In-orbit measurements of spacecraft microvibrations for satellite laser communication links

Abstract

Angular microvibrations of platform jitter on the optical interorbit communications engineering test satellite are measured in space during ground-to-satellite laser communication links. The microaccelerations are measured by the onboard accelerometers at a sampling rate of 2048 Hz. The angular microvibrations are estimated from the measured microaccelerations using the tracking characteristics of the laser communications terminal and the conversion factor on the basis of microvibration data obtained from ground-based tests. The power spectral density ͑PSD͒ of the satellite microvibrations is analyzed by using the fast Fourier transform analysis and the data length is examined according to the frequency resolution of the PSD. The in-orbit measurements of the PSDs are compared with those obtained from the ground test. The angular microvibrational base motion is estimated and a PSD up to 1024 Hz is additionally provided as a database of the real measurement results with previously obtained in-orbit measurements. The measured results will contribute to the angular jitter estimation and the design of a tracking control loop for space laser communication systems in the future.

Ultra-high-speed data relay systems

“…Therefore, the probability density function of the received optical power, due to only pointing errors, is given by [24] ( ) = −1 , 0 ≤ ≤ 1, 0 < < ∞. (12.4) where the parameter = 0 2 /(4 2 ) characterizes the random micro-vibrations of the user terminal; 0 being the laser bean radius at the transmitter, and = [∫ 2 ( ) ] 1/2 is the root-mean-square (RMS) of the random jitter [25]. To complete the model, a power spectral density (PSD) of the user terminal vibrations must be assumed, in order to take into account the temporal behavior of the transmitting telescope pointing errors.…”

“…As an estimation of the order of magnitude of the RMS random jitter , a quick overview of available literature shows that for LEO terminals is in the range of 20-45 μrad [25], and for an aircraft terminal few hundreds of microradians has been reported [27]. These figures refer to total amounts due to vibrations of the space-or aircraft, which are more relevant in the initial pointing and acquisition stages of the link, and usually compensated through a coarse pointing assembly.…”

Interplanetary laser communications and precision ranging

“…The host spacecraft platform's angular micro-vibrations, with frequencies spanning from less than 0.1 Hz to 100s of Hz (and amplitudes significantly larger than the transmit beam-width) are a major impediment to achieving the sub-μrad pointing requirement [50]. These micro-vibrations stem from guidance and control activities, such as momentum dumping and rocket firings.…”

Design of a Vibration Isolation System for the Space Telescope

“…As the successor to the HST, the James Webb Space Telescope with a 6.5 m diameter, might achieve a pointing stability of 0.004 arcsec [2]. However, the microvibrations due to the onboard equipment in spacecraft will seriously degrade the image quality of the space telescope [3]. The microvibration sources include control moment gyros, reaction wheel assemblies, cryocoolers, solar panel deployment actuators, and other motion devices [4].…”