Disentangling the
magnetic force noise contribution
in
LISA Pathfinder
M. Nofrarias
Institut de Ciències de l’Espai (IEEC-CSIC)
Motivation
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
2
Magnetic Diagnostics in LPF
•
Magnetic diagnostics in LPF:
-
4 Fluxgate magnetometers
2 Coils
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
3
Magnetic Diagnostics in LPF
•
Magnetic diagnostics in LPF:
-
4 Fluxgate magnetometers
2 Coils
X LISA Symposium - M Nofrarias
(1) Estimation test mass magnetic parameters
Gainesville - 20/05/14
- Injected signals
- Estimation force noise contribution
3
Magnetic Diagnostics in LPF
•
Magnetic diagnostics in LPF:
-
4 Fluxgate magnetometers
2 Coils
(1) Estimation test mass magnetic parameters
- Injected signals
- Estimation force noise contribution
(2) Magnetic field interpolation
- Characterisation of magnetic env.
- Contribution of mag. sources
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
3
Magnetic analysis #1: coils experiment
• Coils attached to ISH to apply a
force/torque on the TM
• The response must allow a
precise characterization of the
the moment and susceptibility
of the TMs
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
4
Magnetic analysis #1: coils experiment
• Coils attached to ISH to apply a
force/torque on the TM
• The response must allow a
precise characterization of the
the moment and susceptibility
of the TMs
Measured
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
4
Magnetic analysis #1: coils experiment
• Coils attached to ISH to apply a
force/torque on the TM
• The response must allow a
precise characterization of the
the moment and susceptibility
of the TMs
Measured
Unknown
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
4
Magnetic analysis #1: coils experiment
• Coils attached to ISH to apply a
force/torque on the TM
• The response must allow a
precise characterization of the
the moment and susceptibility
of the TMs
Measured
Unknown
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
4
STOC Simulation #4
• STOC Simulations are exercises to
train the team for LPF operations
-
different DA teams/sites
mission-like schedule
telecommand/telemetry as in
operations
• STOC end-to-end Simulation #4
(16-23 Nov 2013) included
magnetic characterisation
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
5
STOC Simulation #4
• STOC Simulations are exercises to
train the team for LPF operations
-
different DA teams/sites
mission-like schedule
telecommand/telemetry as in
operations
• STOC end-to-end Simulation #4
(16-23 Nov 2013) included
magnetic characterisation
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
5
STOC Simulation #4
• STOC Simulations are exercises to
train the team for LPF operations
-
different DA teams/sites
mission-like schedule
telecommand/telemetry as in
operations
Signal characteristics:
• STOC end-to-end Simulation #4
(16-23 Nov 2013) included
magnetic characterisation
X LISA Symposium - M Nofrarias
-
Gainesville - 20/05/14
Four frequencies: [1, 3, 5, 7 ] mHz
Fixed amplitude 1mA
Applying ~5uT (interplanetary ~10nT)
Duration 19h
5
Magnetic analysis pipeline
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
6
Magnetic analysis pipeline
Download
Preprocess
Acceleration
estimate
compute
mag. field
heterodyne
solve linear
system
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
6
Analysis pipeline - displacement
•
Analysis based on telemetry parameters
-
applied voltage on coils, TM displacement
magnetic experiment too close to CMS discharge (planning error)
LTPDA 2.8.dev (R2012a)
2014−05−18 21:53:44.894 UTC
ltpda: 637f026
iplot
LTPDA 2.8.dev (R2012a)
2014−05−19 17:51:48.281 UTC
ltpda: 637f026
−6
iplot
3
2
V1
V2
x 10
o1
o12
0
2
−2
Displacement [m]
Voltage [V]
1
0
−1
−4
−6
−8
−10
−12
−2
−14
−3
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Origin: 2013−11−18 08:00:01.000 − Time [s]
