Transcript Mini-ASTROD: Mission Concept

ASTROD and ASTROD I: DeepSpace Laser Ranging Missions
ASTROD: ASTRODYNAMICAL SPACE
TEST OF RELATIVITY USING
OPTICAL DEVICES
ASTROD I --- A FIRST STEP OF
ASTRODYNAMICAL SPACE TEST OF
RELATIVITY USING OPTICAL
DEVICES
presented by Wei-Tou Ni, Purple Mountain Observatory,
Chinese Academy of Sciences, Nanjing
1
Current ASTROD Collaborators
ZARM, Bremen
Hansjörg Dittus
Claus Lämmerzahl
Stephan Theil
Imperial College
Henrique Araújo
Diana Shaul
Timothy Sumner
CERGA
J-F Mangin
Étienne Samain
ONERA
Pierre Touboul
Humboldt U, Berlin
Achim Peters
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Purple Mountain Obs, CAS
U Düsseldorf
Wei-Tou Ni, Gang Bao,
Stephan Schiller
Guangyu Li, H-Y Li,
Andreas Wicht
Max-Planck, Gårching A. Pulido Patón, J. Shi,
F. Wang, Y. Xia, Jun Yan
Albrecht Rüdiger
Technical U, Dresden CAST, Li Wang, Hou,
Zhang, ...
Sergei Klioner
IP, CAS, Y-X Nie, Z. Wei
Soffel
U Missouri-Columbia Yunnan Obs, CAS, Y.Xiong
ITP, CAS, Y-Z Zhang
Sergei Kopeikin
Nanjing U Tianyi Huang
IAA, RAS
George Krasinsky Tsing Hua U Sachie Shiomi
Nanjing A & A U H. Wang
Elena Pitjeva
Nanyang U, Singapore Nanjing N U, X. Wu, C. Xu
H S & T U, Ze-Bing Zhou
H-C Yeh
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ASTRODynamical Space Test of
Relativity using Optical Devices
S/C 2
S/C 1
Laser Ranging
Launch Position
Inner Orbit
Sun
Outer Orbit
Earth Orbit
point
.EarthL1(800
days after launch)
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OBJECTIVE
ASTROD

Testing relativistic gravity and the fundamental
laws of spacetime with 5 order-of-magnitude
improvement in sensitivity;
 Improving the sensitivity in the 5 µHz - 5 mHz low
frequency gravitational-wave detection by several
orders of magnitude as in LISA but shifted toward
lower frequencies;
 Revolutionize the astrodynamics with laser ranging
in the solar system, increasing the sensitivity of
solar, planetary and asteroid parameter
determination by 3-4 orders of magnitude.
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ASTROD I: Two-Way Interferometric and
Pulse Laser Ranging between
Spacecraft and Ground Laser Station
0.8


Testing relativistic gravity with 3-order-ofmagnitude improvement in sensitivity;
Astrodynamics & solar-system parameter
determination improved by 1-3 orders of
magnitude;
Improving gravitational-wave detection compared
to radio Doppler tracking (Auxiliary goal).
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(B)
0.6
0.4
0.2
Y Axis (AU)

0.0
Sun
-0.2
-0.4
-0.6
-0.8
Venus
Mercury
spacecraft
-1.0
-0.8 -0.6 -0.4 -0.2
0.0
0.2
0.4
ASTROD study team
X axis (AU) 5
0.6
0.8
1.0





1993 Laser Astrodynamics was proposed to study the
relativistic gravity and to explore the solar system in 2nd
William Fairbank Conference (Hong Kong) and in the
International workshop on Gravitation and Fifth Force
(Seoul).
ASTROD mission concept – 7th Marcel Grossmann
(Stanford, 1994) and 31st COSPAR (Birmingham, 1996)
Ġ /G and solar-system mass loss measurement
(Seoul, 1996)
G-wave sensitivity studied; Mini-ASTROD and
Super-ASTROD proposed (1st TAMA Meeting,
Tokyo, 1997)
Lab and Mission Concept Studies (1993-2000)
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International Collaboration Period

