The telescope to be onboard SPICA (Space Infrared Telescope for Cosmology and Astrophysics) has an aperture diameter of 2.5 m and its imaging performance is to be diffraction-limited at a wavelength of 20 μm at the operating temperature of <8 K. Because manufacturing precise autocollimating at mir- rors (ACFs) with sizes comparable to the SPICA telescope is not technically feasible, we plan to use sub-aperture stitching interferometry through ACFs for optical testing of the telescope. We have verified the applicability of the sub-aperture stitching technique to the SPICA telescope by performing stitching experiments in a vacuum at a room temperature, using the 800-mm telescope and a 300-mm ACF. We have also developed a new method to reduce uncertainties possibly caused by cryogenic and gravitational deformations of ACFs.

ABSTRACT
1. INTRODUCTION
2. MEASUREMENT
3. RESULTS
4. FUTURE PLAN
REFERENCES

• Asa Yamanaka(Graduate School of Science, Nagoya University)
• Hidehiro Kaneda(Graduate School of Science, Nagoya University)
• Mitsuyoshi Yamagishi(Graduate School of Science, Nagoya University)
• Toru Kondo(Graduate School of Science, Nagoya University)
• Takuma kokusho(Graduate School of Science, Nagoya University)
• Kotomi Tanaka(Graduate School of Science, Nagoya University)
• Misaki Hanaoka(Graduate School of Science, Nagoya University)
• Takao Nakagawa(Institute of Space and Astronautical Science)
• Mitsunobu Kawada(Institute of Space and Astronautical Science)
• Naoki Isobe(Institute of Space and Astronautical Science)
• Toshiaki Arai(Institute of Space and Astronautical Science)
• Takashi Onaka(Department of Physics, University of Tokyo)