LISA Pathfinder

1
LISA Pathfinder

• Paul McNamara for the LPF Team
• LISA Pathfinder Project Scientist
• ESA/ESTEC
• Email Paul.McNamara_at_esa.int

2
Summary

• Introduction
• History of LPF
• Mission Overview
• Technologies
• Launch and Orbit
• Current Status
• Conclusions

3
Introduction

• LISA Pathfinder is a technology demonstration
  mission for LISA
• The mission will test in flight
• Inertial sensors
• Precision interferometry between free floating
  test masses
• Drag Free and Attitude Control System (DFACS)
• Micro-Newton propulsion technology
• Field Emission Electric Propulsion (FEEP)
• Colloidal thrusters
• The basic idea of LISA Pathfinder is to squeeze
  one arm of the LISA constellation from 5 million
  km to a few tens of cm!

4
History of LPF - ELITE

• First proposed as ELITE (European LIsa
  TEchnology) in 1998
• Differential acceleration goal of
• 10-14ms-2/vHz over 1 100mHz
• Single payload
• Two inertial sensors, homodyne
• Michelson interferometer readout
• Geostationary orbit
• Target launch date of 2002

5
History of LPF SMART 2

• ELITE proposal was refined and proposed to ESA in
  2000 as SMART-2 (Small Missions for Advanced
  Research in Technology)
• Two free-flying satellites with laser
• and microwave link
• Goal to demonstrate drag-free for
• LISA and formation flying for Darwin
• Three payloads
• LISA Technology Package
• US LISA Technology Package
• Darwin Technology Package
• Approved by SPC in November 2000
• Launch window in 2006

6
LISA Pathfinder

• After initial study, SMART-2 was descoped and
  renamed LISA Pathfinder
• Darwin Pathfinder cancelled
• Single spacecraft with two payloads
• European provided LTP
• NASA provided DRS
• Both payloads comprised
• Two inertial sensors
• Laser metrology
• Micro-Newton Thrusters
• DFACS
• Orbit Lissajous orbit around L1

LPF Spacecraft
GRS
LTP
7
LISA Pathfinder Current Status

• Due to budget and schedule
• constraints, DRS was descoped
• GRS and metrology cancelled
• DRS will now use the LTP sensors
• Launch vehicle Rockot
• Launch Date 4th Qtr 2009
• LPF now in Phase C/D
• Detailed Design Phase

LPF
LTP
8
Mission Goal 1

• The primary goal of LISA Pathfinder is to verify
  that a test mass can be put in pure gravitational
  free-fall with residual acceleration noise less
  than
• over a frequency range
• of 1-30mHz

9
Mission Goal 2

• A secondary goal, which has now become directly
  relevant to LISA, is to demonstrate laser
  metrology using free floating mirrors with a
  displacement sensitivity of
• over a frequency range of 1-30mHz

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Experimental Philosophy
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LPF Technology

• Interferometry
• Laser
• Optical Bench
• Phase Meter
• Inertial Sensor
• Proof mass
• Electrode housing
• Front end electronics
• Caging mechanism
• UV discharge system
• Vacuum System
• Micro-Newton Thrusters

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LISA Technology Package
Inertial Sensors
Optical Bench
Coil
Magnetometers
13
LISA Technology Package

• Procurement and manufacture of the LTP funded by
  European member states and ESA

France Laser modulator Germany PI, LTP
Architect (Astrium), Laser Italy PI, Inertial
Sensor (ISS), Caging Mechanism Netherlands ISS
SCOE Spain Data Diagnostics System, Data
Management Unit Switzerland ISS Front End
Electronics United Kingdom Optical Bench,
Phase-meter, Charge Management
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LTP Team

• LTP workshop, Trento 2005

15
Reference Laser Unit

• Manufactured by TESAT GmbH (Germany)
• Non-planar ring oscillator (NPRO) design
• 25 mW single mode optical output power
• Polarization maintaining single mode fiber
  output
• 10 W electrical power
• LTP Reference Laser Unit
• is identical to the LISA master
• oscillator

16
Optical Bench Interferometer

• Manufactured by University Of Glasgow (Scotland)
• Zerodur baseplate with silicate bonded fused
  silica components
• Flight hardware is currently being procured
• OBI scheduled to be delivered to Astrium GmbH in
  February 2007

• Optical bench manufacturing technique directly
  applicable to LISA optical bench manufacture
• Lessons learned will be used to optimise the
  design of the LISA optical bench

17
Optical Bench
Fibre injectors
Reference
x1
Int 1
Int 2
Frequency
x1-x2
18
OB EM performance
19
Optical Bench Interferometer

• Construction of the LTP Optical Bench
  Interferometer,
• Christian Killow, Wednesday, 1550

