analysis of the in-flight injection of the...
TRANSCRIPT
ANALYSIS OF THE IN-FLIGHT INJECTION OF THE LISA PATHFINDER TEST-MASS
INTO A GEODESIC
Daniele Bortoluzzi (1,2) on behalf of the LISA Pathfinder Collaboration(*), Davide Vignotto (1), Andrea Zambotti (1),
Ingo Köker(3), Hans Rozemeijer(4), Jose Mendes(4), Paolo Sarra(5), Andrea Moroni(5), Paolo Lorenzi(5)
(1) University of Trento, Department of Industrial Engineering, via Sommarive, 9 - 38123 Trento, Email:
[email protected], [email protected], [email protected]
(2) Trento Institute for Fundamental Physics and Application / INFN, Italy.
(3) AIRBUS DS GmbH, Willy-Messerschmitt-Strasse 1 Ottobrunn, 85521, Germany, Email:
(4) European Space Operations Centre, European Space Agency, 64293 Darmstadt, Germany, Email:
[email protected], [email protected]
(5) OHB Italia S.p.A., via Gallarate, 150 – 20151 Milano, Italy, Email: [email protected], [email protected],
(*) Full list and affiliations attached in the end of the document
ABSTRACT
LISA Pathfinder is a mission that demonstrates some key
technologies for the measurement of gravitational waves.
The mission goal is to set two test masses (TMs) into
purely geodesic trajectories. The grabbing positioning
and release mechanism (GPRM) grabs and releases each
TM from any position inside its housing. The injection
phase is critical, because the free-floating TM can be
electrostatically controlled only if its linear and angular
velocities are less than 5μm/s and 100 μrad/s
respectively. Since the first injections showed significant
deviations from the expectation, a dedicated release test
campaign was performed at the end of the extended
mission phase, in order to explore different injection
strategies. The analysis of the releases shows that a
mechanism configuration out of the nominal one is
compatible with the in-flight test results. The paper
presents the findings of the in-orbit operation of the
GPRM and a possible interpretation of the underlying
dynamics.
1. INTRODUCTION
Many space missions, especially the ones dealing with
gravitational phenomena, use a free-floating mass as a
reference for their measurements ([1]). Missions based
on this principle where launched since the seventies
(TRIAD satellite, [2]). The main advantage of having a
free floating body as a reference is the fact that the
instrument resolution is improved if compared to
experiments where a mechanical contact is present
between the proof mass and the satellite ([3]).
During the launch phase and the early orbit phase, the
sensing mass is accelerated at the point that, if it is let free
to move, it can damage the inner part of the housing
surrounding it. In some missions locking the sensing
mass is not mandatory, since the mass itself is small, as
well as the gaps with respect to its housing. On the
contrary, other missions require a lock mechanism that
secures the sensing body and prevents impacts with the
surroundings housing.
The sensing body, from the locked condition, has then to
be released into free-fall to start the in-flight operations;
as a consequence, the release into free-fall of the proof
mass is a critical aspect for these missions, since it is a
necessary step to start the science phase. Different
technologies are nowadays available to perform a release
into freefall, for example electric motors, shape memory
actuators, solenoids, paraffin actuators, thermal cutters,
piezoelectric etc. In designing the release mechanism,
which is in contact with the proof mass before releasing
it, unavoidable forces arising at the contacting surfaces
must be taken into account.
Among many space missions, LISA Pathfinder (LPF , [4]
and [5]) represents a very interesting and challenging
case of study, since the requirements imposed to the
release operations are very tiny in terms of the residual
momentum of the test mass (TM).
Figure 1 The LISA Pathfinder scientific payload. The
free-floating test masses are visible, hosted inside their
housings.
_____________________________________________________________________________________________ Proc. 18. European Space Mechanisms and Tribology Symposium 2019, Munich, Germany, 18.-20. September 2019
LPF mission, launched in 2015 and ended in 2017, was
the precursor of a gravitational-waves space observer,
called LISA (launched scheduled for 2034). The goal of
LPF was to demonstrate some key technologies to be
implemented in LISA, showing that a LISA-like proof
mass can be injected into a pure geodesic trajectory to a
level of force noise below 10 fN in the measurement
bandwidth 1–30 mHz ([6]).
The LISA Pathfinder scientific payload include many
mechanisms. The one on which this work focuses in is
the grabbing positioning and release mechanism
(GPRM). As its name suggests, it is responsible of
locking (grabbing) the TM from any position inside its
housing, repositioning it in the center, and then release in
into freefall ([7]).
