On-Orbit Measurement Of Iss Vibrations During Opals Extended Mission Operations

Detailed understanding of the International Space Station vibration environment, particularly for the unpressurized portions of the platform, is and has been of high interest to payload developers seeking precision pointing performance due to its potential impact on on-orbit operations. The availability of such information, however, especially measured data, has been scarce, usually forcing investigators to utilize conservative bounding assumptions.During extended mission operations aboard the ISS at ELC 1, FRAM 8, the OPALS payload conducted a series of experiments aimed at improving the understanding of this key environmental parameter. The payload was repurposed for performing open-loop tracking of a ground-based laser beacon in a step-and-stare fashion so as to minimize the effects of its own gimbal on the measurement. Following significant processing of data acquired at 100Hz, the root-mean-square jitter at the OPALS mounting location is estimated to be in the 20-30 microradians range, and may even be in the low teens under certain conditions, an order of magnitude lower than previously assumed value.