Post on 09-Dec-2018
Status of the ESA Feasibility Study
HYPER
Ulrich Johann
Astrium GmbH
(for the industrial team)
CNES, Paris
5.11.2002Ulrich.johann@astrium-space.com
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
Presentation outline:Scientific Objective of the HYPER MissionThe present HYPER Mission Baseline The HYPER Feasibility Study
The Lense-Thirring Effect and HYPERHYPER Measurement Principle and Payload Definition
HYPER Technical Requirements Classification Orbit Selection Trade-offPayload Configuration Trade-off Atomic Sagnac Unit Conceptual Design PST Conceptual Design HYPER Payload Module Design
The HYPER DFAC Simulator Model Drag-free and Attitude Control (2.AOCS) Design (incl. IS, FEEP technology)
Summary and conclusions (status, remaining work, mission road map outlook)© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002 HYPER scientific mission objectives
•Mapping the spatial structure of the general relativistic gravito-magnetic effect of the Earth with better than 10% accuracy•Independent determination of the fine structure constant to test quantum-electrodynamics theories•Investigation of quantum de-coherence to set an upper bound for quantum gravity models•Demonstration of the superior performance of cold atom sensors for spacecraft control
Technical implications
To fully develop this potential, however, it is necessary to: • establish the operational environment for atom interferometry by proper spacecraft and payload engineering, namely:• drag-free control and supreme inherent stability of payload elements and pointing performance.
While the second and third science objective take advantage of the space environment only, the measurement of the Lense-Thirring effect necessitates a low earth orbit.
HYPER will also pursue the development of atom interferometry as a high precision sensor for spacecraft control in the future, driving the design towards compactness and robustness.
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002 HYPER Mission Baseline; June 2002
767.4 kg (Launcher capability 870 kg to 700 km)
Primary AOCS + secondary AOCS using Payload Module sensors for error generation during Science Mode (drag-free control and fine pointing) 16 x 500 µN FEEP thrusters + 8 x 40 mN cold-gas thrusters
499 W (EOL) Fixed 3.3 m2 GaAs solar array + 6 Ah Li-ion battery
S-band, 500 kbps during 7-minute passes, total of 190 Mbit/day 15 m-antenna at the ESA Kiruna station, Mission Control ESOC
Spacecraft launch mass:
AOCS:
Propulsion:
Power:
Telemetry:Ground segment:
Dawn-dusk, Sun-synchronous orbit at 700 km altitude, 98.2° inclination, 98.6 minLow-cost Rockot launch vehicle from Plesetsk CosmodromeTo be based on road map results (in terms of technical readiness, 2009)2 years (nominal)
Orbit:Launcher:Launch year:Mission lifetime:
247.5 kg203 W937 mm diameter x 1300 mm height
Optical elements for coherent atom manipulationHigh-precision star tracker (200 mm ∅ Cassegrain Telescope, pointing
performance, 10 Hz readout frequency)2 drag-free proof masses (asymmetric arrangement)
4 atom interferometers based on caesium or rubidium accommodated in 2 magnetically shielded vacuum chambers Optics for atom preparation and detection
Lasers for atom interferometry (Raman), preparation and detection of the atomsHigh-precision µW synthesiser for the hyperfine transitions of caesium or rubidium
Payload Mass:Payload Power:Payload Dimensions:
Optical Bench:
Atom Preparation Bench:(not a detailed subject of this study)
Laser Bench:(not subject of this study)
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002 The HYPER Feasibility Study
Study overview
•ESA/ESTEC Invitation to tender February 2002 •Proposal March 2002
•Study Kick off June 6th, 2002•Intended study duration: 6 months•Final presentation planned for February, 2003
•Study team:Astrium Germany, Astrium UK, Galileo Avionica, Zarm
•The principle feasibility of the HYPER mission has been assessed in the ESA internal CDF study, which is also the starting point for this industrial feasibility study.
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
Main Study Activities
The HYPER Feasibility Study
•Central to this study is the demonstration of system performance by detailed design and analysis, supported by a simulation in particular for drag-free control, precision pointing and thermo-elastic stability of payload elements.
•Further, a road map for HYPER, taking into account on-going developments in related projects will be defined.
•The state of art for key components are being assessed and necessary upgrades to meet HYPER needs are identified.
•Specific ground verification needs will be assessed.