2. SYSTEM DESCRIPTION AND NOMINAL
RELEASE PROCEDURE
Inside the LISA-pathfinder spacecraft, there are two
gravitational reference sensors (GRS 1 and 2), both
containing a TM (referenced as TM1 and TM2). Each
TM is a cubed shaped 1.96 kg gold-coated Au/Pt mass
(see Fig. 1), and is inserted in an electrode housing (EH),
with gaps between TM and surrounding walls of 3-4 mm.
The housing is covered with electrodes, that both
generate the electrostatic control force, to stabilize the
TM after the release, and provide the measurement of TM
position and attitude for the control loop.
Figure 2 Reference system of one GRS. The TM position
inside the GRS is described by three translations (x, y, z)
and three rotations (θ, η, φ).
A reference system, centred in the EH, is used to describe
TM positions and attitudes (see Fig. 2). It is defined with
three translations {x, y, z} and three rotations {θ, η, φ},
since the TM has six degrees of freedom (DOFs). Inside
each GRS there is a GRPM, that is composed by two
cylindrical pistons, called plungers, that are nominally
aligned to the z-axis. The plungers are moved
independently along z-axis by means of a piezo-walk
actuator (called NEXLINE). The half of the GPRM on
the z+ side is called top, the one on the z- side is called
bottom. Two force sensors (one for each half of the
mechanism) measure the preload applied on the TM by
each plunger.
Plungers ends are designed to fit into two squared
indentations present on the z faces of the TM to lock it
during the grabbing phase.
The plunger on the z+ side has a conical end, the plunger
on the z- side has a pyramidal end. This design is adopted
in order to not over-constrain the TM rotation around the
z axis (defined by angle φ).
Inside each plunger, there is a coaxial gold tip, with a
diameter of 0.8 mm. The tip protrudes from the plunger
end when a voltage is applied to a piezo stack actuator
attached to it. A pre-loaded spring pushes back the tip if
the voltage is reduced (Fig. 3).
As previously said, the GPRM is the mechanism that
operates the release into freefall of the proof mass. The
nominal release procedure consists of grabbing the TM
with the plungers. Then repositioning the grabbed TM in
the centre of the EH. After that, the handover manoeuvre
is performed: it consists of extruding the tips from the
plunger ends, and retracting at the same time the two
plungers, in order to maintain the desired preload force
on the TM. The nominal maximum extraction of the tips
is 18 μm, and before reaching the TM surface, they travel
4 μm (free-stroke), so the z distance between TM and
plunger at release is very tiny, nominally 14 μm.
Figure 3 Sketch of the plunger, with extended tip
touching the TM.
After the handover the TM is said to be in the pre-release
phase, held only by the two tips, that are in contact with
the TM on two specific zone called landing areas. To
release the TM, tips are simultaneously and quickly
retracted (thanks to the pre-loaded spring); this
guarantees the minimization of any asymmetric contact
force on the TM and to break the adhesion force. In the
ideal case, this procedure should produce a zero TM
momentum after release.
The requirement on the TM residual velocity (i.e. the
free-falling velocity after the release) are set to 5 μm/s
and 100 μrad/s for translations and rotations respectively.
_____________________________________________________________________________________________ Proc. 18. European Space Mechanisms and Tribology Symposium 2019, Munich, Germany, 18.-20. September 2019
These velocity limits are required in order for the
electrostatic control force to be able to stabilize the TM
in the centre on the EH.
Given the geometry of the GPRM, the forces acting on
the TM at the release should be directed only along the z-
axis, with very low components along x and y due to not
perfect alignment of plungers and tips. In the case of a
nominal release (or quasi-nominal, i.e. with tiny
misalignment between TM and plunger), the residual
momentum on the TM is given by two main
contributions:
- the asymmetry of the adhesion-pull force
between the two contacts.
- the asymmetry of retraction, that can convert
symmetric adhesion into momentum.
These two contributions have been deeply analysed. A
dedicated experimental setup, called transferred
momentum measurement facility (TMMF), was designed
to study the adhesion contribution in detail ([8] and [9]).
The effect of the second contribution have been
simulated taking into account possible delays in the tips
retraction ([10]).
It has been shown that the GPRM, in the nominal
working condition, is capable of releasing the TM
respecting the requirement on the residual momentum
with a success rate greater than 95% ([11],[12]).
