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: [email protected] (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], [email protected] (*) Full list and affiliations attached in the end of the document
ABSTRACT surroundings housing. The sensing body, from the locked condition, has then to LISA Pathfinder is a mission that demonstrates some key be released into free-fall to start the in-flight operations; technologies for the measurement of gravitational waves. as a consequence, the release into free-fall of the proof The mission goal is to set two test masses (TMs) into mass is a critical aspect for these missions, since it is a purely geodesic trajectories. The grabbing positioning necessary step to start the science phase. Different and release mechanism (GPRM) grabs and releases each technologies are nowadays available to perform a release TM from any position inside its housing. The injection into freefall, for example electric motors, shape memory phase is critical, because the free-floating TM can be actuators, solenoids, paraffin actuators, thermal cutters, electrostatically controlled only if its linear and angular piezoelectric etc. In designing the release mechanism, velocities are less than 5μm/s and 100 μrad/s which is in contact with the proof mass before releasing respectively. Since the first injections showed significant it, unavoidable forces arising at the contacting surfaces deviations from the expectation, a dedicated release test must be taken into account. campaign was performed at the end of the extended Among many space missions, LISA Pathfinder (LPF , [4] mission phase, in order to explore different injection and [5]) represents a very interesting and challenging strategies. The analysis of the releases shows that a case of study, since the requirements imposed to the mechanism configuration out of the nominal one is release operations are very tiny in terms of the residual compatible with the in-flight test results. The paper momentum of the test mass (TM). 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 Figure 1 The LISA Pathfinder scientific payload. The contrary, other missions require a lock mechanism that free-floating test masses are visible, hosted inside their secures the sensing body and prevents impacts with the 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 each GRS there is a GRPM, that is composed by two the precursor of a gravitational-waves space observer, cylindrical pistons, called plungers, that are nominally called LISA (launched scheduled for 2034). The goal of aligned to the z-axis. The plungers are moved LPF was to demonstrate some key technologies to be independently along z-axis by means of a piezo-walk implemented in LISA, showing that a LISA-like proof actuator (called NEXLINE). The half of the GPRM on mass can be injected into a pure geodesic trajectory to a the z+ side is called top, the one on the z- side is called level of force noise below 10 fN in the measurement bottom. Two force sensors (one for each half of the bandwidth 1–30 mHz ([6]). mechanism) measure the preload applied on the TM by The LISA Pathfinder scientific payload include many each plunger. mechanisms. The one on which this work focuses in is Plungers ends are designed to fit into two squared the grabbing positioning and release mechanism indentations present on the z faces of the TM to lock it (GPRM). As its name suggests, it is responsible of during the grabbing phase. locking (grabbing) the TM from any position inside its The plunger on the z+ side has a conical end, the plunger housing, repositioning it in the center, and then release in on the z- side has a pyramidal end. This design is adopted into freefall ([7]). in order to not over-constrain the TM rotation around the z axis (defined by angle φ). 2. SYSTEM DESCRIPTION AND NOMINAL Inside each plunger, there is a coaxial gold tip, with a RELEASE PROCEDURE diameter of 0.8 mm. The tip protrudes from the plunger end when a voltage is applied to a piezo stack actuator Inside the LISA-pathfinder spacecraft, there are two attached to it. A pre-loaded spring pushes back the tip if gravitational reference sensors (GRS 1 and 2), both the voltage is reduced (Fig. 3). containing a TM (referenced as TM1 and TM2). Each As previously said, the GPRM is the mechanism that TM is a cubed shaped 1.96 kg gold-coated Au/Pt mass operates the release into freefall of the proof mass. The (see Fig. 1), and is inserted in an electrode housing (EH), nominal release procedure consists of grabbing the TM with gaps between TM and surrounding walls of 3-4 mm. with the plungers. Then repositioning the grabbed TM in The housing is covered with electrodes, that both the centre of the EH. After that, the handover manoeuvre generate the electrostatic control force, to stabilize the is performed: it consists of extruding the tips from the TM after the release, and provide the measurement of TM plunger ends, and retracting at the same time the two position and attitude for the control loop. 