The Japanese Space Gravitational Wave Antenna - DECIGO Amaldi7 @Sydney, Australia July 12, 2007 Seiji KAWAMURA, Masaki ANDO, Takashi NAKAMURA, Kimio TSUBONO, Takahiro TANAKA, Ikkoh FUNAKI, Naoki SETO, Kenji NUMATA, Shuichi SATO, Kunihito IOKA, Nobuyuki KANDA, Takeshi TAKASHIMA, Kazuhiro AGATSUMA, Tomomi AKUTSU, Tomotada AKUTSU, Koh-suke AOYANAGI, Koji ARAI, Yuta ARASE, Akito ARAYA, Hideki ASADA, Yoichi ASO, Takeshi CHIBA, Toshikazu EBISUZAKI, Motohiro ENOKI, Yoshiharu ERIGUCHI, Feng-Lei HONG, 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, Hideyuki HORISAWA, Mizuhiko HOSOKAWA, Kiyotomo ICHIKI, Takeshi IKEGAMI, Kaiki T. INOUE, Koji ISHIDOSHIRO, Takehiko ISHIKAWA, Hideharu ISHIZAKI, Hiroyuki ITO, Yousuke ITOH, Shogo KAMAGASAKO, Nobuki KAWASHIMA, Fumiko KAWAZOE, Hiroyuki KIRIHARA, Naoko KISHIMOTO, Kenta KIUCHI, Werner KLAUS, 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, Jun-ichi MIURA, 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, Tadayuki TAKAHASHI, Ryutaro TAKAHASHI, Ryuichi TAKAHASHI, Kakeru TAKAHASHI, Hirotaka TAKAHASHI, Akiteru TAKAMORI, 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

What is DECIGO? Terrestrial detectors (e.g. LCGT) LISA Strain [Hz-1/2] 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 moved above LISA band Terrestrial detectors (e.g. LCGT) LISA To be moved into TD band Strain [Hz-1/2] DECIGO Confusion Noise 10-4 10-2 100 102 104 Frequency [Hz]

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 Arm cavity Arm cavity Laser Mirror Photo- detector Drag-free S/C

Better best- sensitivity Why FP cavity? Implement FP cavity Shorten arm length Transponder type (e.g. LISA) Shot noise Shorten arm length Shot noise f1 Radiation pressure noise f-2 Implement FP cavity FP cavity type Better best- sensitivity Radiation pressure noise f-2 Shot noise f1 Strain Shot noise Transponder type (e.g. LISA) Frequency

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

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

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

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

Science by DECIGO 10-19 10-20 10-21 BH binary 10-22 10-23 10-24 10-25 10-26 (1000 M◎ z=1) BH binary Coalescence Formation of Super-massive BH Inflation 5 years NS binary (z=1) Coalescence 3 months Radiation pressure noise 1 unit Strain [Hz-1/2] Acceleration of Universe ⇓ Dark energy Shot noise Correlation (3 years) Verification of inflation 10-3 10-2 10-1 1 10 102 103 Frequency [Hz]

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.

Roadmap DICIGO Pathfinder (DPF) Pre-DECIGO DECIGO Mission 2007 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Mission Objectives Test of key technologies 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 R&D Fabrication R&D Fabrication R&D Fabrication DICIGO Pathfinder (DPF) Pre-DECIGO DECIGO

Pre-conceptual design and objectives of DPF Test of frequency stabilization system in space Test of drag-free system Test of locking system in space Rigid Cavity Floating mirror Test of laser in space Laser Thruster Actuator Local Sensor Observation of GW at 0.1 – 1 Hz

Deputy: Takashima (ISAS) 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) Detector Numata (Merryland) Ando (Tokyo) Science, Data Tanaka (Kyoto) Seto (NAOJ) Kanda (Osaka city) Satellite Funaki (ISAS) Design phase DECIGO pathfinder Leader: Ando (Tokyo) Deputy: Takashima (ISAS) Mission phase Detector Ando (Tokyo) Laser Ueda (ILS) Musya (ILS) Housing Sato (NAOJ) Drag free Moriwaki (Tokyo) Sakai (ISAS) Thruster Funaki (ISAS) Bus Takashima (ISAS) Data Kanda (Osaka city)

Current status There are now 140 members from 50 institutes in DECIGO working group Budget request (DECIGO R&D and fabrication of DPF, $20M) was rejected. We will submit budget request (R&D for DECIGO and DP, $10M) this year again. DPF working group was formally approved by JAXA/ISAS. We will submit budget request (R&D for DPF, $200K) to JAXA/ISAS.

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 been and will be working hard to obtain a budget to initiate R&D for DECIGO and DPF. We hope that we will obtain a budget for DECIGO R&D, and that DPF mission will be approved soon!

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