6,910 research outputs found
Nano-Newton electrostatic force actuators for femto-Newton-sensitive measurements: System performance test in the LISA Pathfinder mission
No full textLISA Pathfinder Collaboration: et al.Electrostatic force actuation is a key component of the system of geodesic reference test masses (TM) for the LISA orbiting gravitational wave observatory and in particular for performance at low frequencies, below 1 mHz, where the observatory sensitivity is limited by stray force noise. The system needs to apply forces of order 10−9 N while limiting fluctuations in the measurement band to levels approaching 10−15 N/Hz1/2. We present here the LISA actuation system design, based on audio-frequency voltage carrier signals, and results of its in-flight performance test with the LISA Pathfinder test mission. In LISA, TM force actuation is used to align the otherwise free-falling TM to the spacecraft-mounted optical metrology system, without any forcing along the critical gravitational wave-sensitive interferometry axes. In LISA Pathfinder, on the other hand, the actuation was used also to stabilize the TM along the critical axis joining the two TM, with the commanded actuation force entering directly into the mission’s main differential acceleration science observable. The mission allowed demonstration of the full compatibility of the electrostatic actuation system with the LISA observatory requirements, including dedicated measurement campaigns to amplify, isolate, and quantify the two main force noise contributions from the actuation system, from actuator gain noise and from low frequency “in band” voltage fluctuations. These campaigns have shown actuation force noise to be a relevant, but not dominant, noise source in LISA Pathfinder and have allowed performance projections for the conditions expected in the LISA mission.This work has been made possible by the LISA Pathfinder mission, which is part of the space-science program of the European Space Agency. We acknowledge the work of the prime contractor for LPF and for the “LISA Technology Package,” Airbus Defense and Space, for the industrial implementation of the electrostatic actuation suspension as part of the overall DFACS dynamic control under their responsibility. The Italian contribution has been supported by Istituto Nazionale di Fisica Nucleare (INFN) and Agenzia Spaziale Italiana (ASI), Project No. 2017-29-H.1-2020 “Attivit`a per la fase A della missione LISA.” The UK groups wish to acknowledge support from the United Kingdom Space Agency (UKSA), the Scottish Universities Physics Alliance (SUPA), the University of Glasgow, the University of Birmingham, and Imperial College London. The Swiss contribution acknowledges the support of the Swiss Space Office via the PRODEX
Programme of ESA, the support of the ETH Research Grant No. ETH-05 16-2 and the support of the Swiss National Science Foundation (Projects No. 162449 and No. 185051). The Albert Einstein Institute acknowledges the support of the German Space Agency, DLR. The work is supported by the Federal Ministry for Economic Affairs and Energy based on a resolution of the German Bundestag (No. FKZ 50OQ0501, No. FKZ 50OQ1601, and No. FKZ 50OQ1801). J. I. T. and J. S. acknowledge the support of the U.S. National Aeronautics and Space Administration (NASA). Spanish contribution has been supported by Contracts No. AYA2010-15709 (Ministerio de Ciencia e Innovación, MICINN), No. ESP2013-47637-P, No. ESP2015-67234-P, No. ESP2017-90084-P (Ministerio de Asuntos Económicos y Transformación Digital, MINECO), and No. PID2019–106515GB-I00 (MICINN). Support from AGAUR (Generalitat de Catalunya) Contract No. 2017-SGR-1469 is also acknowledged. M. N. acknowledges support from Fundacion General CSIC (Programa ComFuturo). F. R. acknowledges an FPI contract from MINECO. The French contribution has been supported by the CNES (Accord Specific de Project No. CNES 1316634/CNRS 103747), the CNRS, the Observatoire de Paris and the University Paris-Diderot. E. P. and H. I. would also like to acknowledge the financial support of the UnivEarthS Labex program at Sorbonne Paris Cit´e (No. ANR-10-LABX-0023 and No. ANR-11-IDEX-0005-02). N. K. would like to thank for the support
from the CNES Fellowship.Peer reviewe
NanoNewton electrostatic force actuators for femtoNewton-sensitive measurements: system performance test in the LISA Pathfinder mission