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
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


2000: ASTROD proposal submitted to ESA F2/F3 call (2000)
2001: 1st International ASTROD School and Symposium held
in Beijing; Mini-ASTROD study began
2002: Mini-ASTROD (ASTROD I) workshop, Nanjing
2004: German proposal for a German-China ASTROD study
collaboration approved
2005: 2nd International ASTROD Symposium of these
combined meetings (June 2-3, Bremen, Germany)
2004-2005: ESA-China Space Workshops (1st &2nd,
Noordwijk & Shanghai), potential collaboration discussed
2006: Collaboration Proposal Applied to Sino-German Center;
3rd ASTROD Symposium (July 14-16, Beijing) before
COSPAR (July 16-23) in Beijing
May- September, 2006: Joint ASTROD I proposal to be
submitted to ESA call for Cosmic Vision proposals
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Gravitational wave strain sensitivity
for ASTROD compared to LISA
1E-15
LISA Bender extension
LISA, 1 yr int. time S/N=5
1E-16
Gravitational Wave Strain
ASTROD, 1 yr int. time, S/N=5
1E-17
1E-18
1E-19
1E-20
1E-21
1E-22
1E-23
1E-24
1E-25
1.00E-06
1.00E-05
1.00E-04
1.00E-03
1.00E-02
1.00E-01
Frequency (Hz)
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Outgoing Laser beam
Telescope
Optical readout
beam
Incoming Laser
beam
Dummy telescope
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Proof mass
Large gap
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Orbit Simulation Assumptions

(1) The uncertainty due to the imprecision of the
ranging devices:
1 ps one way (Gaussian)
 (2) Unknown acceleration due to the imperfections
of the spacecraft drag-free system:
10-17m/s2 & change direction randomly
every 4 hr (~104s)
[This is equivalent to (10-17m/s2)  (104s)1/2
= 10-15m/s2(Hz) ½ at 10-4Hz]
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Error (s)
An error simulation for 2015
launching orbit
2.0x10
-11
1.5x10
-11
1.0x10
-11
5.0x10
-12
Outer
0.0
-5.0x10
-12
-1.0x10
-11
-1.5x10
-11
-2.0x10
-11
-2.5x10
-11
0
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500
1000
1500
2000
Time (day)
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2500
3000
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Gaussian Fits & Propagation of
Errors
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Simulation for 3000 days
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Expected Mass-Loss Rate
of the Sun
Mechanism
Fractional Rate
-------------------------------------------------Solar EM Radiation
7 Х 10-14/yr
Solar Wind
~ 10-14/yr
Solar Neutrino
~ 2Х 10-15/yr
Solar Axion
~ 10-15/yr
-------------------------------------------------2006.04. 21.
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Aimed accuracy of PPN space parameter γ for
various ongoing / proposed experiments.
The types of experiments are given in the parentheses.
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Crucial Technology
 100
fW weaklight phase locking
 Design and development of
sunlight shield system
 Design and development of dragfree system
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The Results for
20 pW Power Beam
Error
Signal
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X: 20 s/div
Y: 10 mV/div
Locked
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X: 50 ms/div
Y: 10 mV/div
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Experemental Results
Low Power Beam Intensity
(measured using oscilloscope)
High Power Beam Intensity (mW)
Low Power Intensity Measured
by Lock-in Amplifier
r.m.s. Error signal Vrms（mV ）
r.m.s Phase error（rad）
Phase-locking time
20 nW
2 nW
200
pW
20 pW
2
pW
2
2
0.2
0.2
0.2
153
~247
pW
N/A
N/A
20.9 nW 2.15 nW
2.01
2.06
2.29
2.03
2.70
0.0286
0.057
0.2
0.16
0.29
Longer than
observation
duration
Longer
than
observation
duration
>2
hours
>2
hours
1.5
presented by Wei-Tou Ni, Purple Mountain Observatory,
Chinese Academy of Sciences, Nanjing
mins
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Weaklight Phase Locking





