opt. Society-Rapid Publ. 22, 35( 2026)
Figure 3. Optical design and ray-tracing of the Kim TMS Type-I configuration for a 6.5-m diameter compact telescope( adapted from [ 17 ]). The co-location of the active M1 and the M3 enables a very short total length of the telescope along the optical axis.
FoV, which is crucial for precision observational analyses as well as for space adaptive optics utilizing natural guide stars.
Figure 2 compares ground-based Subaru Suprime-Cam( SC) and space-based JWST / NIRCam observations, highlighting differences between wide-field, seeing-limited imaging and diffraction-limited imaging with a smaller FoV. We also consider a“ denoised” diffraction-limited image reconstructed using an efficient-Transformer-based network [ 21 ]. We find that post-processing techniques such as deep-learning-based image restoration improve apparent image quality but do not mitigate the underlying spatial variations of the PSF in our data. These patterns limit PSF deconvolution accuracy, thereby impacting shape and photometry measurements and source deblending. As RWE increases, controlling PSF uniformity across the FoV becomes increasingly important at the optical design stage, with limitations that are difficult to fully address through post-processing alone.
3
Three mirror system categories based on tertiary mirror location diversity
Three-Mirror Anastigmat( TMA) optical systems and their variations— including those adopted for ground-based telescopes such as CMB-S4 [ 22, 23 ] and E-ELT and spacebased survey facilities such as Euclid and Roman— span a broad range of FoV and aperture sizes, associated with different observational science priorities. The image quality in such designs is governed by well-known optical scalings: geometrical aberrations generally increase with aperture diameter D, while the diffraction-limited angular resolution, often characterized by the Airy disk size, scales inversely with D. These competing fundamental relationships provide context for considering alternative telescope design architectures in the RWE framework.
Beyond their optical performance, the physical configuration, including the size and relative placement of mirrors, profoundly influences the overall telescope architecture and its concept of operations. The strategic location of the tertiary mirror( M3) can enable diverse telescope functionalities. The M3 location relative to the primary( M1) and secondary( M2) mirrors offers novel telescope form factors. These configurations are particularly well-suited for achieving large RWE, a crucial characteristic for space telescopes designed for the demands of the era of precision cosmology and astrophysics utilizing big data.
In the Kim TMS Type-I configuration, the 6.5-m M1 is near M3. This M1 – M3 grouping results in a highly compact optical design, with a total length along the optical axis of less than approximately 8 m, as illustrated in Figure 3 [ 17 ]. This design approach enables the packaging of a large-aperture telescope within a rocket’ s payload volume housed in its fairing. Furthermore, M1 is designed as an active deformable mirror, allowing real-time compensation of shape changes induced by gravitational and / or thermal deformations.
As another M3 location diversity option( Kim TMS Type-II), to facilitate an extremely large, deployable M1, such as an inflatable design, the remaining optical components( M2 and M3) are strategically positioned on the opposite side of the telescope from M1, as indicated by the dashed box in Figure 4 [ 19 ]. This configuration specifically incorporates a low-order deformable M3 grouped with M2. This M2 – M3 grouping allows independent assembly and testing of the downstream optical train, enabling integration with a large, deployable primary. A comparative summary of the specific telescope design parameters and optical performance for both Kim TMS Type-I / II configurations is presented in Table 1.
In addition to the traditional large étendue telescope design parameter space, large RWE space telescopes must consider their form factors to realize large aperture sizes during launch and / or deployment on orbit. The tertiary mirror location diversity becomes an important optical design category and optimization parameter.
4 Science opportunities enabled by large-RWE space telescopes
Large-RWE facilities maximize scientific return by combining survey depth with stable, high-resolution imaging. This architecture minimizes source confusion and enhances measurement fidelity, enabling the following key applications.