1. The Japanese Space Gravitational Wave Antenna DECIGO TAUP2007 @Sendai, Japan Aug 11, 2007 Seiji Kawamura, Masaki Ando, Takashi Nakamura, Kimio Tsubono, Takahiro Tanaka, Ikkoh Funaki, Naoki Seto, Kenji Numata, Shuichi Sato, Nobuyuki Kanda, Takeshi Takashima, Kunihito Ioka, Kazuhiro Agatsuma, Tomotada Akutsu, Tomomi Akutsu, Koh-suke Aoyanagi, Koji Arai, Yuta Arase, Akito Araya, Hideki Asada, Yoichi Aso, Takeshi Chiba, Toshikazu Ebisuzaki, Motohiro Enoki, Yoshiharu Eriguchi, Masa-Katsu Fujimoto, Ryuichi Fujita, Mitsuhiro Fukushima, Toshifumi Futamase, Katsuhiko Ganzu, Tomohiro Harada, Tatsuaki Hashimoto, Kazuhiro Hayama, Wataru Hikida, Yoshiaki Himemoto, Hisashi Hirabayashi, Takashi Hiramatsu, Feng-Lei Hong, Hideyuki Horisawa, Mizuhiko Hosokawa, Kiyotomo Ichiki, Takeshi Ikegami, Kaiki T. Inoue, Koji Ishidoshiro, Hideki Ishihara, Takehiko Ishikawa, Hideharu Ishizaki, Hiroyuki Ito, Yousuke Itoh, Shogo Kamagasako, Nobuki Kawashima, Fumiko Kawazoe, Hiroyuki Kirihara, Naoko Kishimoto, Kenta Kiuchi, Shiho Kobayashi, Kazunori Kohri, Hiroyuki Koizumi, Yasufumi Kojima, Keiko Kokeyama, Wataru Kokuyama, Kei Kotake, Yoshihide Kozai, Hideaki Kudoh, Hiroo Kunimori, Hitoshi Kuninaka, Kazuaki Kuroda, Kei-ichi Maeda, Hideo Matsuhara, Yasushi Mino, Osamu Miyakawa, Shinji Miyoki, Mutsuko Y. Morimoto, Tomoko Morioka, Toshiyuki Morisawa, Shigenori Moriwaki, Shinji Mukohyama, Mitsuru Musha, Shigeo Nagano, Isao Naito, Noriyasu Nakagawa, Kouji Nakamura, Hiroyuki Nakano, Kenichi Nakao, Shinichi Nakasuka, Yoshinori Nakayama, Erina Nishida, Kazutaka Nishiyama, Atsushi Nishizawa, Yoshito Niwa, Masatake Ohashi, Naoko Ohishi, Masashi Ohkawa, Akira Okutomi, Kouji Onozato, Kenichi Oohara, Norichika Sago, Motoyuki Saijo, Masaaki Sakagami, Shin-ichiro Sakai, Shihori Sakata, Misao Sasaki, Takashi Sato, Masaru Shibata, Hisaaki Shinkai, Kentaro Somiya, Hajime Sotani, Naoshi Sugiyama, Yudai Suwa, Hideyuki Tagoshi, Kakeru Takahashi, Keitaro Takahashi, Tadayuki Takahashi, Hirotaka Takahashi, Ryuichi Takahashi, Ryutaro Takahashi, Takamori Akiteru, Tadashi Takano, Keisuke Taniguchi, Atsushi Taruya, Hiroyuki Tashiro, Mitsuru Tokuda, Masao Tokunari, Morio Toyoshima, Shinji Tsujikawa, Yoshiki Tsunesada, Ken-ichi Ueda, Masayoshi Utashima, Hiroshi Yamakawa, Kazuhiro Yamamoto, Toshitaka Yamazaki, Jun'ichi Yokoyama, Chul-Moon Yoo, Shijun Yoshida, Taizoh Yoshino

2. What is DECIGO? Deci-hertz Interferometer Gravitational Wave Observatory ( Kawamura, et al., CQG 23 (2006) S125-S131) Bridges the gap between LISA and terrestrial detectors Low confusion noise  Extremely high sensitivity 10 -18 10 -24 10 -22 10 -20 10 -4 10 4 10 2 10 0 10 -2 Frequency [Hz] Strain [Hz -1/2 ] LISA DECIGO Terrestrial detectors (e.g. LCGT) Confusion Noise have moved Above LISA band will move into TD band

