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Laser communications can enable more efficient and higher bandwidth communications across longer distances than conventional radio frequency (RF) systems. However, beam divergence angles for laser systems are narrower than typical RF systems, and require precise pointing, acquisition, and tracking systems to establish and maintain the link. In addition, typical lasercom links are point-to-point, and not capable of multicast or broadcast. Conventional pointing and tracking (PAT) systems use mechanical gimbals or fast-steering mirrors. Mechanical gimbals may not meet the size, weight, and power (SWaP) constraints for small spacecraft, particularly for multiple concurrent spatially diverse beams. Fast-steering mirrors while compact and efficient have limited aperture size, and many would be needed to provide multiple links over a hemisphere. The Miniature Optical Steered Antenna for Intersatellite Communications (MOSAIC) aims to provide nonmechanical pointing and tracking using liquid lenses, allowing a wide field-of-view and support for multiple concurrent links. Initial work with commercially available liquid lenses showed that liquid lenses can be used in a space environment and assessed spatial coverage. In this work, we model a transmitter using three liquid lenses. One on-axis lens provides focusing capability. Two off-axis and perpendicular lenses provide beam steering, with a fisheye lens amplifying the effect. This provides near-hemispherical pointing up to 170 degrees. We investigate beam quality and divergence using a Zemax model and conduct a link analysis dependent on the beam steering angle and rotation angle. A 25 Mbps link with 200 mW transmit power at 1550 nm (optical C band) and 16-ary pulse position modulation (16-PPM) can be maintained up to 28 km separation with 3 dB margin for an Optotune EL-16-40-TC liquid lens. Losses are primarily due to the liquid lenses limiting aperture size to 16 mm. We also consider the impact of diffusers for increasing numerical aperture through a simple ray transfer analysis and experimental results.
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