Only the measurement of the Lense-Thirring effect and the potential for using the atomic gyroscope as a precision AOCS sensor are setting the requirements for this study.
The Atomic Sagnac Unit (ASU) itself, a Mach-Zehnder type interferometer, is the core instrument for both study targets. (Complemented by an integrated Ramsey-Bordéinterferometer for the other science objectives.)
The detailed design and engineering for the interferometer itself as well as for the supporting laser bench is not subject of this study.
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
Study team and task allocation
The HYPER Feasibility Study
Customer : ESA/ESTEC (G.Bagnasco, P. Airey)
Science team: Consulting (E.Rasel, A. Landragin, P. Bouyer, M.Caldwell)
Industrial team:Astrium Germany Prime, system performance and engineering, AOCS
simulator and design, subsystems, AIVT, roadmap, Smart2 LTP optical bench heritage(U. Johann, W. Fichter, L. Szerdahelyi, H. Stockburger, B. Schürenberg)
Astrium UK AOCS environment and disturbance; orbit selection; Step, Smart2 platform consulting(S. Kemble, P.Chapman, N. Dunbar)
Zarm AOCS estimator and DFC sensor assessment(S.Theil, A.Schleicher, Silvia Scheithauer)
Galileo Avionica Optical payload engineering (OB and PST) (G. Cherubini, S. Becucci, A. Romoli)
(Alta FEEP consulting)
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
Analysis of SOW
payload requirements Review of present baseline
mission and engineering concepts
Environmental and internal disturbance sources characterization
Identification of critical areas and design
Clarification of open issues and possible trade-off envelopes
Reference mission, system concept , architecture and technology definition
System performance analysis and simulator
development
Optical payload
engineering
Critical subsystems assessment
Satellite configuration and subsystemsre-assessment based on payload analysis
and simulation results
Updating from related studies (Smart2,
Optimization and performance demonstration (re-fined simulation results)
Assessment ASU as
AOCS sensor
AIVT and specific on-ground testing and verification
Orbit selection and ti i ti
HYPER mission roadmap
Study logic flow
Dec. 2002
End of Jan. 2003
The HYPER Feasibility Study
6.6.2002
We are here
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
Study Work Breakdown Structure
The HYPER Feasibility Study
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002 The Lense Thirring Effect and HYPER
N
Ωx (ASU 3,4)
θ
Reey
ex
Ie ωe
Rox
yvo Ωy (ASU 1,2)
Ω EquatorMe
S
Ω Pole
Sun
Main disturbance:•Gravity gradients•Air drag•Thermal radiation
HYPER orbit geometry( begin of study)
•Sun synchronous•Dawn - dusk•700 km circular •Re = 6371 km•Inclination 90° + 8.2°•Period 98.6 min
view
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002 The Lense Thirring Effect and HYPER
equatorpoleR
otat
ion
[rate
rad/
s]
time [s]
Ωy parallel earth spin axisin orbit plane
Ωxperpendicular earth spin axis in orbit plane
© Astrium
The Lense-Thirring effect as function of time over two orbit periods.•The periodic cycle is half the orbit period.
•The geodetic de Sitter effect is 40 to 80 times bigger, but rotates perpendicular to orbit plane and is constant for circular orbits
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002 The Lense Thirring Effect and HYPER
The magnitude of the Lense-Thirring effect (in 10-14 rad/s) with varying orbit hight, latitude for polar orbit, 90 deg inclination
0
0.5
1
1.5
2
2.5
h=500
h=700
h=1000
h=1200
90 deg latitude
0 deg latitude
2E-142.1E-14
2.2E-142.3E-14
2.4E-142.5E-14
2.6E-142.7E-14
2.8E-14
500 600 700 800 900 1000 1100 1200 1300
Altitude (km)
Max
LT
effe
ct (r
ad/s
)
© Astrium
Illustration of the frame dragging effect(fictive black hole of sun mass and angular momentum)
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
y
x
2L
RbΩrot
Aacc
λ =780 nm
Tdrift
vT
vL
pT=2h/ λ
vT·Tdrift/2
Principles and geometry of the basic Atomic Mach-Zehnder Interferometer
•The device is sensitive to linear accelerations and rotations in the interferometer plane. •Two in-plane counter-propagating Mach Zehnder Interferometers are forming one ASU (Atomic Sagnac unit).•Their signals are subtracted to extract the rotation rate signal.