Requirement: phase locking to 100 fW weak light
Achieved: phase locking of 2 pW weak light with 200 µW
local oscillator
With pre-stabilization of lasers, improving on the balanced
photodetection and lowering of the electronic circuit noise,
the intensity goal should be readily be achieved
This part of challenge should be focussed on offset phase
locking, frequency-tracking and modulation-demodulation
to make it mature experimental technique (also important
for deep space communication)
Weak light phase locking experiment re-started at PMO
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Drag-free System R & D

Consists of a high-precision accelerometer/inertial
sensor to detect non-drag-free motions and microthruster system to do the feedback to keep the
spacecraft drag-free
 Looking for collaboration with ONERA and
Trento University to learn the R & D they have for
accelerometer/inertial sensor
 Collaboration with ZARM, Bremen University for
feedback control and end-to-end spacecraft model
 Collaboration with Imperial College on charge
control of the proof mass
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Design of Sunlight Shield System
Sun shutter
Narrow band filter
FADOF filter
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Design of Sunlight Shield System

The sunlight shield system consists of a
narrow-band interference filter, a FADOF
(Faraday Anomalous Dispersion Optical Filter)
filter, and a shutter
 The narrow-band interference filter reflects
most of the Sun light directly to space
 The bandwidth of the FADOF filter can be 0.65 GHz
 With the shutter, the Sun light should be less
than 1 % of the laser light at the photodetector
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Solar
oscillation
modes
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BISON
network
observations
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μ
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 1-year
amplitude modulation of solar
oscillation for ASTROD
 A joint/dedicated mission are under
investigation
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ASTROD GOAL




Testing relativistic gravity and the fundamental
laws of spacetime with 5 order-of-magnitude
improvement in sensitivity;
Improving the sensitivity in the 5 µHz - 5 mHz low
frequency gravitational-wave detection by several
orders of magnitude as in LISA but shifted toward
lower frequencies;
Revolutionize the astrodynamics with laser ranging
in the solar system, increasing the sensitivity of solar,
planetary and asteroid parameter determination by
3-4 orders of magnitude.
Chance to detect solar g-mode oscillations
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ASTROD I
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ASTROD I: Two-Way Interferometric and
Pulse Laser Ranging between
Spacecraft and Ground Laser Station
0.8


Testing relativistic gravity with 3-order-ofmagnitude improvement in sensitivity;
Astrodynamics & solar-system parameter
determination improved by 1-3 orders of
magnitude;
Improving gravitational-wave detection compared
to radio Doppler tracking (Auxiliary goal).
2006.04. 21.
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(B)
0.6
0.4
0.2
Y Axis (AU)

0.0
Sun
-0.2
-0.4
-0.6
-0.8
Venus
Mercury
spacecraft
-1.0
-0.8 -0.6 -0.4 -0.2
0.0
0.2
0.4
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X axis (AU) 32
0.6
0.8
1.0
Typical Launch Trajectory of
ASTROD I
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Spacecraft Trajectory
0.8
(B)
0.6
0.4
Y Axis (AU)
0.2
0.0
Sun
-0.2
-0.4
-0.6
-0.8
Venus
Mercury
spacecraft
-1.0
-0.8 -0.6 -0.4 -0.2
0.0
0.2
0.4
0.6
0.8
1.0
X axis (AU)
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Spacecraft-Venus Distance
1.6
(B)
Distance between
spacecraft and Venus
1.4
Distance (AU)
1.2
1.0
0.8
0.6
0.4
0.2
0.0
(111.75 day, 34904.2 km)
-0.2
0
200
(336.24 day, 24640.6 km)
400
600
800
Mission Day
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Orbit Description

