Fig. 1. Rendering of the Nautilus fleet consisting of multiple unit telescope array during the space deployment phase.

Fig. 2. MODE lens consisting of two engineered optical surfaces, a multiple-order diffraction surface and a diffractive Fresnel surface balancing and compensating chromatic aberrations from refraction and diffraction.

Fig. 3. Nautilus unit telescope concept using 8.5 m MODE lens (on the right side) and 2.5 m MODE lens (on the left side). The 8.5 m MODE lens size is limited by the rocket fairing size. The optional 2.5 m aperture provides parallel imaging capabilities with a wide field of view, optimized for exoplanet transit search or surveys [1].

Fig. 4. (top) Schematic diamond turning process of the MODE lens’ diffractive Fresnel surface mold. (bottom) Diffractive Fresnel surface profile comparison between the design, the diamond turned mold, and the molded glass surface [4].

Fig. 5. Glass molded MODE lens ring segment using low transition temperature Ohara L-BSL7 glass.

Fig. 6. 3D model of KEYS with kinematic opto-mechanical design details and flexure model [6].

Fig. 7. (left) Fully assembled KEYS prototype and (right) SWLI results after fine alignment of the lens segments with the adjustment setscrews. After fine alignment, the height difference at the gap is within 20 μm (without relative tip/tilt between the two segments) [6].

Fig. 8. The real data from the deflectometry metrology system. (top) Live view from the deflectometry camera. (bottom-left) All eight segments are well-aligned against initial co-phasing status. The black line represents the actual size of the single segment. (bottom-right) Successfully detection of segment 3 being drifted from the reference position by tilting angle of 0.006°. (Note: X and Y axis units are in pixels.) [6].

Fig. 9. Closed-loop UV curing set-up with KEYS supporting the two MODE lens segment mockups. The deflectometry system provides the in-situ alignment feedback to control the KEYS [7].

Fig. 10. The acquired deflectometry pattern images. (left) The yellow boundary indicated the 3D printed mockups MODE segments. The attached slide glass provides a strong return signal representing the actual MODE lens surface case. The upper segment is mounted on a motorized KEYS support and the lower one is mounted on a manual adjustment support. (middle) The KEYS system was used to align the segments and saved the raw fringe image as a reference. (right) An intentional perturbation was applied to the upper segment and the misaligned was clearly detected by the shift of the pattern, which is processed by the deflectometry phase calculation [7].

Fig. 11. (left) The high optical throughput KEYS prototype, (middle) Newly updated flexure module with red arrows showing the degrees of adjustment per flexure module, (right) Two flexure modules on the prototype with adjusters installed [8].