Detection
MOT
The HYPER Measurement Principle and Payload Definition
Preparation
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
The HYPER Measurement Principle and Payload Definition
Some ASU parameter values assumed
6.65·107·Aacc [m/s2]7.250·107·Aacc [m/s2]Фacc [rad]1.331·107· Ω [rad/s]1.450·107· Ω [rad/s]Фrot [rad]
600 mm x 11 mm600 mm x 18.7 mmSize of ASU active zone
0.0073 m/s0.0125 m/svt32.9 cm256.2 cm2A1.56·10-27 kg·m/s1.7·10-27 kg·m/sPt13385m (atomic units)2.13·10-25 kg1.36·10-25 kgM7.392·106 rad/m8.055·106 rad/mKγ850 nm780 nmLaser wavelength λ
CesiumRubidiumASU Parameter
2L = 600 mm, Tdrift = 3 s
© Astrium
Xk Yk, Zk,( )
PST line of sight
local reference: ASU in-plane rotation rate
Equatorial plane frame dragging measured by HYPER•The local inertial frame is probed by the ASU rotation rate measurement•The frame rotation is referenced to the global frame by distant star pointing measurement
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
The HYPER Measurement Principle and Payload Definition
global reference: guide star position
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
The HYPER Measurement Principle and Payload Definition
Aacc(z)
Ωrot(z)
Ωrot(y)
Aacc(y)
1 Precision Star Tracker
Optical Bench Structure
ASU 1,2
ASU 3,4View
Normal to orbit plane
2 Inertial Sensors
Aacc(x,y,z)Ωrot(x,y,z)
The HYPER payload optical bench as an assembly of attitude and acceleration sensors.•The two ASU groups ASU1,2 and ASU3,4 (counter-propagating Mach Zehnder Interferometers)•The Precision Star Tracker (PST)•The two Inertial Sensors (IS)
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
unambiguous range
The HYPER Measurement Principle and Payload Definition
tune ASU phase set point for in-space calibration and to stay within control range despite gravity gradients (e.g. by laser shirp between interaction regions)
control range to be maintained by drag-free and attitude control (DFAC)
Rotation rate, linear acceleration, gravity gradients,......
ASU signal intensity defined as the difference of two counter-propagating Sagnac units.The signals are illustrating coherence range, un-ambiguity range, linear regime and sensitivity (slope). The high frequency signal (red) stands for the nominal high sensitivity mode (3s drift time)and the low frequency signal (blue) for a fast lower sensitivity mode (AOCS sensor mode; 1s drift time).
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
Disturbances and sensors for science objectives and drag-free and attitude control
The HYPER Measurement Principle and Payload Definition
Attitude projection effects
ASU PSTISLense-
Thirring Guide Star
External noise:•Gravity gradients
•Drag
•Thermal fields
•Charging
•Magnetic field
•Thruster noise
Measures:
Rot, Acc within two ortogonal sensitve planes10-12 rad/s10-13 m/s2
Bandwidth
0. 001 -0.3 Hz
Measures:Rot, AccAll directions10-7 rad/√Hz100 pm/√Hz10-14 m/s2/√HzBandwidth lowHigh possible
Measures:
Rot
Lateral to line of sight 10-7 rad/10Hz
Bandwidth medium depends on star magnitude
Abberations:•Refraction
•Special relativity
•General reativity (light bending by frame dragging)
•Star proper motion
•Coordinate system transformations from moving S/C to star
•Extended object
Transfer budgets Transfer budgetsDe Sitter
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
The HYPER Measurement Principle and Payload Definition
AtomInterfero-
meter
InternalASU phasecorrection
compensationof gravity gradient
acceleration
gravity gradientacceleration
Drag-free andattitude control
spacecraft
GG estimate
GG
rC,A estimate
rC,A
Other effects(magnetic, self gravity,thermo-elastic motion)
a, ω, dω/dt
aGG
phaselaser
frequency
disturbance(drag, etc.)
aGG estimate
low frequency “servo” loopEffects on the ASU phase shift
knowledge 10-11
•The ASU needs to be isolated from external and spacecraft disturbance by the DFAC (drag-free and attitude control) and precision thermal control (supported by design)
•The ASU signal itself is used in feedback to stay within control range© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
geopotentialmodel
geopotentialpos. knowledge
geopotentialatt. knowledge
self gravity
gravity gradientknowledge
magneticenvironment
temperature
timing/jitter
radiation
alignment(set of reqs.)