Once the two GPRM (of TM1 and TM2) have been
assembled, their functionality have been successfully
tested on-ground in the in-flight configuration ([13]).
Unfortunately, during on-ground tests is not possible to
replicate a release, due to the influence of the Earth
gravitational field.
3. IN-FLIGHT RELEASES
The first releases were performed in-flight in February
2016, with the nominal release procedure. Release results
did not confirm the expectations, as reported in Tab. 1.
Two main problems were detected, for both GRS1 and
GRS2:
- the TMs residual velocities were higher than the
requirement, so the actuation was not able to
control and stabilize the TM avoiding impacts.
- the z component of the translational velocity was
not the main one, and high rotational velocities
where recorded.
The TM stabilization was possible only after few
minutes; the strategy was to wait for impacts to damp the
TM momentum until the controller was able to capture it.
Since this behaviour of the GPRMs was totally
unexpected, and since similar mechanisms should be
used in LISA, the mission was extended and a GPRM test
campaign was scheduled in the end of mission phase.
In the extended mission experimental campaign, several
tests were performed. Many release strategies were
tested, and an upgraded release procedure was
implemented. Last tests were performed with an
automatized improved release procedure ([14]).
Table 1 Release velocities of TM1 and TM2, from two
releases performed in February 2016. Velocities are
much higher than the requirements.
Unit μm/s μrad /s
DOF 𝑣x 𝑣y 𝑣z 𝜔𝜃 𝜔η 𝜔φ
TM1 -2.9 -
20.3
-
56.7 681.3
-
797.4 1084.6
TM2 11.6 -
27.2
-
16.2 1035.4 -30.0 -429.7
Req. 5 5 5 100 100 100
The manoeuvres that were tested during the extended
mission phase and that improved the GRPM performance
are:
- Hammering: moving plungers back and forth
using the NEXLINE, with extended tips, to
improve the plunger ends settling into the TM
indentations before the release. Hammering is
performed just after the handover.
- Slow release tip retraction: repositioning the tips
instead of quickly retracting them, from max
extension (nominal 18 μm) to 12 μm.
- Slow plunger retraction: command a low
velocity plunger retraction, few seconds after
release.
A scheme of the phases of the improved release
procedure is depicted in Fig. 4. By applying the described
strategies, the percentages of compliant releases
increased (i.e. releases respecting the requirement on the
TM residual velocity).
Our focus will be mainly on the release velocities after
the tip release (referred as tip release velocity, that is the
actual release instant, at which the TM starts to free fall).
In general, at tips retraction the TM velocities sometimes
are compliant with the requirement, and sometimes they
are not.
Figure 4 Phases of the improved release procedure. The
release instant represents the fast or slow tip retraction
instant.
Few instants after the tip release, when plungers start
being retracted, the TM momentum is often increased.
This unexpected phenomenon suggests that there is an
_____________________________________________________________________________________________ Proc. 18. European Space Mechanisms and Tribology Symposium 2019, Munich, Germany, 18.-20. September 2019
undesired interaction between TM and plunger. It must
be clarified that, for the control force actuation, the
velocities of interest are the one after the plungers
retraction, but this is not the aim of the study presented
in this work.
If the GRPM had worked under nominal condition at
release, without any plunger-TM interaction, the residual
velocities obtained in-flight would not be explainable.
For this reason, we made the hypothesis of non-nominal
working conditions of the GPRM. The hypothesis is
reinforced looking at the high residual velocities,
recorded on all six degrees of freedom, and observing the
TM momentum change at plunger retraction.
To confirm this hypothesis, in-flight releases data have
been analysed. Unfortunately, for many tests, it is not
easy to estimate the release velocity of the TM (at tips
retraction), since many impacts took place right after the
release instant. Another limiting factor is the relatively
low sampling time, 10 Hz, not sufficient to precisely
detect instants at which there is an impact. In this work,
due the limitations yet described, only a subset of all the
test is considered.
The tests having at least three aligned sampling points
(along all the six DOFs of the TM) after the release where
selected, since in free falling condition the velocity is
constant. The algorithm used to select these tests checked
a “linearity assumption”, based on the distribution of the
noise affecting the readings. These tests are defined as
aligned tests.