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 Figure 2 Reference system of one GRS. The TM position retracted (thanks to the pre-loaded spring); this inside the GRS is described by three translations (x, y, z) guarantees the minimization of any asymmetric contact and three rotations (θ, η, φ). force on the TM and to break the adhesion force. In the ideal case, this procedure should produce a zero TM A reference system, centred in the EH, is used to describe momentum after release. TM positions and attitudes (see Fig. 2). It is defined with The requirement on the TM residual velocity (i.e. the three translations {x, y, z} and three rotations {θ, η, φ}, free-falling velocity after the release) are set to 5 μm/s since the TM has six degrees of freedom (DOFs). Inside 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 Table 1 Release velocities of TM1 and TM2, from two in the centre on the EH. releases performed in February 2016. Velocities are Given the geometry of the GPRM, the forces acting on much higher than the requirements. the TM at the release should be directed only along the z- axis, with very low components along x and y due to not Unit μm/s μrad /s perfect alignment of plungers and tips. In the case of a nominal release (or quasi-nominal, i.e. with tiny DOF 푣x 푣y 푣z 휔휃 휔η 휔φ misalignment between TM and plunger), the residual - - - TM1 -2.9 681.3 1084.6 momentum on the TM is given by two main 20.3 56.7 797.4 contributions: - - TM2 11.6 1035.4 -30.0 -429.7 - the asymmetry of the adhesion-pull force 27.2 16.2 between the two contacts. Req. 5 5 5 100 100 100 - the asymmetry of retraction, that can convert
symmetric adhesion into momentum. The manoeuvres that were tested during the extended These two contributions have been deeply analysed. A mission phase and that improved the GRPM performance dedicated experimental setup, called transferred are: momentum measurement facility (TMMF), was designed - Hammering: moving plungers back and forth to study the adhesion contribution in detail ([8] and [9]). using the NEXLINE, with extended tips, to The effect of the second contribution have been improve the plunger ends settling into the TM simulated taking into account possible delays in the tips indentations before the release. Hammering is retraction ([10]). performed just after the handover. It has been shown that the GPRM, in the nominal working condition, is capable of releasing the TM - Slow release tip retraction: repositioning the tips respecting the requirement on the residual momentum instead of quickly retracting them, from max with a success rate greater than 95% ([11],[12]). extension (nominal 18 μm) to 12 μm. Once the two GPRM (of TM1 and TM2) have been - Slow plunger retraction: command a low assembled, their functionality have been successfully velocity plunger retraction, few seconds after tested on-ground in the in-flight configuration ([13]). release. Unfortunately, during on-ground tests is not possible to A scheme of the phases of the improved release replicate a release, due to the influence of the Earth procedure is depicted in Fig. 4. By applying the described gravitational field. strategies, the percentages of compliant releases increased (i.e. releases respecting the requirement on the 3. IN-FLIGHT RELEASES TM residual velocity). The first releases were performed in-flight in February Our focus will be mainly on the release velocities after 2016, with the nominal release procedure. Release results the tip release (referred as tip release velocity, that is the did not confirm the expectations, as reported in Tab. 1. actual release instant, at which the TM starts to free fall). Two main problems were detected, for both GRS1 and In general, at tips retraction the TM velocities sometimes GRS2: are compliant with the requirement, and sometimes they - the TMs residual velocities were higher than the are not. 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 Figure 4 Phases of the improved release procedure. The campaign was scheduled in the end of mission phase. release instant represents the fast or slow tip retraction In the extended mission experimental campaign, several instant. tests were performed. Many release strategies were tested, and an upgraded release procedure was Few instants after the tip release, when plungers start implemented. Last tests were performed with an being retracted, the TM momentum is often increased. automatized improved release procedure ([14]). This unexpected phenomenon suggests that there is an