Photograph of OBI EM under test
Photograph of OBI EM
20
Phase-meter

• Manufactured by University of Birmingham (UK)
• Original design from AEI Hannover
• Based on Single Bit Discrete Fourier Transform
  (SBDFT) architecture
• Could be used as phase meter
• for LISA proof mass
• interferometer

21
Phase-meter performance
22
Proof Mass

• Procured from Heraeus, Germany
• 46mm cube of Gold-Platinum
• 73 Au27 Pt
• Mass 1.96kg
• Indentation on top and chamfered
• corners for caging mechanism
• Similar to LISA test mass
• Magnetic Susceptibility requirement
• relaxed by one order of magnitude
• A sensitive Torsion Balance for LISA
• Proof Mass Testing,
• Stephen Schlamminger, Tuesday, 1650

Raw Material
Polished
Polished and Coated
23
Electrode Housing

• Manufactured by Laben (Italy)
• Molybdenum and conducting ceramics
• Gold coated sapphire electrodes
• LISA electrode housing will be identical to the
  LPF housing

24
Front-End Electronics

• Manufactured by Contraves (Switzerland)
• In conjunction with ETH Zurich
• Fully redundant electronics
• Two sensing/actuation units
• One switching unit
• Cables to ISS not redundant
• Further development required
• for LISA
• 24-bit space qualified ADC
• Space qualified bi-polar auto-zero
• amplifier

25
Caging Mechanism

• Caging Mechanism by Laben (Italy)
• Clamp the test-mass in position and sustain
  launch load
• Pre-load 3000N
• Break large adhesion created by vibration under
  load
• No lubricants possible
• All gold coated surfaces
• Release the test-mass around the center of the
  electrode housing with low enough kinetic energy
  such that proof mass can be electrostatically
  captured
• Release velocity lt10mm/s!
• LPF Caging Mechanism requirements identical to
  that of LISA
• LPF Hardware can be directly transferred to LISA

26
Caging Mechanism

• Caging mechanism now consists of three actuators
• Hydraulic launch lock
• Piezo-driven positioning mechanism
• Piezo-driven release mechanism
• Breadboard of positioning and release mechanisms
  currently undergoing vibe testing
• Adhesion testing currently underway
• Caging Mechanism CDR scheduled for October 06

27
Caging Mechanism
High Load Hydraulic Actuator (3000N)
Positioning Actuator (100N)
Release Actuator (10N)
28
Charge Management

• Manufactured by Imperial College London (UK)
• Based on UV photo-electric discharge
• Non-contact
• Can be used to discharge either
• proof mass or electrode housing
• Redundant
• Same system as will be used in LISA
• Only difference may be in the choice of
• UV light source
• LED rather than Mercury

29
Charge Management

• Two discharge modes available
• Continuous
• Minimise stiffness
• No coherent components
• Periodic
• Less noise from charging
• Lose measurement time
• Both will be tested on LPF
• Ground testing has already been performed using
  torsion pendulum at University of Trento
• Charge Management for LISA Pathfinder and
  Development for LISA, Markus Schulte, Tuesday,
  1730

30
Inertial Sensor Ground Testing

• Inertial sensor cannot be fully tested on ground
• Hence the need for LISA Pathfinder
• Ground testing focussed on torsion pendulums
• Dedicated torsion pendulums constructed at the
  University of Trento
• Noise in torsion pendulum approaching that of
  LISA Pathfinder!!
• Only in one axis
• Light-weighted proof mass
• Cannot fully represent cross-coupling

31
Inertial Sensor Ground Testing
University of Trento single mass torsion pendulum
?10-13ms-2/vHz
32
Ground Testing Presentations

• Free-fall and LISA sensitivity below 0.1mHz,
• William Weber, Tuesday, 1550
• Torsion pendulum investigation of thermal
  gradient-induced forces on LISA test masses,
• Mauro Hueller, Tuesday, 1630
• A sensitive torsion balance for LISA Proof mass
  modelling,
• Stephen Schlamminger. Tuesday 1650
• Outgassing, temperature gradients, and the
  radiometer effect in LISA A torsion pendulum
  investigation,
• Scott Pollack, Tuesday, 1710

33
Micro-Newton Thrusters

• Micro-Newton thrusters for LTP based on Field
  Emission Electric Propulsion (FEEP)
• DRS will use Colloid micro-Newton
• thrusters
• Two developments underway in Europe
• ALTA Caesium Slit FEEP (Italy)
• ARCS Indium Needle FEEP (Austria)
• After first phase of development,
• down-select will be made between
• the two thruster architectures
• This design will be taken to flight
• hardware

34
Micro-Newton Thrusters

• FEEPS are being designed as the LISA thruster
• FEEP development not only for LPF
• Same FEEP will be used on Microscope
• Colloid needs additional development (primarily
  lifetime) to meet the LISA requirements

35
Micro-Newton Thruster

• LISA Pathfinder FEEP Subsystem
• Davide Nicolini, Thursday 1730

Slit FEEP
Needle FEEP

• Colloid micro-Newton thruster development for
  ST7-DRS and LISA missions
• John Ziemer, Thursday 1750