4. IMPULSES ANALYSIS
The analysis of the velocity of the TM after the tip release
allows to extract a subset of aligned tests among all the
test of the extended mission campaign. For each aligned
test, the release velocities along the 6 DOFs of the TM
can be considered as free fall velocities and are estimated
through a linear fit. Given the free fall velocities a
dynamical model can be applied in order to estimate the
impulses applied to the TM at the release. From now on,
we will consider only aligned tests in the analysis.
The set of the aligned tests is mainly composed of tests
with low TM velocities at the tips retraction. In
particular, the slow tip releases show translational
velocities respecting the requirements and, in general,
also compliant rotational velocities (except for few cases
with one rotational velocity slightly greater than the
limit).
Aligned tests comprehend also non-compliant tests (i.e.
tests with at least one velocity higher than the
requirement). They are composed mainly of fast tip
release tests (the nominal tip release strategy), which
show high translational and rotational velocities (also 10
times the requirement). As shown in Fig. 5, for these non-
compliant fast-tip tests the translational velocities lie
mainly in the x-z plane, with an inclination close to 45°
(i.e. x and z components of the velocity are comparable).
This fact suggests that the nominal release described in
section 2, assumed in the on-ground experiments, cannot
explain the measured velocity of the TM. It can be proved
that, based on the geometry of the system (maximum
relative inclination between tip and TM and dimension of
the contact surface of the TM), unfeasible values of
adhesive pulls or blocking forces would be required in
order to obtain the measured motion as the sum of two
opposite inclined forces between tips and TM. This is
mainly due to the high x component of the velocity (since
in a nominal release the TM should move only along the
z axis).
Figure 5 Translational velocities of the TM at release.
Non-compliant fast-tip tests from the subset of the
aligned tests are shown. Main momentum components lie
on the x-z plane.
Therefore, we can reasonably assume that a contact
between plunger and TM occurred at the tip release. This
hypothesis is supported by the inclination of the
translational velocities, which is similar to the inclination
of the grabbing indentation. This suggests that an impulse
orthogonal to the indentation surfaces near the plunger-
TM contact area was applied to the TM.
Based on this finding, we assume that, for the non-
compliant fast tip tests, the measured momentum of the
TM at the tip release is given by impulses applied to the
TM at the indentation contact zone, as depicted in Fig.
6Figure 8. For each plane (x-z and y-z) and each z face
of the TM, we assume two impulses orthogonal to the
indentation surface (whose inclination w.r.t. the z axis is
α). In general, the two impulses are not equilibrated,
therefore we can split their sum in the sum of two
balanced impulses (u and w in Fig. 6) and an unbalanced
impulse (t). The effect of the two balanced impulses will
_____________________________________________________________________________________________ Proc. 18. European Space Mechanisms and Tribology Symposium 2019, Munich, Germany, 18.-20. September 2019
be only a resultant along the z axis, while the unbalanced
impulse gives a contribution to z motion, transversal
motion, and rotation. It’s important to notice that each of
the impulses shown in Fig. 6 can be (in principle) the
resultant of many repeated impulses; moreover, we
assume the impulses are applied in the middle of the
grabbing contact surface.
Figure 6 Impulses given from the plunger to the TM in
the hypothesis there is a contact between them at release.
The TM indentation geometry is simplified.
Since in the considered tests the TM is not moving before
the release and starts moving linearly approximately 0.1-
0.2 seconds after the tip release, we assume that the linear
motion of the TM is created by the application of an
unknown number of impulses immediately after the tip
release.
In Fig. 7, we draw the unbalanced impulses for each
plane, x-z and y-z, at each side of the TM. Impulses x and
y components are on the top (z+) side are defined as 𝜄1x
and 𝜄1y. While on the bottom side they are defined as 𝜄2
x
and 𝜄2y.
Each of them is associated to the corresponding z impulse
through the constant tan(α), where α is the inclination of
the indentation surface w.r.t. the z axis. Balance impulses
are not represented since they do not affect rotation.
Figure 7 Unbalanced impulses scheme, in both planes x-
z (on the left) and y-z (on the right). Distances a and b
are estimated from CAD model.