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undesired interaction between TM and plunger. It must This fact suggests that the nominal release described in be clarified that, for the control force actuation, the section 2, assumed in the on-ground experiments, cannot velocities of interest are the one after the plungers explain the measured velocity of the TM. It can be proved retraction, but this is not the aim of the study presented that, based on the geometry of the system (maximum in this work. relative inclination between tip and TM and dimension of If the GRPM had worked under nominal condition at the contact surface of the TM), unfeasible values of release, without any plunger-TM interaction, the residual adhesive pulls or blocking forces would be required in velocities obtained in-flight would not be explainable. order to obtain the measured motion as the sum of two For this reason, we made the hypothesis of non-nominal opposite inclined forces between tips and TM. This is working conditions of the GPRM. The hypothesis is mainly due to the high x component of the velocity (since reinforced looking at the high residual velocities, in a nominal release the TM should move only along the recorded on all six degrees of freedom, and observing the z axis). 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 Figure 5 Translational velocities of the TM at release. can be considered as free fall velocities and are estimated Non-compliant fast-tip tests from the subset of the through a linear fit. Given the free fall velocities a aligned tests are shown. Main momentum components lie dynamical model can be applied in order to estimate the on the x-z plane. impulses applied to the TM at the release. From now on, we will consider only aligned tests in the analysis. Therefore, we can reasonably assume that a contact The set of the aligned tests is mainly composed of tests between plunger and TM occurred at the tip release. This with low TM velocities at the tips retraction. In hypothesis is supported by the inclination of the particular, the slow tip releases show translational translational velocities, which is similar to the inclination velocities respecting the requirements and, in general, of the grabbing indentation. This suggests that an impulse also compliant rotational velocities (except for few cases orthogonal to the indentation surfaces near the plunger- with one rotational velocity slightly greater than the TM contact area was applied to the TM. limit). Based on this finding, we assume that, for the non- Aligned tests comprehend also non-compliant tests (i.e. compliant fast tip tests, the measured momentum of the tests with at least one velocity higher than the TM at the tip release is given by impulses applied to the requirement). They are composed mainly of fast tip TM at the indentation contact zone, as depicted in Fig. release tests (the nominal tip release strategy), which 6Figure 8. For each plane (x-z and y-z) and each z face show high translational and rotational velocities (also 10 of the TM, we assume two impulses orthogonal to the times the requirement). As shown in Fig. 5, for these non- indentation surface (whose inclination w.r.t. the z axis is compliant fast-tip tests the translational velocities lie α). In general, the two impulses are not equilibrated, mainly in the x-z plane, with an inclination close to 45° therefore we can split their sum in the sum of two (i.e. x and z components of the velocity are comparable). 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 From the scheme of Fig. 7, we can write the relations impulse gives a contribution to z motion, transversal between the impulses applied to the TM and the motion, and rotation. It’s important to notice that each of measured momentum: the impulses shown in Fig. 6 can be (in principle) the 푥 푥 resultant of many repeated impulses; moreover, we 휄1 + 휄2 = 푀푣푥 (1) assume the impulses are applied in the middle of the y 푦 grabbing contact surface. ι1 + ι2 = 푀푣푦 (2)
푦 푦 푦 푦 (휄2 − 휄1 )푎 − (휄2 − 휄1 ) tan(훼) 푏 = 퐼푥푥 휔휃 (3)
x x x x (ι1 − ι2)푎 − (ι1 − ι2) 푡푎푛(α) 푏 = 퐼yy ωη (4)
x y x y z −(|휄1| + |휄1|) 푡푎푛(훼) + (|휄2| + |휄2|) 푡푎푛(훼) + 휄푟푒푠 = 푀푣푧 (5)
where a and b are the arms of the rotations (estimated z from the system geometry) and 휄res 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