X LISA Symposium - M Nofrarias
5
5.5
−16
0.5
4
x 10
Gainesville - 20/05/14
1
1.5
2
2.5
3
3.5
4
4.5
Origin: 2013−11−18 08:00:01.000 − Time [s]
5
5.5
4
x 10
7
Analysis pipeline - displacement
•
Analysis based on telemetry parameters
-
applied voltage on coils, TM displacement
magnetic experiment too close to CMS discharge (planning error)
LTPDA 2.8.dev (R2012a)
2014−05−18 21:53:44.894 UTC
ltpda: 637f026
iplot
LTPDA 2.8.dev (R2012a)
2014−05−19 17:51:48.281 UTC
ltpda: 637f026
−6
iplot
3
2
V1
V2
x 10
o1
o12
0
2
−2
0
−1
−4
2
−8
−14
1.5
2
2.5
3
3.5
4
4.5
Origin: 2013−11−18 08:00:01.000 − Time [s]
5
5.5
0
−10
−2
1
o1
o12
1
−12
−3
0.5
x 10
−6
−16
0.5
4
x 10
−1
Displacement [m]
Displacement [m]
Voltage [V]
1
LTPDA 2.8.dev (R2012a)
2014−05−19 17:51:49.228 UTC
ltpda: 637f026
−8
iplot
−2
−3
−4
1
−5
1.5
2
2.5
3
3.5
4
4.5
Origin: 2013−11−18 08:00:01.000 − Time [s]
5
5.5
4
x 10
−6
−7
−8
0.5
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
1
1.5
2
2.5
3
3.5
4
4.5
Origin: 2013−11−18 08:00:01.000 − Time [s]
5
5.5
4
x 10
7
Analysis pipeline - force and torque
•
Translation into force and torques
-
requires system parameters (assumed to be known)
LTPDA 2.8.dev (R2012a)
2014−05−18 19:10:43.430 UTC
ltpda: 637f026
−9
iplot
1.29
LTPDA 2.8.dev (R2012a)
2014−05−18 19:58:13.898 UTC
ltpda: 637f026
−12
iplot
x 10
16
Force
x 10
−Torque
14
1.285
−2
TM Torque [kg m rad s ]
1.275
10
8
2
TM Force [kg m s−2]
12
1.28
1.27
1.265
6
4
2
1.26
1.255
3
0
−2
3.5
4
4.5
5
Origin: 2013−11−18 08:00:01.000 − Time [s]
X LISA Symposium - M Nofrarias
5.5
4
x 10
−4
3
Gainesville - 20/05/14
3.5
4
4.5
5
Origin: 2013−11−18 08:00:01.000 − Time [s]
5.5
4
x 10
8
Analysis pipeline - force and torque
•
Translation into force and torques
-
requires system parameters (assumed to be known)
LTPDA 2.8.dev
2.8.dev (R2012a)
(R2012a)
LTPDA
2014−05−18 19:10:44.524
19:10:43.430 UTC
UTC
2014−05−18
ltpda: 637f026
637f026
ltpda:
−9
−9
iplot
iplot
1.29
LTPDA 2.8.dev (R2012a)
2014−05−18 19:58:15.410
19:58:13.898 UTC
ltpda: 637f026
−12
iplot
x 10
16
Force
Force
lowpass(Force)
x 10
14
1.285
−Torque −Torque
lowpass( −Torque)
−2
TM Torque [kg m rad s ]
1.275
10
8
2
TM Force [kg m s−2]
12
1.28
1.27
1.265
6
4
2
1.26
1.255
3
0
−2
3.5
4
4.5
5
Origin: 2013−11−18 08:00:01.000 − Time [s]
X LISA Symposium - M Nofrarias
5.5
4
x 10
−4
3
Gainesville - 20/05/14
3.5
4
4.5
5
Origin: 2013−11−18 08:00:01.000 − Time [s]
5.5
4
x 10
8
Analysis pipeline - force and torque
•
Translation into force and torques. Spectra:
-
Force contribution at f0 and 2xf0
Torque contribution at f0
High frequency IFO noise
LTPDA 2.8.dev (R2012a)
2014−05−18 19:10:46.165 UTC
ltpda: 637f026
iplot
LTPDA 2.8.dev (R2012a)
2014−05−18 19:58:17.142 UTC
ltpda: 637f026
iplot
−10
−10
10
PSD(Force)
PSD( −Torque)
TM Torque [kg m2 rad s−2 Hz−1/2]
TM Force [kg m s−2 Hz−1/2]
10
−11
10
−12
10
−13
10
−14
10
−11
10
−12
10
−13
10
−14
−4
10
−3
10
−2
10
Frequency [Hz]
X LISA Symposium - M Nofrarias
−1
10
0
10
10
−4
10
Gainesville - 20/05/14
−3
10
−2
10
Frequency [Hz]
−1
10
0
10
9
Analysis pipeline - parameters
•
To determine the parameters:
-
heterodyne at the injected frequency to get
the coupling coefficients
solve the linear system
-
LTPDA 2.8.dev (R2012a)
2014−05−19 01:32:59.168 UTC
ltpda: 637f026
−11
iplot
1.5
x 10
LTPDA 2.8.dev (R2012a)
2014−05−19 01:32:59.168 UTC
ltpda: 637f026
−12
iplot
Force
Reconstructed
x 10
8
1
Force
Reconstructed
6
Force [kg m s−2]
Force [kg m s−2]
4
0.5
0
2
0
−2
−4
−0.5
−6
−8
3.76
−1
−1.5
3
3.5
4
4.5
5
Origin: 2013−11−18 08:00:01.000 − Time [s]
X LISA Symposium - M Nofrarias
3.78
3.8 3.82 3.84 3.86 3.88 3.9 3.92 3.94
Origin: 2013−11−18 08:00:01.000 − Time [s]
3.96
4
x 10
5.5
4
x 10
Gainesville - 20/05/14
10
Analysis pipeline - reconstructed force
LTPDA 2.8.dev (R2012a)
2014−05−16 09:54:53.382 UTC
ltpda: 637f026
iplot
−9
10
TM Force
−10
10
−11
−12
10
!
