<title>System requirements for a deep-space optical transceiver</title>

Abstract

The functional requirements and design drivers for an Optical Communications subsystem are assessed based on the system requirements imposed by a proposed Europa Orbiter mission. Unlike near-Earth optical communications systems, deep space missions impose a unique set of requirements that drives the subsystem design. Significant challenges on laser efficiency, thermal control, pointing and tracking, stray/scatter light control, and subsystem mass/power need to be addressed for a successful subsystem implementation. The baseline design concept for a lasercom subsystem for the Europa orbiter mission employs a 30-cm diameter, diffraction-limited telescope, and a diode pumped solid state laser operating at 1 .06 pin to support downlink communications. The baseline pointing and tracking approach is to perform Earth Image tracking with occasional calibration using the Earth-moon or Earth-star images. At high phase angles when the Earth image does not provide sufficient brightness for high rate tracking, inertial sensors (accelerometers) measurements are used to propagate the knowledge of the optical boresight at a higher rate in between celestial reference updates. Additionally, uplink beacon tracking will be used to support pointing at short range and near solar opposition when Earth image along does not provide sufficient signal power for tracking.

Adaptive power control for satellite to ground laser communication

“…These features include extremely wide bandwidth, significantly smaller beam divergence angle, smaller aperture diameter and lower weight equipment to be carried by the satellite platform [1][2][3][4].…”

“…Satellite laser communication has several unique physical features, which enable it to achieve a better system performance, as compared to traditional radio communication. These features include extremely wide bandwidth, significantly smaller beam divergence angle, smaller aperture diameter and lower weight equipment to be carried by the satellite platform [1][2][3][4].…”

“…The downlink laser intensity is restricted due to the satellite platform power supply capabilities and eye safety requirements [2,6].…”

Acquisition Time for Ground-to-Satellite Optical Communication System in Weak Atmospheric Turbulence with Spatial Diversity

“…Then, using Eq. (7), the required beam divergence is calculated for a given receiver diameter ranging from 15 to 30 cm for a space-borne receiver [13]. Finally, the acquisition time is calculated using Eq.…”

<title>Pointing accuracy improvement using model-based noise reduction method</title>

“…A recent study shows that the centroid error (random and bias error) for deep space optical communications needs to be less than 1/20 th pixel whereas the total pointing error allowed (1 sigma) is 1/15 th pixel [4,5]. Two types of centroid errors, random and bias, are affected by various sources.…”