Figure 6 Impulses given from the plunger to the TM in not affect the TM rotation, like the balanced impulses of the hypothesis there is a contact between them at release. Fig. 6 or any force applied from the tip to the TM (which The TM indentation geometry is simplified. we assume directed mainly along the z axis). In Fig. 8, as an example, the impulses for one of the Since in the considered tests the TM is not moving before considered tests from TM1 are plotted. One can see that, the release and starts moving linearly approximately 0.1- according to the solution of the system of equations 1-5, 0.2 seconds after the tip release, we assume that the linear the main unbalanced impulse is applied by the pyramidal motion of the TM is created by the application of an (bottom) plunger; the z component of the pyramidal unknown number of impulses immediately after the tip impulse constitutes a high percentage of the total z release. momentum. The results are similar for all the non- In Fig. 7, we draw the unbalanced impulses for each compliant fast tip tests of TM1. plane, x-z and y-z, at each side of the TM. Impulses x and x y components are on the top (z+) side are defined as 휄1 y x and 휄1 . While on the bottom side they are defined as 휄2 y and 휄2 . 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 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. Figure 7 Unbalanced impulses scheme, in both planes x- z (on the left) and y-z (on the right). Distances a and b The computation has been applied to all the non- are estimated from CAD model. 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 along the z axis actuating the NEXLINE, moving both in Figure 8. 8) for all the tests the residual impulse is plunger simultaneously to maintain the force as constant significantly lower than the z momentum, thus as possible. suggesting that the orthogonal impulses, computed in In this experiment the z position of the TM is order to justify the transversal (x, y) and rotational (θ, η) commanded, while the other five DOFs depend on the motions of the TM, can also motivate a high percentage kinematic of the system. In the nominal case, the of the z momentum. 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 Figure 9 Total impulses along z for the considered tests. equlibrium of the plungers, that orient themselves Only a fraction of the total momentum (blue) is due to the accordingly to their direction of motion. 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- Figure 10 Correlation between η rotation and z position flight ([14]). This means that critical z momentum is of the TMs during in-flight repositioning test. essentially due to the (non-nominal) plunger-TM contact at the indentations. This behaviour is taking place on the x-z plane (since η Summarizing, the transversal and rotational velocities of is the rotation around y axis), that is the same plane where the TM can be motivated only through a TM-plunger the main components of the impulses lie. This fact contact at the indentations; the resulting impulses are suggests a correlation between the bi-stable configuration necessarily associated to a z impulse which is detrimental of the system and the high x, z components of the release for the final TM momentum, independently of other velocity. effects (like adhesion) whose contribution cannot be determined. 6. CONCLUSIONS The mechanism responsible for the release of the proof 5. BI-STABILE BEHAVIOUR OF THE masses in the LISA Pathfinder Space mission presents MECHANISM some criticalities. After analysing the effect of the lateral push of the It was designed to perform a dynamic release into plungers on the z component of the impulses, the freefall, that fulfilled a very strict requirement in terms of attention was focused on one of the possible causes of residual velocities of the test masses (5 μm/s and 100 this phenomenon. μm/s for translations and rotations respectively). An interesting behaviour of the mechanism was Nominal release is performed with a quick and discovered from an in-flight test on the repositioning simultaneous retraction of two tips, in contact with the capability of the GPRM. The test consisted in TM on a small area on two opposite faces. repositioning the TM while it was grabbed by the An extensive set of on-ground tests demonstrate that the plungers with a preload of 2 N. The TM was repositioned 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 4. ESA, LISA Pathfinder. First steps to observing should be fulfilled more than 95% of the cases. gravitational waves from space. ESA Brochure, BR- In-flight releases showed unexpected velocities, that lead 323 (2015): 1-16. to undesired impact on the TM, and prevent its controllability and stabilisation. 