From the scheme of Fig. 7, we can write the relations
between the impulses applied to the TM and the
measured momentum:
𝜄1𝑥 + 𝜄2
𝑥 = 𝑀𝑣𝑥 (1)
ι1y
+ ι2𝑦
= 𝑀𝑣𝑦 (2)
(𝜄2
𝑦− 𝜄1
𝑦)𝑎 − (𝜄2𝑦
− 𝜄1𝑦
) tan(𝛼) 𝑏 = 𝐼𝑥𝑥 𝜔𝜃 (3)
(ι1
x − ι2x)𝑎 − (ι1
x − ι2x) 𝑡𝑎𝑛(α) 𝑏 = 𝐼yy ωη (4)
−(|𝜄1x| + |𝜄1
y|) 𝑡𝑎𝑛(𝛼) + (|𝜄2
x| + |𝜄2y
|) 𝑡𝑎𝑛(𝛼) + 𝜄𝑟𝑒𝑠z = 𝑀𝑣𝑧 (5)
where a and b are the arms of the rotations (estimated
from the system geometry) and 𝜄resz is the residual
impulse along z, i.e. the quote of z momentum that cannot
be attributed to the unbalanced impulses. Equations 1-4
can be solved independently, leading to a unique solution
for the unbalanced impulses; once the unbalanced
impulses are computed, the residual impulse can be
calculated from Eq. 5. It’s important to remark that the
nature of the residual impulse cannot be determined: it
can be the sum (or the difference) of many effects that do
not affect the TM rotation, like the balanced impulses of
Fig. 6 or any force applied from the tip to the TM (which
we assume directed mainly along the z axis).
In Fig. 8, as an example, the impulses for one of the
considered tests from TM1 are plotted. One can see that,
according to the solution of the system of equations 1-5,
the main unbalanced impulse is applied by the pyramidal
(bottom) plunger; the z component of the pyramidal
impulse constitutes a high percentage of the total z
momentum. The results are similar for all the non-
compliant fast tip tests of TM1.
Figure 8 Typical impulses on the TM in the fast tip
release tests. The residual impulse along z is small,
compared to the total z impulse.
The computation has been applied to all the non-
compliant fast tip tests; in Fig. 9 we compare the z
momentum with residual impulses (with associated
_____________________________________________________________________________________________ Proc. 18. European Space Mechanisms and Tribology Symposium 2019, Munich, Germany, 18.-20. September 2019
uncertainty). It can be seen that (like for the case depicted
in Figure 8. 8) for all the tests the residual impulse is
significantly lower than the z momentum, thus
suggesting that the orthogonal impulses, computed in
order to justify the transversal (x, y) and rotational (θ, η)
motions of the TM, can also motivate a high percentage
of the z momentum.
Figure 9 Total impulses along z for the considered tests.
Only a fraction of the total momentum (blue) is due to the
residual momentum along z (orange), that respects the
requirement of 10 kg μm/s in many cases. The red bars
are the expected values. The small rectangles on top of
each columns represent the 1-σ uncertainty around the
expected value.
As previously commented, the residual impulse cannot
be attributed to a unique effect since its nature is
undetermined; it could be due multiple effects on one
side of the TM (like adhesion, or balanced push of the
plunger), as well as to opposite (subtractive) effects on
the two sides. In general the residual impulse (considered
with its uncertainty) is compliant with the requirement
for z momentum (10 kg μm/s); for some tests it is higher
than the requirement, but still generating a momentum
that the capacitive actuation can control, as happened in-
flight ([14]). This means that critical z momentum is
essentially due to the (non-nominal) plunger-TM contact
at the indentations.
Summarizing, the transversal and rotational velocities of
the TM can be motivated only through a TM-plunger
contact at the indentations; the resulting impulses are
necessarily associated to a z impulse which is detrimental
for the final TM momentum, independently of other
effects (like adhesion) whose contribution cannot be
determined.
5. BI-STABILE BEHAVIOUR OF THE
MECHANISM
After analysing the effect of the lateral push of the
plungers on the z component of the impulses, the
attention was focused on one of the possible causes of
this phenomenon.
An interesting behaviour of the mechanism was
discovered from an in-flight test on the repositioning
capability of the GPRM. The test consisted in
repositioning the TM while it was grabbed by the
plungers with a preload of 2 N. The TM was repositioned
along the z axis actuating the NEXLINE, moving both
plunger simultaneously to maintain the force as constant
as possible.
In this experiment the z position of the TM is
commanded, while the other five DOFs depend on the
kinematic of the system. In the nominal case, the
correlation between the five dependent DOFs and the z
position of the TM should be zero. In other words, the
TM rotations and x, y translations should not depend on
its z position.
In the in-flight experiments, the real systems showed a
correlation of the five DOFs with z postion. In particular,
the orientation of the TM around η is clearly correlated
with the direction of motion of the plungers.
