1. Sora CaJAGWR Seminar July 29, 2008 @Caltech Seiji Kawamura (National Astronomical Observatory of Japan)

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 moved above LISA band To be moved 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 Science by DECIGO 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. 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)

11. 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.

12. Roadmap 200708091011121314151617181920212223242526 Mission Objectives Test of key technologies Observation run of GW Detection 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) Pre-DECIGO DECIGO R&D Fabrication R&D Fabrication R&D Fabrication

13. DECIGO Pathfinder (DPF) Laser PD Floating Mirrors Drag-free S/C DECIGO DPF 20 cm 1,000 km Shrink the arm length from 1,000 km to 20 cm

14. Conceptual design and Technologies to demonstrate Thruster Local Sensor Floating mirror Stabilization system Laser Actuator Drag-free control system Laser source and stabilization system Control of Fabry-Perot interferometer Launch-lock system

15. Goal sensitivity of DPF

16. Expected sources

17. DPF S/C Size : 900mm cube Weight : 200kg SAP : 800W Battery: 50AH Downlink : 2Mpbs DR: 1GByte 3N Thrusters x 4 Stabilized Laser Interferometer Module Thruster Control Unit Solar Paddle Interfererometer Control Unit Housing Control Unit Mission Thrusters Central Processing Unit Bus Thrusters Satellite Bus (‘Standard bus’ system) DPF Payload Size : 900mm cube Weight : 100kg Power : 200W Data Rate: 600kbps Mission thruster x16 Power Supply SpW Comm.

18. DPF Mission Outline Orbit: Low-Earth (Altitude 500km), Sun-synchronous orbit (dusk-dawn) Launcher: Single launch by M-V follow-on (solid rocket booster under development) PBS (Post-Boost stage) for fine orbit insertion Launch: 2012 (target) Mission Lifetime: 1 year (nominal) 500km DPF Attitude Control: Gravity-gradient stab. Drag-free control with mission thrusters (Safe hold control by bus thrusters)

19. DPF Payload Fabry-Perot interferometer Finesse : 100 Length : 20cm Test mass : 1kg Signal extraction by PDH Laser source Nd:YAG laser (1064nm) Power : 25mW Freq. stab. by reference cavity Drag-free control Local sensor signal  Feedback to mission thrusters Weight : ~100 kg Size : ~90 cm cube Upper half of the satellite

20. JAXA ’ s Small satellite series Plan to launch 3 small satellites by the year 2015 using next-generation solid rocket booster Reduce time and cost by means of ‘Standard bus system’ Bus weight : ~ 200kg, Bus power : ~ 800W Downlink ~ 2Mbps, Data storage ~ 1GByte 3-axes attitude control SpaceWire-based data processing system 1 st mission (2011) : decided to be TOPS (Planetary science) 2 nd and 3 rd mission will be selected by 2009 March 15 Candidate missions (5 important candidates) DPF: GW observation DIOS: X-ray telescope for dark baryon investigation ERG: Plasma and particle detector for geo-space investigation Satellite for Magnet-plasma sail technology demonstration, … Image CG of TOPS (design has been changed now)

21. DPF Current status Laser frequency stabilization Mirror and its housing Micro thruster Drag-free control simulation Detailed design and noise investigation Required to submit Phase-A proposal R&D for core technologies DPF Launch: 2012 or 2013 as 2 nd or 3 rd standard small satellite of JAXA 2005 Jan. Submit a proposal of small GW detector mission 2006 Nov. Submit a proposal of GW-detector satellite as DECIGO pathfinder (DPF) 2007 Aug. Selected as a Pre-Phase-A mission R&D costs funded Brief History

22. Pre-DECIGO DECIGO Arm length100 km1000 km Mirror diameter30 cm1 m Laser wavelength 0.532  m Finesse3010 Laser power1 W10 W Mirror mass30 kg100 kg # of interferometers in each cluster 13 # of clusters14

23. Sensitivity of Pre-DECIGO S/N~14 for NS-NS@300Mpc, 10-20 events/year

24. 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 (Maryland), Sato (Hosei), Kanda (Osaka city), Takashima (ISAS), Ioka (Kyoto) Pre-DECIGO Sato (Hosei) 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 (Hosei) Laser Ueda (ILS) Musya (ILS) Drag free Moriwaki (Tokyo) Sakai (ISAS) Thruster Funaki (ISAS) Bus Takashima (ISAS) Data Kanda (Osaka city) Detector Numata (Maryland) Ando (Tokyo) Mission phase Design phase

25. DECIGO-WG Kazuhiro Agatsuma, Masaki Ando, Koh-suke Aoyanagi, Koji Arai, Akito Araya, Hideki Asada, Yoichi Aso, Takeshi Chiba, Toshikazu Ebisuzaki, Yumiko Ejiri, Motohiro Enoki, Yoshiharu Eriguchi, Masa- Katsu Fujimoto, Ryuichi Fujita, Mitsuhiro Fukushima, Ikkoh Funaki, 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, Kunihito Ioka, Koji Ishidoshiro, Hideki Ishihara, Takehiko Ishikawa, Hideharu Ishizaki, Hiroyuki Ito, Yousuke Itoh, Nobuyuki Kanda, Seiji Kawamura, Nobuki Kawashima, Fumiko Kawazoe, 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, Kouji Nakamura, Takashi Nakamura, Hiroyuki Nakano, Kenichi Nakao, Shinichi Nakasuka, Yoshinori Nakayama, Kazuhiro Nakazawa, Erina Nishida, Kazutaka Nishiyama, Atsushi Nishizawa, Yoshito Niwa, Kenji Numata, Masatake Ohashi, Naoko Ohishi, Masashi Ohkawa, Kouji Onozato, Kenichi Oohara, Norichika Sago, Motoyuki Saijo, Masaaki Sakagami, Shin-ichiro Sakai, Shihori Sakata, Misao Sasaki, Shuichi Sato, Takashi Sato, Naoki Seto, Masaru Shibata, Hisaaki Shinkai, Kentaro Somiya, Hajime Sotani, Naoshi Sugiyama, Yudai Suwa, Rieko Suzuki, Hideyuki Tagoshi, Fuminobu Takahashi, Kakeru Takahashi, Keitaro Takahashi, Ryutaro Takahashi, Ryuichi Takahashi, Tadayuki Takahashi, Hirotaka Takahashi, Takamori Akiteru, Tadashi Takano, Takeshi Takashima, Takahiro Tanaka, Keisuke Taniguchi, Atsushi Taruya, Hiroyuki Tashiro, Mitsuru Tokuda, Yasuo Torii, Morio Toyoshima, Kimio Tsubono, Shinji Tsujikawa, Yoshiki Tsunesada, Akitoshi Ueda, Ken-ichi Ueda, Masayoshi Utashima, Hiroshi Yamakawa, Kazuhiro Yamamoto, Toshitaka Yamazaki, Jun'ichi Yokoyama, Chul-Moon Yoo, Shijun Yoshida, Taizoh Yoshino

26. 1st International LISA-DECIGO Workshop Nov. 12-13, 2008 @ ISAS, Sagamihara, Japan Objectives: –Mutual understanding –Possible collaboration –Exposure of the missions to people in the neighboring fields Plenary talks: –Science of LISA & DECIGO, status of LPF & DPF 1 st circular w/ web page will be ready on Aug. 1

27. Summary DECIGO can detect GWs from the inflation as well as can bring us extremely interesting science. DPF has been selected as one of the 5 important mission candidates for small science satellite series; they plan to launch 3 missions in 5 years starting from 2011.

28. Let DPF fly!