LISA Pathfinder measuring pico-meters and femto-newtons in space

Transcription

1 LISA Pathfinder measuring pico-meters and femto-newtons in space M Hewitson for the LPF team Barcelona, February 15th 2012

2 Observing from Space 2

3 Observing from Space 2

4 Observing from Space Push down to much lower frequencies: mhz 2

5 Observing from Space Push down to much lower frequencies: mhz Stability of ground-based instruments is difficult to achieve at these frequencies seismic wall ~10 Hz 2

6 Observing from Space Push down to much lower frequencies: mhz Stability of ground-based instruments is difficult to achieve at these frequencies seismic wall ~10 Hz 2

7 Observing from Space Push down to much lower frequencies: mhz Stability of ground-based instruments is difficult to achieve at these frequencies seismic wall ~10 Hz Going to space: Increase arm-length (increase sensitivity, L/L ) 2

8 Observing from Space Push down to much lower frequencies: mhz Stability of ground-based instruments is difficult to achieve at these frequencies seismic wall ~10 Hz Going to space: Increase arm-length (increase sensitivity, L/L ) Quite environment (reduce noise) 2

9 LISA concept 3

10 LISA concept Thruster Telescope Thruster Thruster OB PM GRS Thruster SC PM Telescope OB GRS Thruster Thruster 3

11 LISA concept Thruster Telescope Thruster Thruster OB PM GRS SC PM GRAVITATIONAL REFERENCE SENSOR (GRS) Test Mass + Drag free Thruster Telescope OB GRS Thruster Thruster 3

12 LISA concept Thruster Telescope Thruster Thruster OB PM GRS SC PM GRAVITATIONAL REFERENCE SENSOR (GRS) Test Mass + Drag free Thruster GRS OB Telescope OPTICAL METROLOGY Optical Bench (OB) + Phasemeter (PM) Thruster Thruster 3

13 LISA concept Thruster Telescope Thruster Thruster OB PM GRS SC PM GRAVITATIONAL REFERENCE SENSOR (GRS) Test Mass + Drag free Thruster GRS OB Telescope OPTICAL METROLOGY Optical Bench (OB) + Phasemeter (PM) Thruster THRUSTER Thruster 3

14 LISA Measurement -> LISA Pathfinder 4

15 LISA Measurement -> LISA Pathfinder a long way 4

16 LISA Measurement -> LISA Pathfinder a long way 4

17 The LISA Pathfinder Mission Technology demonstrator for a LISA-like mission: Local interferometry micro-newton propulsion Gravitational Reference Sensor Drag-free control LPF will be placed in orbit around L1 Requirements relaxed 1 order of magnitude in differential acceleration LPF req. 3x10-14 m/s 1mHz 1 order of magnitude higher frequency LPF meas. bandwidth 1mHz < f < 30mHz 5

18 The LISA Pathfinder Mission Technology demonstrator for a LISA-like mission: Local interferometry micro-newton propulsion Gravitational Reference Sensor Drag-free control LPF will be placed in orbit around L1 Requirements relaxed 1 order of magnitude in differential acceleration LPF req. 3x10-14 m/s 1mHz 1 order of magnitude higher frequency LPF meas. bandwidth 1mHz < f < 30mHz 5

19 The LISA Pathfinder Team United Kingdom: - Optical Bench - Phase-meter - Charge Management France: - Laser modulator Spain: - Data Diagnostics System - Data Management Unit Netherlands: - ISS SCOE Germany: - Co-Principle Investigator - LTP Architect (Astrium) - Laser Switzerland: - ISS Front End Electronics Italy: - Principle Investigator - Inertial Sensor - Caging Mechanism 6

20 Payloads on board LISA Pathfinder The LISA Technology Package (LTP) European payload Full system thrusters, test-masses, inertial sensor, interferometers, etc The Disturbance Reduction System (DRS) NASA payload Alternative thrusters Alternative drag-free control 7

