The LISA Technology Package (LTP) aboard of LISA pathfinder mission is dedicated to demonstrate and verify key technologies for LISA, in particular drag free control, ultra-precise laser interferometry and gravitational sensors. Two inertial sensors, the optical interferometry in between combined with the dimensional stable Glass ceramic Zerodur structure are setting up the LTP. The validation of drag free operation of the spacecraft is planned by measuring laser interferometrically the relative displacement and tilt between two test masses (and the optical bench) with a noise levels of 10 pm/V'i and 10 nrad/v"i between 3 mHz and 30 mHz. This performance and additionally overall environmental tests was currently verified on EM level. The OB structure is able to support two inertial sensors (17kg each) and to withstand 25 g design loads as well as 0 . . . 40°C temperature range. Optical functionality was verified successfully after environmental tests. The engineering model development and manufacturing of the optical bench and interferometry hardware and their verification tests will be presented.
A model is presented for predicting source levels and beam patterns generated by parametric acoustic sources of rectangular aperture. This model is a generalization of a previous model for square and circular apertures [J. Acoust. Soc. Am. 61, 325–337 (1977)]. Because the nonlinear absorption of the primary beams is less for a rectangular projector than for a square projector of equal area and primary source level, it is possible to obtain larger difference-frequency source levels from rectangular projectors than from their square (or circular) couterparts. The conditions required for such enhanced source levels are discussed, and the results of an experimental test of the model are presented.
Experimental results of intensities and beam patterns of a parametric sonar transmitting array are presented. For a mean primary frequency of 720 kHz and secondary frequency of 50 kHz, source levels up to 90 dB re 1 μbar at 1 m are attainable. At this level, however, saturation effects broaden the beamwidth to 8°, whereas the unsaturated condition produces a beam width of 3°.
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