ASUmeasurement
accuracy
PST/OBalignment
OB/RRMalignment
PST/OBalignmentstability
OB/RRMalignmentstability
ASU-PSTalignment& stability
PST internal bias andlow frequency accuracy
PST thermalmisalignment
star catalogueaccuracy
aberration effects
arithmetic
electronicand shot noise
timing/jitter
PSTmeasurement
accuracy
acceleration@ drag-free point
acceleration fromangular motion
acceleration fromthermo-elastic motion
linear accelerationdynamic range
rotation ofrigid body
rotation fromthermo-elastic motion
ratedynamic range
alignmentRRM/FI
alignmentRRM/AA
grav. grad. knowledge(for compensation)
ASUoperationalenvelope
LT measurementaccuracy
2.5e-15 rad/sec
LevelLevel--00
HYPER Technical Requirements Classification
Requirements breakdown
LevelLevel--11
LevelLevel--22
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
HYPER Technical Requirements Classification
Level-0 Requirements (1)
• Approach: “equal” distribution between ASU measurement accuracy and PST measurement accuracy
• ASU-PST alignment stability to be negligible
1/10 Lense-Thirring frequency
© Astrium
• “High pass” filtering effect due to data processing
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
HYPER Technical Requirements Classification
Level-0 Requirements (2)
• ASU Measurement Accuracy– one sample accuracy 5.0 10-12 rad/sec (3sig) @ 0.3 Hz
1/10 Lense-Thirring frequency
• PST Measurement Accuracy– one sample accuracy:
1.2 10-8 rad (3sig) @ 10 Hz– relative gain according
to “high pass” filter
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
HYPER Technical Requirements Classification
Level-0 Requirements (3)
• ASU-PST Alignment Stability– zero frequency: better than 1 as– 3.5 10-5 Hz - 5 Hz: 1.75 10-9 rad/√Hz– less than 3.5 10-5 Hz: relative gain according to “high pass” filter
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
HYPER Technical Requirements Classification
Level-1 Requirements (1)
• Most critical ASU requirements (3σ):
– gravity gradient knowledge: 2.4 10-11 1/sec2 !!– displacement of mirror origin and optical path between
atoms and mirror <40pm over 3 sec– magnetic cleanliness requirements
• Most critical PST requirements (3σ):
– centroiding error smaller than 2 10-3 as
• Most critical operational envelope requirements (3σ):(technical driver for DFAC)
– residual acceleration < 1.7 10-8 m/sec2
– residual rate <4.3 10-8 rad/sec
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002 Orbit Selection Trade-off
Gravity gradient altitude dependence
• Gravity gradient in the order of 1 10-6 1/s/s– GG must be modelled, model fidelity depends on altitude– altitude 1000 km requires a
• 20th order GG model on ground (req. 2.4 10-11 1/s/s)• 2nd order model on board for envelope control (req. 3.4 10-8 1/s/s)
1.90E-06
2.00E-06
2.10E-06
2.20E-06
2.30E-06
2.40E-06
2.50E-06
2.60E-06
6700 6800 6900 7000 7100 7200 7300 7400 7500
Orbital altitude (km)
Grav
ity g
radi
ent (
/s/s
)
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002 Orbit Selection Trade-off
Gravity gradient spatial dependence
• Gravity gradient model fidelity: 2nd order (“model”) w.r.t. 10th order (“truth”)
0108
216
324
-80 -4
8 -16 16
4880
02E-114E-116E-118E-111E-101.2E-101.4E-10
Longitude (deg)
Lat
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002 Orbit Selection Trade-off
Further criteria for orbit altitude selection:
• Orbit Altitude 1000 km
– LT effect degraded– Smaller number of eclipse days
• reduces LT degradation (due to small LT magnitude)
– Total dose: no driving impact
– Rockot launch to 1000km Sun-synchronous orbit feasible
Lower orbit: increased external disturbance, gravity gradient modelling more complex
Higher orbit: launcher capability limits
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
Drag-free and Attitude Control (2.AOCS) Design
Disturbance Rejection Mechanisms for Interferometer Phase
slow drifts
ASU-measured
acceleration
© Astrium
ASU Sampling
Acc. noiseASU Phase
ControlDrag-Free
Control
Equivalent Phase @ ASU
residual acceleration
Disturbance rejection @ very low frequencies < typically 3.5 10-5 Hz(8 hours)