21 Payloads on board LISA Pathfinder The LISA Technology Package (LTP) European payload Full system thrusters, test-masses, inertial sensor, interferometers, etc The Disturbance Reduction System (DRS) NASA payload Alternative thrusters Alternative drag-free control 7

22 The LISA Technology Package (LTP) 8

23 x-axis measurement 9

24 IFO X1: SC-TM1 measurement 10

25 Drag-free on TM1 11

26 IFO X12: TM1-TM2 displacement 12

27 Suspension control 13

28 Spacecraft 14

29 Spacecraft 14

30 Spacecraft 14

31 . 15

32 The LTP 16

33 The LTP Data Management Unit Reference Laser Unit Optical Bench Phasemeter Inertial Sensor Vacuum Enclosure 16

34 17

35 Current status (what s missing?) 18

36 Current status (what s missing?) Micro-propulsion system problems with Ca FEEPs in the past may now be solved ESA have been looking at alternative systems modified Ca FEEPs, Indium FEEPS, Cold gas, mini-rit, Colloid further testing to be done before deciding on a solution 18

37 Current status (what s missing?) Micro-propulsion system problems with Ca FEEPs in the past may now be solved ESA have been looking at alternative systems modified Ca FEEPs, Indium FEEPS, Cold gas, mini-rit, Colloid further testing to be done before deciding on a solution Caging mechanism Construction of original launch-lock proved challenging ESA investigating alternatives New cam-based system, single-shot mechanism single-shot mechanism has been selected 18

38 Testing: On-station Thermal Tests Uses a thermal-optical qualification model in place of the flight LTP Consists of a flight optical bench, with flight mounting struts, and thermal mass dummies of the inertial sensors 19

39 Testing: On-station Thermal Tests Uses a thermal-optical qualification model in place of the flight LTP Consists of a flight optical bench, with flight mounting struts, and thermal mass dummies of the inertial sensors Alberto Lobo s talk 19

40 Science Goals 20

41 Science Goals Obtain the best geodesic motion possible quietest differential acceleration of the two TMs 3 x m s -2 / Hz at 1 mhz pm accuracy position measurement of TM-SC, TM-TM commissioning by changing system parameters determine best configuration by experiments 20

42 Science Goals Obtain the best geodesic motion possible quietest differential acceleration of the two TMs 3 x m s -2 / Hz at 1 mhz pm accuracy position measurement of TM-SC, TM-TM commissioning by changing system parameters determine best configuration by experiments Develop a noise model of the system allows the projection of the performance of technologies to LISA 20

43 Science Goals Obtain the best geodesic motion possible quietest differential acceleration of the two TMs 3 x m s -2 / Hz at 1 mhz pm accuracy position measurement of TM-SC, TM-TM commissioning by changing system parameters determine best configuration by experiments Develop a noise model of the system allows the projection of the performance of technologies to LISA 20

44 Mission Operations We have 90 days to achieve the goals characterise and optimise the system All days are filled with pre-planned experiments some flexibility is built-in Data analysis of the experiments will be done in real-time 21

45 Mission Operations We have 90 days to achieve the goals characterise and optimise the system All days are filled with pre-planned experiments some flexibility is built-in Data analysis of the experiments will be done in real-time 21

46 Experiments Technical studies are broken down into investigations These investigations are then packed into the time-line Measurement of Parasitic Voltages Measurement of differential acceleration noise on LISA Pathfinder Measurement of cross-talk between the y-axis and the x-axis on the LTP Measurement of LTP dynamical coefficients by system identification Analysis of Data from the Radiation Monitor on LISA Pathfinder Thermal experiments on board the LTP Magnetic experiments on board the LTP OPD noise investigations for LTP Laser frequency noise characterisation for LTP Laser Amplitude Noise Characterisation for LTP The Drift Mode for LISA Pathfinder 22

47 Estimating residual differential TM acceleration (1) The direct observables of the instrument are displacements We need to estimate residual forces acting on the TMs We can: estimate acceleration of the SC derived from SC-TM1 displacement estimate differential acceleration of two TMs derived from differential displacement of two TMs 23

