1. The Japanese Space Gravitational Wave Antenna - DECIGO Amaldi6 @Okinawa June 22, 2005 Seiji Kawamura, Takashi Nakamura, Masaki Ando, Kimio Tsubono, Naoki Seto, Shigeo Nagano, Takahiro Tanaka, Takehiko Ishikawa, Ken-ichi Ueda, Mitsuru Musha, Takashi Sato, Mizuhiko Hosokawa, Kenji Numata, Hisashi Hirabayashi, Tadashi Takano, Masa-Katsu Fujimoto, Atsushi Taruya, Yoshiaki Himemoto, Chul-Moon Yoo, Kenichi Nakao, Tomohiro Harada, Kunihito Ioka, Norichika Sago, Wataru Hikida, Shuichi Sato, Keiko Kokeyama, Mitsuhiro Fukushima, Hiroo Kunimori, Toshitaka Yamazaki, Masashi Ohkawa, Tatsuaki Hashimoto, Koh-suke Aoyanagi, Kazuhiro Agatsuma, Tomotada Akutsu, Hideki Asada, Yoichi Aso, Koji Arai, Akito Araya, Takeshi Ikegami, Koji Ishidoshiro, Kiyotomo Ichiki, Yousuke Itoh, Kaiki T. Inoue, Yoshiharu Eriguchi, Naoko Ohishi, Masatake Ohashi, Kenichi Oohara, Akira Okutomi, Shogo Kamagasako, Nobuki Kawashima, Mari Kawamura, Nobuyuki Kanda, Katsuhiko Ganzu, Kenta Kiuchi, Hideaki Kudoh, Kazuaki Kuroda, Kazunori Kohri, Yoshihide Kozai, Yasufumi Kojima, Shiho Kobayashi, Motoyuki Saijo, Masaaki Sakagami, Shihori Sakata, Misao Sasaki, Masaru Shibata, Hisaaki Shinkai, Naoshi Sugiyama, Hajime Sotani, Hirotaka Takahashi, Ryuichi Takahashi, Ryutaro Takahashi, Hideyuki Tagoshi, Hiroyuki Tashiro, Keisuke Taniguchi, Takeshi Chiba, Shinji Tsujikawa, Yoshiki Tsunesada, Masao Tokunari, Isao Naito, Hiroyuki Nakano, Kouji Nakamura, Atsushi Nishizawa, Yoshito Niwa, Choetsu Nozawa, Kazuhiro Hayama, Takashi Hiramatsu, Toshifumi Futamase, Kei- ichi Maeda, Hideo Matsuhara, Hiromi Mizusawa, Yasushi Mino, Osamu Miyakawa, Shinji Miyoki, Shinji Mukohyama, Toshiyuki Morisawa, Kazuhiro Yamamoto, Jun'ichi Yokoyama, Shijun Yoshida, and Taizoh Yoshino

2. Contents  What is DECIGO?  Current Status  Budget Situation  Preliminary Experiment  Summary

3. Gap between Terrestrial Detectors and LISA 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 Terrestrial Detectors (e.g. LCGT) Gap

4. DECIGO Bridges the Gap 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) The Japanese Space Gravitational Wave Antenna - DECIGO Deci-hertz Interferometer Gravitational Wave Observatory

5. Importance of Bridging the Gap New window brings new science! Observe inspiral sources that have moved above the LISA band Observe inspiral sources that have not yet moved into the ground-based detector band Especially inspiral of IMBH Completely new sources could be detected Completely new science could be obtained

6. Acceleration of Expansion of the Universe NS-NS (z ～ 1) GW DECIGO Output Expansion ＋ Acceleration? Time Strain Template (No Acceleration) Real Signal ? Phase Delay ～ 1sec (10 years) Seto, Kawamura, Nakamura, PRL 87, 221103 (2001)

7. DECIGO as a Future Gravitational Wave Detection Project in Japan TAM A Near Future NowPast DECIG O LCG T Far Future 1 st Priority

8. History of DECIGO 1999the LISA study group convened by Tsubono 2000Short-arm space antenna suggested by Kawamura 2001Space GW antenna WG convened as one of the possible future projects in NAOJ 2001Named as DECIGO in the PRL paper by Seto, Kawamura, Nakamura (DECIDE and GO) 20021 st DECIGO-WG meeting 20032 nd DECIGO-WG meeting (FP-type DECIGO suggested by Ando) 20053 rd DECIGO-WG meeting

9. Roadmap for DECIGO 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Design & Fabrication Observati on R& D Advanced R&D PF1 DECIGO Design & Fabrication Observatio n PF2

10. Pre-Conceptual Design for DECIGO LISA-type DECIGO - Shorter arm length Fabry-Perot-Cavity-type DECIGO - Even shorter arm length - Resonance of light in the cavity For both types - Better shot noise (higher power, shorter wavelength, larger mirror) - Better force noise (heavier mass)

11. Fabry-Perot Type DECIGO Drag- Free Satellite Around Lagrange Point Fabry- Perot cavity

12. Actuating Force in FP- DECIGO Anti-Drag + Anti-Gravity +Anti-GW Anti-Gravity +Anti-GW Proof Mass Outer Satellite The distance should be kept constant

13. Sensitivity of DECIGO Force noise= 1/100 of LISA’s

14. Preliminary Simulator for LISA-type DECIGO Built a preliminary simulator for DECIGO as a simulator for detecting the Earth’s gravity field around the Earth 地球 Distance: 50 km v MAX : 1 cm/s （ Doppler Shift: 20 kHz Satellite 2 Satellite 1

15. Schematic Diagram of the Preliminary Simulator Simulate Doppler shift by AOD Simulate distance by optical fiber Lock to mid- fringe by AOD Monitor FB to DDS Stabilized Frequency using 5 layer shielded cavity (like LISA)

16. Sensitivity of the Preliminary Simulator

17. Budget Situation for DECIGO and other GW Projects in Japan Budget request for “Frontier of All Wavelength Gravitational Wave Astronomy” to be submitted this fall - TAMA and CLIO - R&D for DECIGO - Pulsar Timing - Super-high frequency G.W. detection (Budget request for LCGT submitted this year from ICRR)

18. R&D for DECIGO Overall Tests Key Technologies Ground-based DECIGO Simulator (S. Kawamura, NAOJ) DECIGO-Pathfinder (M. Ando, Univ. of Tokyo) Measurement System (K. Tsubono, Univ. of Tokyo) Drag-free System (T. Ishikawa, JAXA-ISAS) Light Source (K. Ueda, ILS) Frequency Stabilization (T. Sato, Niigata Univ.) Evaluation of Light Source (M. Hosokawa, NICT) Satellite Technologies (?, JAXA- ISAS)

19. Objectives of the R&D R&D of subsystems Overall tests by ground-based simulator and DECIGO-Pathfinder1 R&D for optional technologies Defining the objectives and conceptual design of DECIGO-PF2 Establishing the conceptual design of DECIGO

20. Ground-Based Simulater Laser LF Pendulum Seismic Isolation System Test the system on earth as much as possible Investigate the system at low frequencies Observe GW at low frequencies LF Pendulum

21. Pathfinder Test the system which can be tested only in space (Drag-free system) Check if the measurement system works in space Observe GW at low frequencies This effort couples with the JAXA-ISAS’s new satellite plan Laser Drag Free System Measurement System One Small Satellite Resonated

22. Summary It is important to bridge the gap between terrestrial detectors and LISA. The Japanese space antenna DECIGO can bridge the gap. We have started serious investigation of DECIGO. We will submit a budget request for DECOGO R&D this fall. We hope that we will be able to start the R&D for DECIGO soon.