5. F. Antonucci, M. Armano, H. Audley, G. Auger, M. A dedicated in-flight campaign of tests was carried out, Benedetti, P. Binetruy, J. Bogenstahl, D. Bortoluzzi, to explore the performance of the GPRM under different P. Bosetti, N. Brandt, M. Caleno, P. Caizares, A. working conditions. The release procedure was updated, Cavalleri, M. Cesa, M. Chmeissani, A. Conchillo, adding some phases to the standard manoeuvre. G. Congedo, I. Cristofolini, M. Cruise, K. Analysing in-flight data, focusing on the impulses Danzmann, F. D. Marchi, M. Diaz-Aguilo, I. received from the TM, it has been proved that the GPRM Diepholz, G. Dixon, R. Dolesi, N. Dunbar, J. Fauste, has not worked in nominal conditions. L. Ferraioli, V. Ferrone, W. Fichter, E. Fitzsimons, The TM received impulses at release from unexpected M. Freschi, A. G. Marin, C. G. Marirrodriga, R. impacts with the plungers. The impulse along the z Gerndt, L.Gesa, F. Gilbert, D. Giardini,C.Grimani, direction has been subdivided into two contributions: A. Grynagier, B. Guillaume, F. Guzmn, I. Harrison, - The contribution dependent on the net lateral G. Heinzel, V. Hernndez, M. Hewitson, D. push of the plunger, that produces also a z Hollington, J. Hough, D. Hoyland, M. Hueller, J. impulse due to the inclination of the contact Huesler, O. Jennrich, P. Jetzer, B. Johlander, N. zone. Karnesis, C. Killow, others, X. Llamas, I. Lloro, A. - The residual impulse generated by adhesion, Lobo, R. Maarschalkerweerd, S. Madden, D. delay asymmetry and probably other effects Mance, I. Mateos, P. W. McNamara, J. Mendes, E. (that cannot be predicted). Mitchell, A. Monsky, D. Nicolini, D. Nicolodi, M. The first contribution is the main one and produced the Nofrarias, F. Pedersen, M. Perreur-Lloyd, E. higher z velocity on the TM. The second contribution is Plagnol, P. Prat, G. D. Racca, J. Ramos-Castro, J. lower, and always produced controllable z velocity on the Reiche, J. A. R. Perez, D. Robertson, H. Rozemeijer, TM. J. Sanjuan,A. Schleicher,M. Schulte, D. Shaul, L. A possible explanation of the lateral push of the plungers Stagnaro, S. Strandmoe, F. Steier, T. J. Sumner, A. on the TM comes from the analysis of other in-flight data, Taylor, D. Texier, C. Trenkel, H.-B. Tu, S. Vitale, that showed some kind of bi-stable equilibrium of the G. Wanner, H. Ward, S. Waschke, P. Wass, W. J. plungers on the x-z plane (the one where most release Weber, T. Ziegler, and P. Zweifel, “The LISA impulses lie). pathfinder mission,” Classical Quantum Gravity, To summarise, high TM residual velocities are due to the vol. 29, no. 12, pp. 124014-1–124014-11, 2012. fact that the forces that arise at release are not the ones tested on-ground. 6. Armano, Michele & Audley, H & Baird, J & Further developments of this work will concentrate on Binetruy, P & Born, Míriam & Bortoluzzi, D & establishing what are all the possible causes that can lead Castelli, E & Cavalleri, A & Cesarini, Andrea & to unexpected contacts between TM and plungers. Cruise, A. M. & Danzmann, Karsten & de Deus Since the GPRM mechanism will be used in the future Silva, M & Diepholz, I & Dixon, G & Dolesi, R & coming mission LISA, the presented findings can be used Ferraioli, Luigi & Ferroni, Valerio & Fitzsimons, to improve its design and enhancing its performance. Enda & Freschi, M & Zweifel, Peter. (2018). Beyond the Required LISA Free-Fall Performance: 7. REFERENCES New LISA Pathfinder Results down to 20 μhz. 1. Bortoluzzi, D & Foulon, Bernard & García Physical Review Letters. 120. Marirrodriga, César & Lamarre, D. Object injection 10.1103/PhysRevLett.120.061101. in geodesic conditions: In-flight and on-ground testing issues. Advances in Space Research (2010). 7. P. M¨ausli, R. Romano, K. Lips, and P. Nellen, 1358-1379.10.1016/ j.asr.2010.01.023. “GPRM - Design description,” ESA, Frascati, Italy, ESA Internal Document S2-HTS-DDD-3001, 2007. 2. Staff of the Space Department, Staff of the Guidance and Control Laboratory A Satellite Freed of all but 8. Benedetti, M & Bortoluzzi, D & De Cecco, M. Gravitational Forces: “TRIAD I”, J. Spacecraft 11, (2007). A Momentum Transfer Measurement pp. 637–644, 1974. Experiment Between Contacting Bodies in the Presence of Adhesion Under Near-Zero Gravity Conditions. 10.1007/978-1-4020-6239-1_215. 3. Touboul, P., Foulon, B., Willemenot, E. Electrostatic space accelerometers for present and future missions, Acta Astronaut, 45, 605–617, 1999. 9. C. Zanoni and D. Bortoluzzi. Experimental- Analytical Qualification of a Piezoelectric Mechanism for a Critical Space Application.
