Steven Griffin, The Boeing Company; David Gerwe, The Boeing Company; Jacob Lucas, The Boeing Company
Keywords: Vibrometry, satellites
Abstract:
Vibrometry of objects at extended ranges poses several interesting challenges. Typical vibrometry use has the instrument measuring the motion from a small area over which it can safely be assumed that there is no velocity gradient. This assumption cannot hold true when preforming vibration measurements over the extended ranges involved in terrestrial vibrometry of a satellite. At extended ranges the area over which vibration is being measured could encompass the entire satellite, allowing for significant velocity gradients across the measurement area. In addition to this, there are speckle effects caused by the passage of the measurement beam through the atmosphere. This can result in dynamic preferential illumination of the satellite. This paper explores the viability of recovering meaningful vibrometry data from an object when the measurement beam is of the order of the target size. Additionally, determining if heterodyne systems have utility as tools with which to measure satellite vibration. Included is simulated data with and without atmosphere, and lab data measured with a scaled model. The simulated and experimental results both indicate that full illumination of an object does not preclude vibrometry measurement. Additionally the simulated data implies that heterodyne systems could be used as long-range vibrometers. The utility of these measurements given the area of the measurement beam at such distances is limited, but the experimental data shown here indicates that different motion modes can be discerned with the beam held static over the target, e.g. in phase vs. out of phase panel vibration. Rastering the beam over the target could allow for vibration measurements of various satellite features individually, despite far field spot size limitations. While further investigation into SNR lower bounds and more rigorous simulation of object motion would better indicate expected performance, all current data indicates that terrestrial measurement of satellite vibration with existing systems could provide meaningful data about the target.
Date of Conference: September 11-14, 2018
Track: Non-Resolved Object Characterization