Launch via low earth transfer orbit to solar orbit
with orbit period 300 days
 First encounter with Venus at 118 days after
launch; orbit period changed to 225 days
(Venus orbit period)
 Second encounter with Venus at 336 days after
launch; orbit period changed to 165 days
 Opposition to the Sun: shortly after 370 days,
718 days and 1066 days
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Apparent Angles during 2 Solar Oppositions
0.4
0.3
0.2
0.1
Angle Z (Deg)
0.0
Sun
-0.1
-0.2
719.7 day
717.1 day
-0.3
-0.4
369.1 day
371.3 day
-0.5
-0.6
-0.7
-0.8
-0.6
1st closest approach
nd
2 closest approach
o
0.377 (1.51R¡ó )@ 370.2 day
0.315 (1.26R¡ó )@ 718.4 day
o
-0.4
-0.2
0.0
0.2
0.4
0.6
Angle Y (Deg)
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Shapiro Time Delays
Shapiro Time Delay (£gsec)
120
111.4 £gsec
107.2 £gsec
100
80
60
40
20
0
0
200
400
600
800
Mission Day
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Orbit Simulation Assumptions

(1) The uncertainty due to the imprecision of the
ranging devices:
10 ps one way (Gaussian)
 (2) Unknown acceleration due to the imperfections
of the spacecraft drag-free system:
10-15m/s2 & change direction randomly
every 4 hr (~104s)
[This is equivalent to (10-15m/s2)  (104s)1/2
= 10-13m/s2(Hz) ½ at 10-4Hz]
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3 Sets of
Simulated
Data
(Total: 50
sets)
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Uncertainties of Determining Gamma
and Beta as a function of Epoch
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Uncertainties of Determining Solar
Quadrupole Parameter J2 as a function of
Epoch
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Gaussian Fit of 50 Determinations
of Relativistic Parameters
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Orbit Simulation Results
 Determine
the relativistic parameter
γ to 10-7.
 Determine the relativistic parameter
β to 10-7 and others with improvement.
 Improve the solar quadrupole moment
parameter J2 determination by one
order of magnitude, i.e., to 10-9.
 Ġ /G to 10-13/yr
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Schematic Diagram
of the ASTROD I Spacecraft
Black Surface
FEEP
Power Unit
Optical
Comb
Clock
CW Lasers
Optical
Cavity
Thermal Control
Electronics
Telescope
TIPO
Pulse Laser
Power Unit
Black Surface
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FEEP
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Schematic Diagram of the
ASTROD I Spacecraft:

(i) Cylindrical spacecraft with diameter 2.5m, height
2m and cylindrical 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 500 W
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.
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Payload
(1) Laser systems for interferometric and pulse ranging
(i) 2 (plus 1 spare) diode-pumped Nd:YAG laser
(wavelength 1.064 m, output power 1 W) with a
Fabry-Perot reference cavity: 1 laser locked to the
Fabry-Perot cavity, the other laser pre-stabilized by
this laser and phase-locked to the incoming weak light.
(ii) 1 (plus 1 spare) pulsed Nd:YAG laser with
transponding system for transponding back the
incoming laser pulse from ground laser stations.
(2) Quadrant photodiode detector
(3) 380-500 mm diameter f/1 Cassegrain telescope
(transmit/receive), /10 outgoing wavefront quality
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Payload
(4) Sunlight Shield System
(5) Drag-free proof mass (reference mirror can be
separate):
50  35  35 mm3 rectangular parallelepiped;
Au-Pt alloy of extremely low magnetic suceptibility
(<10-5);
Ti-housing at vacuum 10-5 Pa ; six-degree-offreedom capacity sensing.
(6) Cesium clock
(7) Optical comb
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One Way Laser ranging
Time Transfer by Laser Link
TIPO
Etienne Samain, Patrick Vrancken
OCA, Gemini
2130 route de l’Observatoire
06460 Caussols, FRANCE
Philippe Guillemot
CNES
Av Edouard Belin
31400 Toulouse, FRANCE
Cheng Zhou (PMO) is in OCA studying and
working on 3 ps event timer
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Ground Station for the ASTROD I
Mission at Yunnan Observatory
◆ Introduction of Yunnan Observatory 1.2m Telescope
＆ Its Laser Ranging System
◆ Key Requirements of Ground Station for the Mission
◆ Telescope Requirement: Pointing and Tracking Accuracy
◆ Atmospheric Turbulence Effects on Laser Ranging
◆ F. Song of Yunnan Observatory is collaborating with Y. Luo
of PMO to study the laser acquisition and pointahead
presented by Wei-Tou Ni, Purple Mountain Observatory,
Chinese Academy of Sciences, Nanjing
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◆
Yunnan Observatory 1.2 mTelescope
 Its Laser Ranging System
Coordinates:
Latitude
25.0299  N
Longitude
102. 7972  E
Elevation
1991.83 m
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Optics Design for ASTROD I