3. Pre-conceptual design Differential FP interferometer Arm length: 1000 km Mirror diameter: 1 m Laser wavelength ： 0.532  m Finesse: 10 Laser power: 10 W Mirror mass: 100 kg S/C: drag free 3 interferometers Laser Photo- detector Arm cavity Drag-free S/C Arm cavity Mirror

4. Why FP cavity? Frequency Strain Radiation pressure noise f -2 Shot noise Shot noise f 1 Transponder type (e.g. LISA) Shot noise Shorten arm length Shot noise f 1 Radiation pressure noise f -2 Transponder type (e.g. LISA) Shorten arm length Implement FP cavity FP cavity type Better best- sensitivity

5. Drag free and FP cavity: compatible? Mirror S/C I S/C II

6. FP cavity and drag free : compatible? Local sensor Thruster Mirror Relative position between mirror and S/C S/C II S/C I

7. Drag free and FP cavity: compatible? Local sensor Thruster Mirror Relative position between mirror and S/C Actuator Interferometer output (GW signal) S/C II S/C I No signal mixture

8. Orbit and constellation (preliminary) Sun Earth Record disk Increase angular resolution Correlation for stochastic background

9. Inflation Formation of Super- massive BH Verification of inflation Goal Sensitivity and Science Frequency [Hz] Correlation (3 years) Strain [Hz -1/2 ] 10 -3 10 -2 10 -1 1 10 10 2 10 3 10 -19 10 -20 10 -21 10 -22 10 -23 10 -24 10 -25 10 -26 (1000 M ◎ z=1) BH binary Coalescence 5 years NS binary (z=1) Coalescence 3 months Acceleration of Universe ⇓ Dark energy Radiation pressure noise Shot noise 1 unit

10. Requirements Acceleration noise should be suppressed below radiation pressure noise –Force noise: DECIGO = LISA/50 (Acceleration noise in terms of h: 1, Distance: 1/5000, Mass: 100) –Fluctuation of magnetic field, electric field, gravitational field, temperature, pressure, etc. Sensor noise should be suppressed below shot noise. –Phase noise: DECIGO = LCGT×10 (Sensor noise in terms of h: 1, storage time: 10) –Frequency noise, intensity noise, beam jitter, etc. Thruster system should satisfy range, noise, bandwidth, and durability.

11. Roadmap 200708091011121314151617181920212223242526 Mission Objectives Test of key technologiesDetection of GW w/ minimum spec. Test FP cavity between S/C Full GW astronomy Scope 1 S/C 1 arm 3 S/C 1 interferometer 3 S/C, 3 interferometer 3 or 4 units DICIGO Pathfinder (DPF)  Ando’ s talk Pre-DECIGO DECIGO R&D Fabrication R&D Fabrication R&D Fabrication

12. Interim organization PI: Kawamura (NAOJ) Deputy: Ando (Tokyo ) Executive Committee Kawamura (NAOJ), Ando (Tokyo), Seto (NAOJ), Nakamura (Kyoto), Tsubono (Tokyo), Tanaka (Kyoto), Funaki (ISAS), Numata (Merryland), Sato (NAOJ), Kanda (Osaka city), Takashima (ISAS), Ioka (Kyoto) Pre-DECIGO Sato (NAOJ) Satellite Funaki (ISAS) Science, Data Tanaka (Kyoto) Seto (NAOJ) Kanda (Osaka city) DECIGO pathfinder Leader: Ando (Tokyo) Deputy: Takashima (ISAS ) Detector Ando (Tokyo) Housing Sato (NAOJ) Laser Ueda (ILS) Musya (ILS) Drag free Moriwaki (Tokyo) Sakai (ISAS) Thruster Funaki (ISAS) Bus Takashima (ISAS) Data Kanda (Osaka city) Detector Numata (Merryland) Ando (Tokyo) Mission phase Design phase

13. Current status There are now 140 members from 50 institutes in DECIGO working group Budget request (DECIGO R&D and fabrication of DPF, $20M, 6 years) was rejected. We will submit budget request (R&D for DECIGO and DP, $10M, 5-6 years) this year again. DPF working group was formally approved by JAXA/ISAS. Budget request (R&D for DPF, $65K, 1 year) to JAXA/ISAS was approved.

14. Summary DECIGO can not only bridge the gap between terrestrial detectors and LISA, but also open a very deep window at 0.1 – 10 Hz. DECIGO will use FP arm cavity to further improve the sensitivity. We have obtained some budget to initiate R&D for DPF. We hope that we will obtain a bigger budget for DECIGO R&D, and that DPF mission will be approved soon!