m kg
√
Hzs2
"
10
−13
10
−14
10
−15
10
−5
10
X LISA Symposium - M Nofrarias
−4
10
−3
10
−2
10
Fr equency [ Hz]
Gainesville - 20/05/14
−1
10
0
10
11
Analysis pipeline - reconstructed force
LTPDA 2.8.dev (R2012a)
2014−05−16 09:54:54.881
09:54:53.382 UTC
ltpda: 637f026
iplot
−9
10
TM Force
TM Force
component
0
−10
10
−11
−12
10
!
m kg
√
Hzs2
"
10
−13
10
−14
10
−15
10
−5
10
X LISA Symposium - M Nofrarias
−4
10
−3
10
−2
10
Fr equency [ Hz]
Gainesville - 20/05/14
−1
10
0
10
11
Analysis pipeline - reconstructed force
LTPDA2.8.dev
2.8.dev(R2012a)
(R2012a)
LTPDA
2014−05−1609:54:56.563
09:54:54.881
UTC
09:54:53.382UTC
2014−05−16
ltpda:637f026
637f026
ltpda:
iplot
iplot
−9
−9
10
10
TM Force
TMForce
Force
TM
component
component
0
0
−10
−10
2
10
10
0
component
−11
−11
m
m kg
kg
√
√
Hzs
Hzs22
""
10
10
−12
−12
!!
10
10
−13
10−13
10
−14
10−14
10
−15
10−15 −5
10
10−5
10
X LISA Symposium - M Nofrarias
−4
10−4
10
−3
−2
−2
10−3
10
10
10
Fr equency
equency [[ Hz]
Fr
Hz]
Gainesville - 20/05/14
−1
−1
10
10
0
0
10
10
11
Analysis pipeline - reconstructed force
LTPDA2.8.dev
2.8.dev(R2012a)
(R2012a)
LTPDA
2014−05−1609:54:56.563
09:54:54.881
UTC
09:54:53.382UTC
2014−05−16
ltpda:637f026
637f026
ltpda:
iplot
iplot
−9
−9
10
10
TM Force
TMForce
Force
TM
component
component
0
0
−10
−10
2
10
10
0
component
−11
−11
m
m kg
kg
√
√
Hzs
Hzs22
""
10
10
−12
−12
!!
10
10
−13
10−13
10
−14
10−14
10
−15
10−15 −5
10
10−5
10
−4
10−4
10
−3
−2
−2
10−3
10
10
10
Fr equency
equency [[ Hz]
Fr
Hz]
−1
−1
10
10
0
0
10
10
Last step in the pipeline is noise projection (requires magnetic field)
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
11
Magnetic analysis #2: magnetic field extrapolation
Magnetometers are fluxgate,
so magnetically active
-
Magnetic field needs to be
interpolated to TM position
Neural networks found to solve
the problem
-
need to be ‘trained’, so relying
on previous knowledge
1
σ1=9.2%
σ2=1.45%
0.5
0
−100
M Diaz-Aguilo, A Lobo, E Garcia-Berro.
Exp. Astronomy 30 2011
Pdf (Bz)
Gainesville - 20/05/14
σ1=7.91%
σ2=1.98%
TM1
TM2
σ1=4.42%
σ2=3.67%
TM1
TM2
0.5
0
100
Interpolation error (%)
0.5
0
−100
0
100
Interpolation error (%)
1
0
−100
X LISA Symposium - M Nofrarias
1
TM1
TM2
y
•
~ 30 magnetic active units
surrounding the TMs create a
complex mag. environment
Pdf (B )
-
0
100
Interpolation error (%)
1
Pdf (|B|)
•
can’t be near the TMs
Pdf (Bx)
•
σ1=4.28%
σ2=0.83%
TM1
TM2
0.5
0
−100
0
100
Interpolation error (%)
12
Exploring the LPF magnetic map
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
13
Exploring the LPF magnetic map
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
13
Exploring the LPF magnetic map
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
13
Exploring the LPF magnetic map
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
13
FEEP to Cold Gas thrusters
FEEPs
Cold Gas
(measured sources)
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
14
Sources contribution - magnetometers
Nominal contribution of sources to mag. measurement
40
20
0
0
10
20
Sources
Magnetometer #3
80
60
30
40
20
0
0
X LISA Symposium - M Nofrarias
10
Sources
20
30
ULU
CGLV MY
CGLV MXPY
CGLV PXPY
80
60
40
20
0
0
10
20
Sources
Magnetometer #4
80
30
CGLV MY
CGLV MXPY
CGLV PXPY
60
Magnetometer #2
60
PM d1
PM d2
CGLV MY
CGLV MXPY
CGLV PXPY
80
Mag. Field Contribution [%]
Magnetometer #1
Mag. Field Contribution [%]
Dominated by cold gas latch valves (CGLV)
CGLV MY
CGLV MXPY
CGLV PXPY
Mag. Field Contribution [%]
Mag. Field Contribution [%]
-
CCU
•
40
20
0
0
Gainesville - 20/05/14
10
Sources
20
30
15
Sources contribution - test masses
Test Mass #1
Test Mass #2
35
30
25
20
15
TM contribution
dominated by Cold
Gas LV (~70%)
•
Cold Gas Thrusters
(and other units) are
actively tested during
operations
•
Could we turn the
problem into a source
detection/subtraction ?