In Fig. 10, the TMs z position is plotted as function of
time, along with the attitude around η. When the direction
of motion is reversed, the TMs suddenly rotate of
approximately 60 μrad. So, there is a kind of bi-stable
equlibrium of the plungers, that orient themselves
accordingly to their direction of motion.
Figure 10 Correlation between η rotation and z position
of the TMs during in-flight repositioning test.
This behaviour is taking place on the x-z plane (since η
is the rotation around y axis), that is the same plane where
the main components of the impulses lie. This fact
suggests a correlation between the bi-stable configuration
of the system and the high x, z components of the release
velocity.
6. CONCLUSIONS
The mechanism responsible for the release of the proof
masses in the LISA Pathfinder Space mission presents
some criticalities.
It was designed to perform a dynamic release into
freefall, that fulfilled a very strict requirement in terms of
residual velocities of the test masses (5 μm/s and 100
μm/s for translations and rotations respectively).
Nominal release is performed with a quick and
simultaneous retraction of two tips, in contact with the
TM on a small area on two opposite faces.
An extensive set of on-ground tests demonstrate that the
forces present at release (adhesion and pull force due to
_____________________________________________________________________________________________ Proc. 18. European Space Mechanisms and Tribology Symposium 2019, Munich, Germany, 18.-20. September 2019
retraction delay) are small enough that the requirement
should be fulfilled more than 95% of the cases.
In-flight releases showed unexpected velocities, that lead
to undesired impact on the TM, and prevent its
controllability and stabilisation.
A dedicated in-flight campaign of tests was carried out,
to explore the performance of the GPRM under different
working conditions. The release procedure was updated,
adding some phases to the standard manoeuvre.
Analysing in-flight data, focusing on the impulses
received from the TM, it has been proved that the GPRM
has not worked in nominal conditions.
The TM received impulses at release from unexpected
impacts with the plungers. The impulse along the z
direction has been subdivided into two contributions:
- The contribution dependent on the net lateral
push of the plunger, that produces also a z
impulse due to the inclination of the contact
zone.
- The residual impulse generated by adhesion,
delay asymmetry and probably other effects
(that cannot be predicted).
The first contribution is the main one and produced the
higher z velocity on the TM. The second contribution is
lower, and always produced controllable z velocity on the
TM.
A possible explanation of the lateral push of the plungers
on the TM comes from the analysis of other in-flight data,
that showed some kind of bi-stable equilibrium of the
plungers on the x-z plane (the one where most release
impulses lie).
To summarise, high TM residual velocities are due to the
fact that the forces that arise at release are not the ones
tested on-ground.
Further developments of this work will concentrate on
establishing what are all the possible causes that can lead
to unexpected contacts between TM and plungers.
Since the GPRM mechanism will be used in the future
coming mission LISA, the presented findings can be used
to improve its design and enhancing its performance.
7. REFERENCES
1. Bortoluzzi, D & Foulon, Bernard & García
Marirrodriga, César & Lamarre, D. Object injection
in geodesic conditions: In-flight and on-ground
testing issues. Advances in Space Research (2010).
1358-1379.10.1016/ j.asr.2010.01.023.
2. Staff of the Space Department, Staff of the Guidance
and Control Laboratory A Satellite Freed of all but
Gravitational Forces: “TRIAD I”, J. Spacecraft 11,
pp. 637–644, 1974.
3. Touboul, P., Foulon, B., Willemenot, E.
Electrostatic space accelerometers for present and
future missions, Acta Astronaut, 45, 605–617, 1999.
4. ESA, LISA Pathfinder. First steps to observing
gravitational waves from space. ESA Brochure, BR-
323 (2015): 1-16.
5. F. Antonucci, M. Armano, H. Audley, G. Auger, M.
Benedetti, P. Binetruy, J. Bogenstahl, D. Bortoluzzi,
P. Bosetti, N. Brandt, M. Caleno, P. Caizares, A.
Cavalleri, M. Cesa, M. Chmeissani, A. Conchillo,
G. Congedo, I. Cristofolini, M. Cruise, K.
Danzmann, F. D. Marchi, M. Diaz-Aguilo, I.