No full textInternational audienceElectrostatic force actuation is a key component of the system of geodesic reference test masses (TM) for the LISA orbiting gravitational wave observatory and in particular for performance at low frequencies, below 1 mHz, where the observatory sensitivity is limited by stray force noise. The system needs to apply forces of order 10 N while limiting fluctuations in the measurement band to levels approaching 10 N/Hz. We present here the LISA actuation system design, based on audio-frequency voltage carrier signals, and results of its in-flight performance test with the LISA Pathfinder test mission. In LISA, TM force actuation is used to align the otherwise free-falling TM to the spacecraft-mounted optical metrology system, without any forcing along the critical gravitational wave-sensitive interferometry axes. In LISA Pathfinder, on the other hand, the actuation was used also to stabilize the TM along the critical axis joining the two TM, with the commanded actuation force entering directly into the mission's main differential acceleration science observable. The mission allowed demonstration of the full compatibility of the electrostatic actuation system with the LISA observatory requirements, including dedicated measurement campaigns to amplify, isolate, and quantify the two main force noise contributions from the actuation system, from actuator gain noise and from low frequency ``in band'' voltage fluctuations. These campaigns have shown actuation force noise to be a relevant, but not dominant, noise source in LISA Pathfinder and have allowed performance projections for the conditions expected in the LISA mission
NanoNewton electrostatic force actuators for femtoNewton-sensitive measurements: system performance test in the LISA Pathfinder mission
No full textElectrostatic force actuation is a key component of the system of geodesic
reference test masses (TM) for the LISA orbiting gravitational wave observatory
and in particular for performance at low frequencies, below 1 mHz, where the
observatory sensitivity is limited by stray force noise. The system needs to
apply forces of order 10 N while limiting fluctuations in the
measurement band to levels approaching 10 N/Hz. We present here
the LISA actuation system design, based on audio-frequency voltage carrier
signals, and results of its in-flight performance test with the LISA Pathfinder
test mission. In LISA, TM force actuation is used to align the otherwise
free-falling TM to the spacecraft-mounted optical metrology system, without any
forcing along the critical gravitational wave-sensitive interferometry axes. In
LISA Pathfinder, on the other hand, the actuation was used also to stabilize
the TM along the critical axis joining the two TM, with the commanded
actuation force entering directly into the mission's main differential
acceleration science observable. The mission allowed demonstration of the full
compatibility of the electrostatic actuation system with the LISA observatory
requirements, including dedicated measurement campaigns to amplify, isolate,
and quantify the two main force noise contributions from the actuation system,
from actuator gain noise and from low frequency ``in band'' voltage
fluctuations. These campaigns have shown actuation force noise to be a
relevant, but not dominant, noise source in LISA Pathfinder and have allowed
performance projections for the conditions expected in the LISA mission
Nano-Newton electrostatic force actuators for femto-Newton-sensitive measurements: system performance test in the LISA Pathfinder mission
No full textElectrostatic force actuation is a key component of the system of geodesic reference test masses (TM) for the LISA orbiting gravitational wave observatory and in particular for performance at low frequencies, below 1 mHz, where the observatory sensitivity is limited by stray force noise. The system needs to apply forces of order 10-9¿¿N while limiting fluctuations in the measurement band to levels approaching 10-15¿¿N/Hz1/2. We present here the LISA actuation system design, based on audio-frequency voltage carrier signals, and results of its in-flight performance test with the LISA Pathfinder test mission. In LISA, TM force actuation is used to align the otherwise free-falling TM to the spacecraft-mounted optical metrology system, without any forcing along the critical gravitational wave-sensitive interferometry axes. In LISA Pathfinder, on the other hand, the actuation was used also to stabilize the TM along the critical ¿ axis joining the two TM, with the commanded actuation force entering directly into the mission’s main differential acceleration science observable. The mission allowed demonstration of the full compatibility of the electrostatic actuation system with the LISA observatory requirements, including dedicated measurement campaigns to amplify, isolate, and quantify the two main force noise contributions from the actuation system, from actuator gain noise and from low frequency “in band” voltage fluctuations. These campaigns have shown actuation force noise to be a relevant, but not dominant, noise source in LISA Pathfinder and have allowed performance projections for the conditions expected in the LISA mission.Peer ReviewedPostprint (author's final draft
Direct force measurements for testing the LISA Pathfinder gravitational reference sensor
