Extremely stable piezo mechanisms for the new gravitational wave observatory

Abstract

Abstract-Detection and observation of gravitational waves requires extreme stability in the frequency range 3e-5 Hz to 1 Hz. NGO/LISA will attain this by creating a giant interferometer in space, based on free floating proof masses in three spacecrafts.To operate NGO/LISA, the following piezo mechanisms are developed: 1.A piezo stack mechanism (Point Angle Ahead Mechanism)Due to time delay in the interferometer arms, the beam angle needs to be corrected. A mechanism rotating a mirror with a piezo stack performs this task. The critical requirements are the contribution to the optical path difference (less than 1.4 pm/ Hz) and the angular jitter (less than 8 nrad/ Hz). 2.A piezo sliding mechanism (Fiber Switching Unit Actuator)To switch from primary to the redundant laser source, a Fiber Switching Unit Actuator (FSUA) is developed. The critical requirements are the coalignment of outgoing beams of <+/-1 micro radian and <+/-1 micro meter. A redundant piezo sliding mechanism rotates a wave plate over 45 degrees. 3.A piezo stepping mechanism (In Field Pointing Mechanism) Due to seasonal orbit evolution effects, beams have to be corrected over a stroke of +/-2.5 degrees. The critical requirements are the contribution to the optical path difference (less than 3.0 pm/ Hz) and the angular jitter (less than 1 nrad/ Hz). Due to the large stroke, a piezo stepping concept was selected. Dedicated control algorithms have been implemented to achieve these challenging requirements. This paper gives description of the designs and the ongoing process of qualifying the mechanisms for space applications.

Design of a Large-Range Compliant Rotary Micropositioning Stage With Angle and Torque Sensing

“…For example, the compliant rotary stage with 10°range can be applied in optical scanning applications [32] and laser beam pointing in space applications [33]. In the further research, a more compact rotary stage will be produced by resorting to an optimum architectural design.…”

A fast steering mirror with ultra-low geometric tilt-to-length coupling noise for space-borne gravitational wave detection

“…Compared with the traditional pointing mechanism, the pointing mechanism of space-borne gravitational wave detection needs to be able to achieve a larger rotation range, higher precision, higher stability pointing, and ultra-low speed tracking in the same time. LISA (Laser Interferometer Space Antenna) proposed two kinds of pointing schemes, called telescope articulation and in-field pointing [3][4][5][6][7][8][9].…”

Design and Thermal Stability Analysis of Swing Micro-Mirror Structure for Gravitational Wave Observatory in Space

“…In addition, the European Space Agency is building a gravitational wave detector, eLISA, to detect low-frequency gravitational waves in space [3]. Any path length changes measured by eLISA's interferometer arms can be attributed to the effect of gravitational waves, which proves the detection of gravitational waves [4]. EADS Astrium proposed a kind of alternative payload architecture for eLISA and proved that it was feasible to use payload architecture with only one active proof mass per spacecraft [5].…”

“…Researchers from the TNO Opto-mechatronics Department, Netherlands, have designed an In-field Pointer Mechanism for eLISA gravitational wave detector. They tested the pointing jitter of the mechanism while the actuator was in motion but did not test its thermal stability [4,7].…”

“…The first-order natural frequency is greater than 80 Hz. Due to the effect of mechanical vibration, space thermal radiation, and other disturbances in space, the relative position of each part of the swing micro-mirror structure will change slightly, and the outgoing light angles will change accordingly [4]. Therefore, it is necessary that the mechanism can automatically correct the reflection angle of the mirror to meet the requirement of light transfer.…”