Diepholz, G. Dixon, R. Dolesi, N. Dunbar, J. Fauste,
L. Ferraioli, V. Ferrone, W. Fichter, E. Fitzsimons,
M. Freschi, A. G. Marin, C. G. Marirrodriga, R.
Gerndt, L.Gesa, F. Gilbert, D. Giardini,C.Grimani,
A. Grynagier, B. Guillaume, F. Guzmn, I. Harrison,
G. Heinzel, V. Hernndez, M. Hewitson, D.
Hollington, J. Hough, D. Hoyland, M. Hueller, J.
Huesler, O. Jennrich, P. Jetzer, B. Johlander, N.
Karnesis, C. Killow, others, X. Llamas, I. Lloro, A.
Lobo, R. Maarschalkerweerd, S. Madden, D.
Mance, I. Mateos, P. W. McNamara, J. Mendes, E.
Mitchell, A. Monsky, D. Nicolini, D. Nicolodi, M.
Nofrarias, F. Pedersen, M. Perreur-Lloyd, E.
Plagnol, P. Prat, G. D. Racca, J. Ramos-Castro, J.
Reiche, J. A. R. Perez, D. Robertson, H. Rozemeijer,
J. Sanjuan,A. Schleicher,M. Schulte, D. Shaul, L.
Stagnaro, S. Strandmoe, F. Steier, T. J. Sumner, A.
Taylor, D. Texier, C. Trenkel, H.-B. Tu, S. Vitale,
G. Wanner, H. Ward, S. Waschke, P. Wass, W. J.
Weber, T. Ziegler, and P. Zweifel, “The LISA
pathfinder mission,” Classical Quantum Gravity,
vol. 29, no. 12, pp. 124014-1–124014-11, 2012.
6. Armano, Michele & Audley, H & Baird, J &
Binetruy, P & Born, Míriam & Bortoluzzi, D &
Castelli, E & Cavalleri, A & Cesarini, Andrea &
Cruise, A. M. & Danzmann, Karsten & de Deus
Silva, M & Diepholz, I & Dixon, G & Dolesi, R &
Ferraioli, Luigi & Ferroni, Valerio & Fitzsimons,
Enda & Freschi, M & Zweifel, Peter. (2018).
Beyond the Required LISA Free-Fall Performance:
New LISA Pathfinder Results down to 20 μhz.
Physical Review Letters. 120.
10.1103/PhysRevLett.120.061101.
7. P. M¨ausli, R. Romano, K. Lips, and P. Nellen,
“GPRM - Design description,” ESA, Frascati, Italy,
ESA Internal Document S2-HTS-DDD-3001, 2007.
8. Benedetti, M & Bortoluzzi, D & De Cecco, M.
(2007). A Momentum Transfer Measurement
Experiment Between Contacting Bodies in the
Presence of Adhesion Under Near-Zero Gravity
Conditions. 10.1007/978-1-4020-6239-1_215.
9. C. Zanoni and D. Bortoluzzi. Experimental-
Analytical Qualification of a Piezoelectric
Mechanism for a Critical Space Application.
_____________________________________________________________________________________________ Proc. 18. European Space Mechanisms and Tribology Symposium 2019, Munich, Germany, 18.-20. September 2019
IEEE/ASME Transactions on Mechatronics 20.1
(2015): 427-437.
10. D. Bortoluzzi, J. W. Conklin, and C. Zanoni.
Prediction of the LISA Pathfinder release
mechanism in-flight performance. Advances in
Space Research 51.7 (2013): 1145-1156.
11. D. Bortoluzzi et al. Injection of a Body into a
Geodesic: Lessons Learnt from the LISA Pathfinder
Case, Aerospace Mechanism Symposium 2016,
NASA/CP-2016-219090.
12. C. Zanoni and D. Bortoluzzi. Experimental-
Analytical Qualification of a Piezoelectric
Mechanism for a Critical Space Application.
IEEE/ASME, Transactions on Mechatronics 20.1
(2015): 427-437.
13. I. Köker et al. Alignment and Testing of the GPRM
as Part of the LTP Caging Mechanism. 15th
European Space Mechanisms and Tribology
Symposium. Vol. 718. 2013.
14. Jose Mendes. TM Release Experiments. ESA
internal document, 2017.