No full textWe present results of testing of the LISA Pathfinder gravitational reference sensor (GRS) using a 4-test-mass torsion pendulum facility aimed at measuring low-frequency force-noise sources in the LISA and LISA Pathfinder frequency band. This pendulum, for the first time, allows us to make measurements which are sensitive to all forces acting along the sensitive axis of the test mass, not only those that create a torque. We will report on a campaign of testing using the LISA Pathfinder 'engineering model' prototype GRS which has set upper limits on the overall force noise acting on the test mass contributed by surface effects within the sensor at a level of 100 fN Hz-1/2 at 2 mHz and measured specific sources of unwanted disturbances. These sources include forces arising from the electrostatic coupling between the sensor and test-mass motion, electrostatic fields due to surface-potential variations and thermal-gradient effects within the sensor. Finally, we describe the extension of this campaign to the LISA Pathfinder flight-model replica GRS which will be crucial in verifying the design and performance of the flight instrument
Beyond the required LISA free-fall performance: new LISA pathfinder results down to 20 mu Hz
No full textIn the months since the publication of the first results, the noise performance of LISA Pathfinder has improved because of reduced Brownian noise due to the continued decrease in pressure around the test masses, from a better correction of noninertial effects, and from a better calibration of the electrostatic force actuation. In addition, the availability of numerous long noise measurement runs, during which no perturbation is purposely applied to the test masses, has allowed the measurement of noise with good statistics down to 20¿¿µHz. The Letter presents the measured differential acceleration noise figure, which is at (1.74±0.05)¿¿fm¿s-2/vHz above 2 mHz and (6±1)×10¿¿fm¿s-2/vHz at 20¿¿µHz, and discusses the physical sources for the measured noise. This performance provides an experimental benchmark demonstrating the ability to realize the low-frequency science potential of the LISA mission, recently selected by the European Space Agency.Peer ReviewedPostprint (published version
Charge-induced force noise on free-falling test masses: results from LISA Pathfinder
No full textWe report on electrostatic measurements made on board the European Space Agency mission
LISA Pathfinder. Detailed measurements of the charge-induced electrostatic forces exerted on freefalling
test masses (TMs) inside the capacitive gravitational reference sensor are the first made in a
relevant environment for a space-based gravitational wave detector. Employing a combination of
charge control and electric-field compensation, we show that the level of charge-induced
acceleration noise on a single TM can be maintained at a level close to 1.0 fm s−2 Hz−1=2 across
the 0.1–100 mHz frequency band that is crucial to an observatory such as the Laser Interferometer
Space Antenna (LISA). Using dedicated measurements that detect these effects in the differential
acceleration between the two test masses, we resolve the stochastic nature of the TM charge
buildup due to interplanetary cosmic rays and the TM charge-to-force coupling through stray electric fields in the sensor. All our measurements are in good agreement with predictions based on
a relatively simple electrostatic model of the LISA Pathfinder instrument
Lisa M. Parsons: Hall of Fame Inductee
No full textLisa M. Parsons: Hall of Fame Inductee
Lisa M. Parsons does not have to take a back set to anyone when it comes to playing basketball at Winona State University. She was a dominating inside force for the Warriors during her collegiate career that eventually led to selections on four all-conference teams and honorable mention All-American NAIA honors.
Parsons’ numbers prove her dominance in the game of basketball. She is the Warriors’ all-time leading rebounder and stands in second place in scoring. The 562 points she scored in the 1989-90 season still ranks first for single-season ranks, third all-time.
There have been only nine seasons where a Warrior has grabbed 200 or more rebounds and Parsons accomplished the feat in three of those seasons.
Parsons is the only WSU player to have recorded 20 rebounds in a game and four times she scored 30 or more points with a career-high 33, ranking third among all-time single-game efforts.
Defensively, Parsons ranks as one of only two WSU players to have 100 or more blocked shots and her 170 career blocks is second best all-time.
Since her graduation from Winona State in 1992, Parsons has gone to a basketball coaching career. She was an assistant coach for two years at Anoka, MN High School before holding the head coaching position at the University of Dubuque. Today, Parsons is the head coach at Hamline University, a position she has held since 1999.https://openriver.winona.edu/halloffameinductees/1052/thumbnail.jp
First in the Nation in Education : Final Report,1984.