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IEEE/ASME Transactions on Mechatronics 20.1 Institute for Fundamental Physics and Application / (2015): 427-437. INFN 5. Dipartimento di Fisica, Universitàdi Trento and 10. D. Bortoluzzi, J. W. Conklin, and C. Zanoni. Trento Institute for Fundamental Physics and Application / INFN, 38123 Povo, Trento, Italy Prediction of the LISA Pathfinder release 6. Istituto di Fotonica e Nanotecnologie, CNR- mechanism in-flight performance. Advances in Fondazione Bruno Kessler, I-38123 Povo, Trento, Space Research 51.7 (2013): 1145-1156. Italy 7. DISPEA, Universitàdi Urbino “Carlo Bo”, Via S. 11. D. Bortoluzzi et al. Injection of a Body into a Chiara, 27 61029 Urbino/INFN, Italy Geodesic: Lessons Learnt from the LISA Pathfinder 8. The School of Physics and Astronomy, University of Case, Aerospace Mechanism Symposium 2016, Birmingham, Birmingham, UK NASA/CP-2016-219090. 9. European Space Astronomy Centre, European Space Agency, Villanueva de la Ca˜nada, 28692 Madrid, Spain 12. C. Zanoni and D. Bortoluzzi. Experimental- 10. Institut fur Geophysik, ETH Zurich, Sonneggstrasse Analytical Qualification of a Piezoelectric 5, CH-8092, Zurich, Switzerland Mechanism for a Critical Space Application. 11. The UK Astronomy Technology Centre, Royal IEEE/ASME, Transactions on Mechatronics 20.1 Observatory, Edinburgh, Blackford Hill, Edinburgh, (2015): 427-437. EH9 3HJ, UK 12. Institut de Ciències de l1Espai (CSIC-IEEC), 13. I. Köker et al. Alignment and Testing of the GPRM Campus UAB, Carrer de Can Magrans s/n, 08193 Cerdanyola del Vallès, Spain as Part of the LTP Caging Mechanism. 15th 13. European Space Operations Centre, European European Space Mechanisms and Tribology Space Agency, 64293 Darmstadt, Germany Symposium. Vol. 718. 2013. 14. High Energy Physics Group, Physics Department, Imperial College London, Blackett Laboratory, 14. Jose Mendes. TM Release Experiments. ESA Prince Consort Road, London, SW7 2BW, UK internal document, 2017. 15. Department of Mechanical and Aerospace Engineering, MAE-A, P.O. Box 116250, University *LISA Pathfinder Collaboration - Dated: June 11, 2019 of Florida, Gainesville, Florida 32611, USA 16. Physik Institut, Universität Zurich, M Armano,1 H Audley,2 J Baird,3 P Binetruy,3, * M Born,2 D Winterthurerstrasse 190, CH-8057 Zurich, Bortoluzzi,4 E Castelli,5 A Cavalleri,6 A Cesarini,7 Switzerland A M Cruise,8 K Danzmann,2 M de Deus Silva,9 I Diepholz,2 17. SUPA, Institute for Gravitational Research, School G Dixon,8 R Dolesi,5 L Ferraioli,10 V Ferroni,5 of Physics and Astronomy, University of Glasgow, E D Fitzsimons,11 M Freschi,9 L Gesa,12 F Gibert,5 Glasgow, G12 8QQ, UK D Giardini,10 R Giusteri,5, † C Grimani,7 J Grzymisch,1 18. Department d1Enginyeria Electrônica, Universitat I Harrison,13 G Heinzel,2 M Hewitson,2 D Hollington,14 Politècnica de Catalunya, 08034 Barcelona, Spain D Hoyland,8 M Hueller,5 H Inchauspé,3, 15 O Jennrich,1 P 19. Gravitational Astrophysics Lab, NASA Goddard Jetzer,16 N Karnesis,3 B Kaune,2 N Korsakova,17 C J Killow,17 Space Flight Center, 8800 Greenbelt Road, J A Lobo,12, * I Lloro,12 L Liu,5 J P López-Zaragoza,12 Greenbelt, MD 20771 USA 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 *Deceased. M Nofrarias,12 S Paczkowski,2 M Perreur-Lloyd,17 †Current address: [email protected] 3 5 3 18 A Petiteau, P Pivato, E Plagnol, J Ramos-Castro, ‡[email protected] 2 17 12 5, ‡ J Reiche, DI Robertson, F Rivas, G Russano, 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
______Proc. 18. European Space Mechanisms and Tribology Symposium 2019, Munich, Germany, 18.-20. September 2019