*LISA Pathfinder Collaboration - Dated: June 11, 2019
M Armano,1 H Audley,2 J Baird,3 P Binetruy,3, * M Born,2 D
Bortoluzzi,4 E Castelli,5 A Cavalleri,6 A Cesarini,7
A M Cruise,8 K Danzmann,2 M de Deus Silva,9 I Diepholz,2
G Dixon,8 R Dolesi,5 L Ferraioli,10 V Ferroni,5
E D Fitzsimons,11 M Freschi,9 L Gesa,12 F Gibert,5
D Giardini,10 R Giusteri,5, † C Grimani,7 J Grzymisch,1
I Harrison,13 G Heinzel,2 M Hewitson,2 D Hollington,14
D Hoyland,8 M Hueller,5 H Inchauspé,3, 15 O Jennrich,1 P
Jetzer,16 N Karnesis,3 B Kaune,2 N Korsakova,17 C J Killow,17
J A Lobo,12, * I Lloro,12 L Liu,5 J P López-Zaragoza,12
R Maarschalkerweerd,13 D Mance,10 N Meshksar,10
V Martìn,12 L Martin-Polo,9 J Martino,3 F Martin-Porqueras,9
I Mateos,12 P W McNamara,1 J Mendes,13 L Mendes,9
M Nofrarias,12 S Paczkowski,2 M Perreur-Lloyd,17
A Petiteau,3 P Pivato,5 E Plagnol,3 J Ramos-Castro,18
J Reiche,2 DI Robertson,17 F Rivas,12 G Russano,5, ‡
J Slutsky,19 C F Sopuerta,12 T Sumner,14 D Texier,9
J I Thorpe,19 D Vetrugno,5 S Vitale,5 G Wanner,2 H Ward,17
P J Wass,14, 15 W J Weber,5 L Wissel,2 A Wittchen,2 and
P Zweifel10
1. European Space Technology Centre, European
Space Agency, Keplerlaan 1, 2200 AG Noordwijk,
The Netherlands
2. Albert-Einstein-Institut, Max-Planck-Institut fur
Gravitationsphysik und Leibniz Universität
Hannover, Callinstraße 38, 30167 Hannover,
Germany
3. APC, Univ Paris Diderot, CNRS/IN2P3, CEA/lrfu,
Obs de Paris, Sorbonne Paris Cit´e, France
4. Department of Industrial Engineering, University of
Trento, via Sommarive 9, 38123 Trento, and Trento
Institute for Fundamental Physics and Application /
INFN
5. Dipartimento di Fisica, Universitàdi Trento and
Trento Institute for Fundamental Physics and
Application / INFN, 38123 Povo, Trento, Italy
6. Istituto di Fotonica e Nanotecnologie, CNR-
Fondazione Bruno Kessler, I-38123 Povo, Trento,
Italy
7. DISPEA, Universitàdi Urbino “Carlo Bo”, Via S.
Chiara, 27 61029 Urbino/INFN, Italy
8. The School of Physics and Astronomy, University of
Birmingham, Birmingham, UK
9. European Space Astronomy Centre, European
Space Agency, Villanueva de la Ca˜nada, 28692
Madrid, Spain
10. Institut fur Geophysik, ETH Zurich, Sonneggstrasse
5, CH-8092, Zurich, Switzerland
11. The UK Astronomy Technology Centre, Royal
Observatory, Edinburgh, Blackford Hill, Edinburgh,
EH9 3HJ, UK
12. Institut de Ciències de l1Espai (CSIC-IEEC),
Campus UAB, Carrer de Can Magrans s/n, 08193
Cerdanyola del Vallès, Spain
13. European Space Operations Centre, European
Space Agency, 64293 Darmstadt, Germany
14. High Energy Physics Group, Physics Department,
Imperial College London, Blackett Laboratory,
Prince Consort Road, London, SW7 2BW, UK
15. Department of Mechanical and Aerospace
Engineering, MAE-A, P.O. Box 116250, University
of Florida, Gainesville, Florida 32611, USA
16. Physik Institut, Universität Zurich,
Winterthurerstrasse 190, CH-8057 Zurich,
Switzerland
17. SUPA, Institute for Gravitational Research, School
of Physics and Astronomy, University of Glasgow,
Glasgow, G12 8QQ, UK
18. Department d1Enginyeria Electrônica, Universitat
Politècnica de Catalunya, 08034 Barcelona, Spain
19. Gravitational Astrophysics Lab, NASA Goddard
Space Flight Center, 8800 Greenbelt Road,
Greenbelt, MD 20771 USA
*Deceased. †Current address: [email protected] ‡[email protected]
_____________________________________________________________________________________________ Proc. 18. European Space Mechanisms and Tribology Symposium 2019, Munich, Germany, 18.-20. September 2019