Disturbance rejection @ frequencies> 0.3 Hz (sampling frequency)
Disturbance rejection @ frequencies < control bandwidth (0.01 Hz)
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
Drag-free and Attitude Control (2.AOCS) Design
• Drag-Free and Attitude Control Loops
inertial position
DFS 1
PST
DFS 2
Payload sensors
GPSReceiver
To ASU for compensation
purposes
Estimatedgravity gradientGravity Gradient
Estimate
StarTracker
ThrusterSelection
Actuation signal for
each FEEP thruster
FEEPs
4 sets of4 FEEPs
each
© Astrium
X,Y,Z-AxisLinear Acceleration
Controller
X-AxisAttitude Controller
Y,Z-AxisAttitude
Controller
3-axis attitude
y/z-attitude
3-axis linear accelerations
x-axis attitude
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
Drag-free and Attitude Control (2.AOCS) Design
Noise rejection
10-4 10-3 10-2 10-1 100 10110-12
10-11
10-10
10-9
10-8
10-7
10-6
RequiredFEEPsAeroDistMaxAcceleration
– Drag noise relatively small– FEEP noise to be attenuated at low
frequencies– Relatively low closed loop
bandwidth sufficient (0.01Hz)
FEEP noise to be rejected by DFAC loop• Rejection of FEEP Noise and Air Drag Noise
– Main disturbances: FEEP noise and air-drag– Figure includes ASU filter effect
ASU sampling
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
Drag-free and Attitude Control (2.AOCS) Design
Micro-propulsion
21
Solar Array
24
23
22
313
414
122
11
1
YZ X
• Forces and Torque– max thrust typ. < 250 micro-N– driven by
• GG torque• CoM-DFP distance
• Thruster Configuration– total 16 thrusters– 4 sets of 4 thrusters
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
Drag-free and Attitude Control (2.AOCS) Design
Drag-free control aspects summary
– drag-free requirements are moderate (≈1 10-8 m/sec2/sqrt(Hz))
– drag-free control concept relies on low frequency phase control within ASU• allows “relaxed” DFS measurement requirement at low frequency• => use “existing” DFS
– measurement concept with 2 DFS`s• imposes configuration requirements• solution with minimum mass and power
– relatively low noise disturbances• air-drag (noise) is relatively small due to 1000 km orbit• => relatively low bandwidth of drag-free control sufficient, simplifies controller and
estimator design– maximum thrust 250 micro-N
– critical points are:• dependence on PST measurement accuracy - still to be finally clarified with
simulation• availability of FEEPs (GOCE FEEP specification sufficient)
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002 Payload Configuration Trade-off
Principal considerations:•The payload configuration and architecture has a large impact on spacecraft configuration, architecture and on DFAC performance and needs to be defined first.•The payload configuration is determined by the arrangement, size and budgets of accommodated sensors and by the stability requirements (internal transfer functions)• The payload configuration is determined by the ASU intrinsic requirements, concept, design and budgets
Three candidate concepts have been identified, driven by different requirement priorities:
1. Previous design concept (cdf report)• PST and mirror groups mounted to a common fiducial block (ULE)• 2 Inertial sensors in assymetric arrangement with respect to boresight of PST2. DFAC sensor envelope concept• PST and mirror groups mounted to a common fiducial block (ULE)• 3 or 4 inertial sensors defining envelope of DFC area arround ASU´s3. DFAC driven concept (selected as baseline)• Two inertial sensors in line with the intersection of ASU planes• The telescope is moved to a lateral position4. Integrated ASU fully symmetric concept• Both ASU planes are integrated into one atomic beam assembly• Telescope, ASU, 2 inertial sensors are in line
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002 Payload Configuration Trade-off
Optical Bench Configuration Option 1
Previous CDF baseline
• IRS axis tilted towards ASU axes (projection effects)• Virtual DFC point (AOCS reference) „close“ to ASU plane intersection• PST in front or inside fiducial block
y
xzOptical Bench Structure
ASU2
ASU1IRS1
IRS2
PST
COM
Virtual AOCSRef.
COM
ASU2
ASU1PST
IRS1COMVirtual
AOCSRef.