No full textThis report is one step in an ongoing process of change and is a plea for commitment for high standards in education in Iowa. Contains the final reports of the six subcommittees as adopted by the Excellence in Education Task Force, and the five recommendations made by the Task Force
Nano-Newton electrostatic force actuators for femto-Newton-sensitive measurements: System performance test in the LISA Pathfinder mission
No full textElectrostatic force actuation is a key component of the system of geodesic reference test masses (TM) for the LISA orbiting gravitational wave observatory and in particular for performance at low frequencies, below 1 mHz, where the observatory sensitivity is limited by stray force noise. The system needs to apply forces of order 10⁻⁹ N while limiting fluctuations in the measurement band to levels approaching 10⁻¹⁵ N/H¹/² We present here the LISA actuation system design, based on audio-frequency voltage carrier signals, and results of its in-flight performance test with the LISA Pathfinder test mission. In LISA, TM force actuation is used to align the otherwise free-falling TM to the spacecraft-mounted optical metrology system, without any forcing along the critical gravitational wave-sensitive interferometry axes. In LISA Pathfinder, on the other hand, the actuation was used also to stabilize the TM along the critical x axis joining the two TM, with the commanded actuation force entering directly into the mission's main differential acceleration science observable. The mission allowed demonstration of the full compatibility of the electrostatic actuation system with the LISA observatory requirements, including dedicated measurement campaigns to amplify, isolate, and quantify the two main force noise contributions from the actuation system, from actuator gain noise and from low frequency "in band" voltage fluctuations. These campaigns have shown actuation force noise to be a relevant, but not dominant, noise source in LISA Pathfinder and have allowed performance projections for the conditions expected in the LISA mission.This work has been made possible by the LISA Pathfinder mission, which is part of the space-science program of the European Space Agency. We acknowledge the work of the prime contractor for LPF and for the “LISA Technology Package,” Airbus Defense and Space, for the industrial implementation of the electrostatic actuation suspension as part of the overall DFACS dynamic control under their responsibility. The Italian contribution has been supported by Istituto Nazionale di Fisica Nucleare (INFN) and Agenzia Spaziale Italiana (ASI), Project No. 2017-29-H.1-2020 “Attività per la fase A della missione LISA.” The UK groups wish to acknowledge support from the United Kingdom Space Agency (UKSA), the Scottish Universities Physics Alliance (SUPA), the University of Glasgow, the University of Birmingham, and Imperial College London. The Swiss contribution acknowledges the support of the Swiss Space Office via the PRODEX Programme of ESA, the support of the ETH Research Grant No. ETH-05 16-2 and the support of the Swiss National Science Foundation (Projects No. 162449 and No. 185051). The Albert Einstein Institute acknowledges the support of the German Space Agency, DLR. The work is supported by the Federal Ministry for Economic Affairs and Energy based on a resolution of the German Bundestag (No. FKZ 50OQ0501, No. FKZ 50OQ1601, and No. FKZ 50OQ1801). J.?I.?T. and J.?S. acknowledge the support of the U.S. National Aeronautics and Space Administration (NASA). Spanish contribution has been supported by Contracts No. AYA2010-15709 (Ministerio de Ciencia e Innovación, MICINN), No. ESP2013-47637-P, No. ESP2015-67234-P, No. ESP2017-90084-P (Ministerio de Asuntos Económicos y Transformación Digital, MINECO), and No. PID2019–106515GB-I00 (MICINN). Support from AGAUR (Generalitat de Catalunya) Contract No. 2017-SGR-1469 is also acknowledged. M.?N. acknowledges support from Fundacion General CSIC (Programa ComFuturo). F.?R. acknowledges an FPI contract from MINECO. The French contribution has been supported by the CNES (Accord Specific de Project No. CNES 1316634/CNRS 103747), the CNRS, the Observatoire de Paris and the University Paris-Diderot. E.?P. and H.?I. would also like to acknowledge the financial support of the UnivEarthS Labex program at Sorbonne Paris Cité (No. ANR-10-LABX-0023 and No. ANR-11-IDEX-0005-02). N.?K. would like to thank for the support from the CNES Fellowship.https://journals.aps.org/prd/abstract/10.1103/PhysRevD.109.10200
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