48 Estimating residual differential TM acceleration (2) DS 1 C o = A + DS 1 o n 24

49 Estimating residual differential TM acceleration (2) DS 1 C o = A + DS 1 o n observation noise 24

50 Estimating residual differential TM acceleration (2) DS 1 C o = A + DS 1 o n residual acceleration observation noise 24

51 Estimating residual differential TM acceleration (2) measurement DS 1 C o = A + DS 1 o n residual acceleration observation noise 24

52 Estimating residual differential TM acceleration (2) system DS 1 measurement C o = A + DS 1 o n residual acceleration observation noise 24

53 Estimating residual differential TM acceleration (2) DS 1 C o = A + DS 1 o n o n A D 1 S C o 24

54 Estimating residual differential TM acceleration (2) DS 1 C o = A + DS 1 o n o n A D 1 S C o 24

55 Estimating residual differential TM acceleration (2) DS 1 C o = A + DS 1 o n o n A D 1 S C o 24

56 Parameter estimation Employ different estimation methods to work with multiple inputs, multiple outputs All methods require a parametric model of the system 25

57 Parameter estimation 8 3 x 10 Time origin: :36: UTC 9 4 Linear Nonlinear MCMC Data 2 1 x 10 Time origin: :36: UTC Linear Nonlinear MCMC 3 2 Amplitude [m] Amplitude [m] Time [s] x Time [s] x 10 26

58 Parameter estimation 3 10 Linear Nonlinear MCMC Data 2 1 Amplitude [m] 7 Time origin: :36: UTC x 10 3 Spectral density [m Hz 1/2] Amplitude [m] 8 x 10 2 Time origin: :36: UTC Linear Linear Nonlinear Nonlinear MCMC MCMC Noise o_ Time [s] x Time [s] Frequency [Hz] x

59 Results using mission simulator We can simulate experiments using the mission simulator 3D, non-linear, time-domain simulation We can recover the parameters with high precision very dependent on having a good model 27

60 Data Analysis M Hewitson, LPF, Sheffield, 13th September

61 Data Analysis DA Software Toolbox of algorithms to act on the data Repository for storing data products Client for submitting and retrieving to/from repository Documentation and testing M Hewitson, LPF, Sheffield, 13th September

62 Data Analysis DA Software Toolbox of algorithms to act on the data Repository for storing data products Client for submitting and retrieving to/from repository Documentation and testing DA Activities Simulate experiments Design, build and test analyses and associated tools Train scientists M Hewitson, LPF, Sheffield, 13th September

63 Data Analysis DA Software LTPDA Toolbox of algorithms to act on the data Repository for storing data products Client for submitting and retrieving to/from repository Documentation and testing DA Activities Simulate experiments Design, build and test analyses and associated tools Train scientists M Hewitson, LPF, Sheffield, 13th September

64 Noise budget Various noise contributions can be directly measured Some noise couplings must be modelled using estimates of physical parameters together with a system model Some noise contributions must be estimated/ modelled from design 29

65 Requirements Differential Force Noise Budget 30

66 Free-flight experiment 31

67 Free-flight experiment Capacitive actuation will be close to limiting around 1mHz 31

68 Free-flight experiment Capacitive actuation will be close to limiting around 1mHz Do an experiment with the actuation off must be short otherwise the TM will drift too far repeat many times 31

69 Free-flight experiment Capacitive actuation will be close to limiting around 1mHz Do an experiment with the actuation off must be short otherwise the TM will drift too far repeat many times Experiment: kick test-mass away turn off actuation let the test-mass drift (in parabola) repeat 31

70 Simulation 32

71 PSD Estimate Simulation with requirement-level noises but x3 reduced direct TM force noise 33

72 Towards s/lisa/%s 34

73 Conclusion LPF is well on its way! Most of the hardware is there awaiting thrusters and launch lock Most of the experiments are already defined many are even tested with DA in place We have a clear path to launch Launch in

74 Thank you 36