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Albrecht Ruediger and Haitao Wang :
Bremen talk 2005, and ASTROD2006 talk
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ASTROD I Drag-free Control

Hongying Li from PMO is in Bremen
studying and working with Stephan Theil,
Hansjoerg Dittus, and Claus Laemmerzahl
to work out a preliminary drag-free control
for ASTROD I.

Paper to be presented in the forthcoming
COSPAR general assembly.
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2006.04. 21.
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Theoretical Foundations

Chongming Xu: 2nd order light deflection
 Kopeikin, Klioner, Soffel
 Tianyi Huang: time scales
 Peng Dong, Yi Xie: 2nd order Post-Newtonian
Approximation and Astrodynamics
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Acceleration disturbances and
requirements for ASTROD I
Sachie Shiomi and Wei-Tou Ni
Center for Gravitation and Cosmology
Dept. of Phys., Tsing-Hua Univ., Hsinchu
presented by Wei-Tou Ni, Purple Mountain Observatory,
Chinese Academy of Sciences, Nanjing
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ASTROD I:
Charging Simulation & Disturbances
Gang Bao(1,2), Diana N A Shaul(3), Henrique M Araujo(3), Wei-Tou Ni(1,2),
Tim J Sumner(3) & Lei Liu(1)
(1)Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008
(2)National Astronomical Observatories, Chinese Academy of Sciences, Beijing
100012
(3)Department of Physics, Imperial College London, London, SW7 2BZ, UK
2nd
presented by Wei-Tou Ni, Purple Mountain Observatory,
Chinese Academy of Sciences, Nanjing
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International ASTROD Symposium, 2-3 June 2005, ZARM, Bremen, Germany
GEANT4 Charging Simulation
Charging for Protons
Q(t) = 26.2 +e/s
180
160
Charge(+e)
140
120
100
80
60
40
20
0
-20 0
2
4
6
8
Time(s)
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Launcher and Mission Lifetime

Launcher: Long March IV B (CZ-4B)

Mission Lifetime:
3 years (nominal)
8 years (extended)
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OUTLOOK
ASTROD I




Testing relativistic gravity and the fundamental laws
of spacetime with three-order-of-magnitude
improvement in sensitivity; gamma to 10-7 or better,
beta to 10-7, J2 to 10-9, asteroid masses to 10-3 fraction
Improving the sensitivity in the 5 µHz - 5 mHz low
frequency gravitational-wave detection by several
times;
Initiating the revolution of astrodynamics with laser
ranging in the solar system, increasing the sensitivity
of solar, planetary and asteroid parameter
determination by 1-3 orders of magnitude.
Optimistic date of launch: 2015
2006.04. 21.
ASTROD & ASTROD I: Deep-Space Laser Ranging Missions
ASTROD study team
63
Spacecraft and Mission Analysis
Study

2006.04. 21.
Li Wang, Hou, Zhang, ... from China
Academy of Space Technology are working
on it
ASTROD & ASTROD I: Deep-Space Laser Ranging Missions
ASTROD study team
64
Thank you!
2006.04. 21.
ASTROD & ASTROD I: Deep-Space Laser Ranging Missions
ASTROD study team
65