35
30
25
20
15
10
10
5
5
0
0
•
40
Mag. Field Contribution [%]
Mag. Field Contribution [%]
40
ULU
CGLV MY
CGLV MXPY
CGLV PXPY
45
CCU
CGLV MY
CGLV MXPY
CGLV PXPY
CCU
45
50
PM d1
PM d2
50
10
20
X LISA Symposium - M Nofrarias
30
0
0
10
Gainesville - 20/05/14
20
30
16
Magnetic sources location exercise
•
The LPF spacecraft went through a Thermal Balance/Thermal Vacuum test
(Oct 2011)
-
including magnetometers in the payload
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
17
OSTT campaign real data
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
18
OSTT campaign real data
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
18
OSTT campaign real data
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
18
OSTT campaign real data
X−component
0.03
0.02
0
−0.01
−0.02
−0.03
0.04
0.01
0
−0.01
−0.02
0.02
0
−0.02
−0.04
−0.03
−0.06
−0.05
−0.04
−0.08
4.325
4.33
4.335
4.34
4.345
Origin: 2011−10−22 08:54:09.938 − Time [s]
X LISA Symposium - M Nofrarias
4.35
5
x 10
−0.05
4.32
4.325
4.33
4.335
4.34
4.345
Origin: 2011−10−22 08:54:09.938 − Time [s]
Gainesville - 20/05/14
Mag. #1
Mag. #2
Mag. #3
Mag. #4
0.06
−0.04
−0.06
4.32
Z−component
0.08
Mag. #1
Mag. #2
Mag. #3
Mag. #4
0.03
Magnetic Field [uT]
0.01
LTPDA 2.8.dev (R2012a)
2014−05−17 13:50:41.515 UTC
ltpda: 637f026
iplot
Y−component
0.04
Mag. #1
Mag. #2
Mag. #3
Mag. #4
0.02
Magnetic Field [uT]
LTPDA 2.8.dev (R2012a)
2014−05−17 13:50:39.353 UTC
ltpda: 637f026
iplot
Magnetic Field [uT]
LTPDA 2.8.dev (R2012a)
2014−05−17 13:50:37.669 UTC
ltpda: 637f026
iplot
4.35
5
x 10
−0.1
4.32
4.325
4.33
4.335
4.34
4.345
Origin: 2011−10−22 08:54:09.938 − Time [s]
18
4.35
5
x 10
Magnetic MUSIC
•
LPF magnetometers can be treated as a sensor array
-
take advantage of geometry to locate sources
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
19
Magnetic MUSIC
•
LPF magnetometers can be treated as a sensor array
-
•
take advantage of geometry to locate sources
MUltiple SIgnal Classification (MUSIC)
method is based on subspace properties
of the covariance matrix to:
-
Schmidt, R.O, IEEE Vol. AP 34 (March 1986)
locate sources
determine number of sources in received
signal
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
19
Magnetic MUSIC
•
LPF magnetometers can be treated as a sensor array
-
•
take advantage of geometry to locate sources
MUltiple SIgnal Classification (MUSIC)
method is based on subspace properties
of the covariance matrix to:
-
Schmidt, R.O, IEEE Vol. AP 34 (March 1986)
locate sources
determine number of sources in received
signal
Music algorithm:
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
19
Magnetic MUSIC - real data
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
20
Magnetic MUSIC - real data
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
20
Magnetic MUSIC - real data
Star Tracker Electronics
Sun Sensor
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
20
Conclusions
•
Force noise due to magnetic coupling of the test mass
is the main contribution coming from direct forces at
low frequency
•
We have developed a data analysis pipeline for the inflight experiments with coils. Tested in STOC Simulation
•
Magnetic field needs to be interpolated to the TM
position. Work to improve better understand the structure
and main contributors of the magnetic field
•
We are developing tools to help locate magnetic sources
introducing a magnetic signal in the system
X LISA Symposium - M Nofrarias
Gainesville - 20/05/14
21
Thank you