© Astrium
Optical Bench Configuration Option 2
Attractive optional concept studied
• direct measure of 3D gravity gradients by 3 or 4 IRS• direct measure of angular rotations on all axes• DFC virtual control point can be located arbitrarily• very compact architecture• PST and mirror block same fiducial frame• requires 3 or 4 IRS units and control and read out electronics
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002 Payload Configuration Trade-off
Optical Bench Structure
ASU2
IRS1 IRS2
PST
Virtual AOCSRef.
ASU2
ASU1PST
ASU1 Virtual AOCSRef.
y
xz
IRS3
IRS4
IRS1 IRS4
COM COM
Gravity gradients directly measured by IS´s (10-10 level) © Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002 Payload Configuration Trade-off
Optical Bench Configuration Option 3
Baseline concept selected in study
y
xzOptical Bench Structure
Virtual AOCSRef.
ASU2
ASU1IRS1 IRS2
PST
COM
Virtual AOCSRef.
ASU2
ASU1
PST
IRS
COM
• IRS axis , DFC reference and ASU plane intersection collinear• PST plate mounted , centered or using full length of bench• Thermo-elastic stability less favourable due to asymmetry
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002 Payload Configuration Trade-off
Optical Bench Configuration Option 3
Integrated 2-D ASU (advanced payload concept)
© Astrium
ASUxy
IRS1
IRS2
Virtual AOCSRef.
PST
COM
ASUzIFz 3
ASUYIFY 1
yx
Mirror framesz
counterpropagating atomic beam not shown
• sequential generation of two perpendicular MZ IF planes from one atomic beam (same or two subsequent clouds)• highly integrated, symmetric concept• requires switching of B-field collinear to active laser beams (sig pol) or B collinear to atomic beam axis (pi pol)• sequential detection• significant instrument development necessary• path towards integrated ASU sensor??
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002 ASU Conceptual design
Assumptions made on ASU internal specifications(impacting optical bench interfaces and accommodation)
Raman laser:
wavelength 852 nm pi pulse few µs diam. (80%) 60 mm intensity TBD W/cm2
freq. stability TBD
Average power <m W
Detuning capability to keep ASU in control range: TBD
Fiber launcher:
pol. maintaining fiber core 5 µm , NA =0.2 collimation optics diam 60 mm, feff = 130 mm QWPfolding mirror required
Atomic cloud:
Cs (132.9) 1 µKvtemp = 13.7 mm/s vdrift = 200 mm/s @RL1 = 12 mm dia @RL2 = 53 mm @RL3 = 95 mm
Possible fiber launcher geometry to be accommodated on optical bench for each Raman laser beam:
QWP
80% central intensity (truncated Gaussian beam)
60 mm diam.
200 mm TBC © Astrium
© Astrium
ASU physical envelopes•ASU, Raman laser and atomic beam geometry (TBC)
300mm
tube 200 mm(d) x 700 mm
RL1 RL2 RL3
Cs/Rb oven, MOT, beam preparation, detection:
300 x 300 x 250 mm3
MOT coupling optics
included
100 mm
100
mm
vacuum housingµ-metal shieldmagnetic guide field solenoid
B
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002 ASU Conceptual design
laser,window, mirror opt. diam. 60 mm
300mm
© Astrium
100 mm
100
mm
300mm 300mm
11 mm
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002 ASU Conceptual design
It appears necessary to actively change atomic beam position and attitude and interferometer overlap in space
Geometry of ASU beams and Mach-Zehnder Interferometers
RL2RL1 RL3
100 mm
100
mm
300mm 300mm
Common area
Optical path change by temperature fluctuations in window (acceleration)
Common mode acceleration
Relative in-plane displacement d of counterpropagating Mach-Zehnder Interferometers
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002 ASU Conceptual design
ASU performance degrading thermo-elastic distortions
Optical path change by differential temperature fluctuations of mirror substrates and support (differential acceleration of surfaces)
Tilt of mirror surface
Relative in-plane tilt of counterpropagating Mach-Zehnder Interferometers
Raman laser in-plane tilt and shift
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HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
HYPER Payload Conceptual Design
Payload module precision star trackerBaseline concept to meet resolution requirement 2.5 mas:
+- 15 as0.074 as100 ms
FOVPixel FOVIntegration time
512 x 51213 µm square 15 x 15 or 17 x 17
CCD detector•Pixel area•Pixels size•Tracking matrix
36 m190
Optical configuration•Ritchey-Chretien telescope•Effective focal length•Pupil diameter
36 m effective focal length folded into optical bench dimensions (700 mm)
CCD
Alternative concepts:Optical wavefront sensing: Hubble fine guidance sensorOptical fringes by co-phasing of four small telescopesGravity probe B concept (radiometry, pyramid split)
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HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
HYPER Payload Conceptual Design
Payload module (Option 3)
ASU beam preparation and detection units