Colloid
36
LTP Integration
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LTP Core Assembly
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DRS

• DRS originally comprised two inertial sensors, an
  interferometric readout, DFACS and micro-Newton
  Thrusters
• Due to budget and schedule over-runs, the mission
  was descoped to only include DFACS (running on
  dedicated computer) and micro-Newton thrusters
• DRS will now use the LTP inertial sensors
• Both flight hardware units are currently
  undergoing lifetime and environmental testing
• Flight hardware to be delivered to ESA in 1st Qtr
  2007

45
DRS

• Colloid micro-Newton thruster development for
  ST7-DRS and LISA missions, John Ziemer,
  Thursday 1750

IAU on shaker table
Colloid micro-Newton thruster
46
Launch Vehicle

• Baseline launch vehicle Rockot
• Procured from Eurockot, Bremen
• Breeze KM upper stage
• Proven vehicle with heritage
• SS19 ICBM!
• Launch from Plesetsk, Russia (latitude 63o)
• Injection into 200x900 km orbit
• Max lift-off weight of S/C 1910 kg
• Facility to be upgraded for bi-propellant
• fuelling (vapour traps, waste disposal, etc)

47
Launch Vehicle

• Target launch vehicle is VEGA
• ESA directive to target European launchers
• Procured from Arianespace
• New launcher
• LPF could be first flight!
• Launch from Kourou, French Guiana (latitude 5o)
• No free injection into L1 Lissajous orbit
• Requires injection burn

48
Launch Sites
Plesetsk Winter temperature -30oC!
Kourou Winter temperature 28oC!
49
Orbit

• LPF launched into high inclination orbit of
  200x900km
• 15 apogee raising manoeuvers required to deliver
  LPF to L1
• High inclination orbit allows free transfer (no
  orbit insertion required)

• Prop module separate during transfer phase
• Final orbit is Lissajous orbit around L1

50
Mission Timeline
T L 0
L 16d
L 50d
L 66d
L 94d
L 184d
L 214d
Fundamental Physics?
LTP Ops
DRS Ops
Despin Orbit Corr
IOOP SCIENCE OPERATIONS
Transfer Phase
Commiss- ioning
LEOP
Launch
Separation
51
LISA Pathfinder Status

• Multi-Lateral Agreement (MLA) defining LTP flight
  hardware responsibility signed in May 2005
• LTP flight hardware being delivered by ESA member
  states
• LPF Industrial Prime Contractor chosen in 2002
• Astrium UK, Stevenage
• LTP Architect
• Astrium GmbH, Friedrichshafen
• All industrial contracts for spacecraft flight
  hardware have been placed
• e.g. Structures, star-trackers, solar array, etc

52
LPF Status

• LPF passed Mission Preliminary Design Review
  (M-PDR) in February 2006
• M-PDR consolidates the LTP PDR, System PDR,
  Ground Segment Requirements Review, and DRS CDR
• LISA Pathfinder is now in PHASE C/D Detailed
  Design Phase

53
LPF Main Reviews/Schedule

• System Requirements Review Jun-Nov 2004
• Technology Readiness Review 22 June 2005
• Preliminary Design Review 29 September 2005
• LTP Preliminary Design Review 31 August 2005
• Ground Segment Req Review 24 November 2005
• DRS Delta-CDR/Risk Review 20 January 2006
• Mission Preliminary Design Review 16 February
  2006
• LTP Subsys. Critical Design Review Q3-Q4 2006
• LTP Critical Design Review Q1-Q2 2007
• Critical Design Review Q3 2007
• Flight Acceptance Review Q4 2009
• Launch Q4 2009

54
Conclusions

• LPF and LTP have now entered Phase C/D Detailed
  Design Phase
• LTP flight hardware delivery is scheduled to
  begin in Q1 2007
• Significant knowledge has already been gained
  from the LPF project
• This knowledge will be used in the development of
  the LISA design
• Additional lessons learned will be transferred to
  LISA
• IT, ground segment, commissioning
• Launch scheduled for 4th Quarter 2009
• Results to be presented at the 8th International
  LISA Symposium!!

55
Thank you

• ESA ESTEC
• ESA ESAC
• ESA ESOC
• EADS Astrium UK
• EADS Astrium GmbH
• University of Trento
• Albert Einstein Institute
• University of Glasgow
• University of Birmingham
• Imperial College London
• ETH Zurich
• Institut d-Estudis Espacials de Catalunya
• Universidad Politecnica de Barcelona
• APC Paris

• Laben
• Carlo Gavazzi Space
• ALTA
• ARCS
• Contraves
• Kaiser Threde
• NTE
• SCISYS
• Spacebel
• SRON
• Technologica
• TESAT
• ZARM
• JPL
• NASA Goddard
• BUSEK