P063 ASTROD AND I Progress Report

ASTROD and ASTROD I: Progress Report: 

ASTROD and ASTROD I: Progress Report Sun Inner Orbit Earth Orbit Outer Orbit Launch Position . Earth (800 days after launch) L1 point Laser Ranging S/C 2 S/C 1 100 fW ASTROD I Orbit: 2 encounters with Venus to swing the spacecraft to the other side of the Sun to conduct Shapiro time delay measurement and to measure Venus multiple moments. An orbit design for a 2012 launch is as follows: ASTROD The objectives of the ASTROD (Astrodynamical Space Test of Relativity using Optical Devices) mission are threefold --- to discover and explore fundamental physical laws governing matter, space and time via testing relativistic gravity with 3-5 orders of magnitude improvement, to improve measurement of the solar-system parameters and to detect and observe gravitational waves from massive black holes and galactic binary stars in the frequency range 50 μHz to 5 mHz. A desirable implementation is to have two spacecraft in separate solar orbit carrying a payload of a proof mass, two telescopes, two 1-2 W lasers, a clock and a drag-free system, together with a similar L1/L2 spacecraft. The 3 spacecraft range coherently with each other using lasers. ASTROD I with one spacecraft ranging optically with ground stations is a first step for a full ASTROD (Astrodynamical Space Test of Relativity using Optical Devices) mission. The goals are testing relativity with gamma measured to 10-7, measuring solar-system parameters more precisely and improving the present-day sensitivity for gravitational wave detection using Doppler tracking by radio waves. The spacecraft is to be launched into an inner solar orbit with initial period about 290 days to encounter Venus twice to receive gravity-assistance for achieving shorter period (165 days or less) for a sooner measurement of Shapiro time delay.  In this paper, we report on the progress since AMALDI5 for ASTROD and ASTROD I. Orbit motion of the 3 spacecraft of ASTROD around the Sun gives different modulation for a gravitational-wave signal and a solar g-mode signal. Reachable low-frequency-end sensitivity is discussed. For ASTROD I, we present the orbit design and orbit simulation, preliminary accelerometer development result, one-way transmit-receive-timing instrumental development, and ground laser station development. We discuss the atmosphere transmission noise., In Poster # 6timing noise, spacecraft environmental noise, test-mass sensor back-action, and test mass-spacecraft control-loop noise and stiffness. Low-frequency noise in acceleration are emphasized. Their effects on position are discussed. For weaklight phase-locking, please see poster #62. The gravitational-wave sensitivity curve of ASTROD and the strength of various sources. The sensitivity is for 1 yr observation with S/N=5. A simulation of the accuracy for determining the relativistic parameters β and γ, and the solar quadrupole parameter J2 gives 10-7, 10-7 and 10-8 for their uncertainty Δβ and Δγ, and ΔJ2. In this simulation, we assume a 10 ps timing accuracy and 10-13 ms-2Hz-1/2 inertial sensor/accelerometer noise. 10 ps timing is already achieved in satellite laser ranging. The accelerometer requirement as compared with LISA is shown in Poster #78.. Schematic Diagram of the Mini-ASTROD Spacecraft: Cylindrical spacecraft with diameter 2.5m, height 2m and surface covered with solar panels, (ii) In orbit, the cylindrical axis is perpendicular to the orbit plane with the telescope pointing toward the ground laser station. The effective area to receive sunlight is about 5m2 and can generate over 500W of power. (iii) The total mass of spacecraft is 300-350 kg. That of payload is 100-120 kg. (iv) Science data rate is 500 bps. The telemetry rate is 5 kbps for about 9 hours in two days. Both ASTROD and LISA respond to solar oscillations. The time constants for solar oscillations are long --- over 106 yr for low-l g-mode oscillations and over 2-3 months for low-l p-mode oscillations. The distance to the Sun of the inner ASTROD spacecraft varies from 0.77 AU to 1 AU and that of the outer ASTROD spacecraft varies from 1 AU to 1.32 AU. When the spacecraft move in solar orbits, the amplitude and direction of the solar oscillation signals receive deep modulations in addition to the modulations due to spacecraft motion and orientation. The time constant for the gravitational radiation (or orbit evolution) of the close white dwarf binaries (CWDB) is more than 106 yr, and hence the CWDB confusion background is steady in the inertial space. This background is modulated only by the orientations and motions of spacecraft, not by the distances and orientations of the spacecraft relative to the Sun. With this extra modulation --- deep in magnitude and direction, the detectability of the solar oscillation signals (hence the separability with G-waves) reaches at least 5 orders lower than the confusion limit in energy, i.e., to the instrumental noise floor. Imperial College Henrique Araújo Diana Shaul Timothy Sumner CERGA J-F Mangin Étienne Samain ONERA Pierre Touboul Max-Planck, Gårching Albrecht Rüdiger Technical U, Dresden Sergei Klioner Soffel IAA, RAS George Krasinsky Elena Pitjeva ZARM, Bremen Hansjörg Dittus Claus Lämmerzahl Stephan Theil Humboldt U, Berlin Achim Peters U Düsseldorf Stephan Schiller Andreas Wicht Purple Mountain Obs, CAS Wei-Tou Ni A. Pulido Patón J. Shi C.-F. Tong F. Wang Y. Xia Jun Yan Nanjing N U, X. Wu, C. Xu Huazhong S & T U Ze-Bing Zhou  Purple Mountain Obs, CAS Gang Bao Guangyu Li Lei Liu H-Y Li Yunnan Obs, NAOC, CAS Y.Xiong ITP, CAS, Y-Z Zhang U Missouri-Columbia Sergei Kopeikin Nanyang U, Singapore H-C Yeh Nanjing U Tianyi Huang IP, CAS Y-X Nie Z. Wei Tsing Hua U Sachie Shiomi Nanjing A & A U H. Wang ASTROD ASTROD I Christensen-Daalsgard (2002) Welcome to the 3rd ASTROD Symposium Beijing, July 16-23, 2006 (1st, Beijing, Sept. 21-23, 2001; 2nd, Bremen, June 2-3, 2004) wtni@pmo.ac.cn 6th Edoardo Amaldi Conference on gravitational waves, June 20-24, 2005 Bankoku Shinryoukan, Kise Nago See also Poster #66 See Poster #1