PST opto-mechanics and detection
PSTbaffle
ASU drift tube housing
ASU fiber launcher inserts
Inertial sensor
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HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
HYPER Payload Conceptual Design
Optical bench structure (ULE or Zerodur)
Payload module (Option 3) Back view
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
HYPER Payload Conceptual Design
Payload module complete configuration (Option 3)Incl. Fiber injectors and baffle thermal shield
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
HYPER Payload Conceptual Design
Payload module optical bench structure (Option 3) Exploded view of optical bench structure (ULE or Zerodur; integrated by hydroxyl bonding technique)
ASU drift tube housing: the optical bench structure itself is the vacuum enclosure for the drift tube; the ASU MOT and detection units are to be mounted to the facets
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
HYPER Payload Conceptual Design
Payload module optical bench structure (Option 3)Exploded view of optical bench structure (ULE or Zerodur)
Mirror group
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
HYPER Payload Conceptual Design
Payload module alternative optical bench configuration (Option 2)
Inertial Sensor 1
Inertial Sensor 2
Inertial Sensor 3
Inertial Sensor 4
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
HYPER Payload Conceptual Design
Payload module thermal design (Option 3)Thermo-elastic distortions of optical bench (preliminary analysis; to be confirmed)
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
HYPER Payload Conceptual Design
Thermal radiation control concept
•S/C inertially fix attitude -> albedo field rotates at orbit frequency arround S/C axis (z)
•6 W heat gradient radiated to OB lateral surface, rotating at orbit frequency
•Thermal stability of PLM requires active control of PLM thermal background (variabe environment in S/C and external radiation field)
•Uniform thermal background provided by 8 heater mats attached to S/C cylinder structure. Control capability +-0.2 °C
•Temperature level slightly elevated or lowered wrt. PLM to buffer external variation(value TBD). PLM set point temperature 20°C (TBC). Low heater power required (<20W, TBC)
•Radiative loss to space via baffle minimised by quarz thermal shield in front of PST and additional heater mat wrapped arround the baffle to compensate variable sink temperature (and to control OB set point temperature and internal stationary gradients)
•Thermal loss through vacuum vent TBD
•Detailed thermal budget available after thermo-elastic sensitivity from FE model is determined
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
HYPER Payload Conceptual Design
The present PLM configuration has been accommodated on a S/C architecture based on the CDF layout
Impact:
•Increased central cylinder diameter and adapter cone
•Added struts
•Octagonal shape of S/C bus has thermal advantages (optional concept)
•Detailed total mass budget pending freezing of PLM baseline and budgets
© Astrium
HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002
HYPER Payload Conceptual Design
The present PLM is isostatically mounted to the central S/C cylinderElements:•Attachement points on optical bench basic structural plates
•No stress introduced to optical bench
•No launch locks required
•Launch loads 12g along axis and 5g laterally assumed
•PLM Mass 350 kg assumed
•Heat intake via struts less than 100 mW total (assuming actively controlled cylinder temperature)
•Strut elements CRFP (blue); Ti (red)
•Fixation on optical bench by insert technology (see PM2)
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HYPER: ESA Feasibility StudyHYPER Symposium 1Fundamental Physics and Applications in SpaceCNES, Paris, 5.11.2002 Conclusions and outlook
Present status and work to be done
Already done:•Previous work analysed and reference mission for study defined•Hyper performance requirements breakdown completed•Orbit trade-off completed•Disturbance environment analysed•Payload configuration trade-off completed and baseline defined•DFAC simulator developed and almost completed (detailed verification pending)•Optical bench and Precision Star Tracker conceptual design and budgets completed•Optical bench finite elements model (thermal, structural) almost completed•2. AOCS elements (Inertial sensor and FEEP´s) assessment completed
Still to be done:•DFAC (2.AOCS) simulation campaign•Payload module thermo-elastic distortion analysis and design re-finement•Precision Star Tracker detailed design•Spacecraft configuration and subsystems update•Ground testing assessment•Hyper road map (technology developments, payload)
Payload detailed design and technology development first priority
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