# Design of Novel Laser Crosslink Systems Using Nanosatellites in Formation Flying: The VISION
###### Abstract  
With growth in data volume from space missions, interest in laser communications has increased, owing to their importance for high-speed data transfer in the commercial and defense fields, spaceborne remote sensing, and surveillance. Here, we propose a novel system for space-to-space laser communication, a very high-speed inter-satellite link system using an infrared optical terminal and nanosatellite (VISION), which is aimed at establishing and validating miniaturized laser crosslink systems and several space technologies using two 6U nanosatellites in formation flying. An optical link budget analysis is conducted to derive the signal-to-noise ratio requirements and allocate the system budget; the optical link margin should be greater than 10 dB to guarantee communication with practical limitations. The payload is a laser transceiver with a deployable space telescope to enhance the gain of the beam transmission and reception. Nanosatellites, including precise formation flying GNC systems, are designed and analyzed. The attitude control system ensures pointing and tracking errors within tens of arcsec, and they are equipped with a propulsion system that can change the inter-satellite distance rapidly and accurately. This novel concept of laser crosslink systems is expected to make a significant contribution to the future design and construction of high-speed space-to-space networks. laser crosslink; PAT (pointing, acquisition, and tracking); nanosatellite; formation flying Accepted: 1 August 2022  
Submitted: 3 August 2022  
**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. **Copyright:** © 2022 by the authors. Liconsee MDPI, Basel, Switzerland. 25-500 km [4]. As a part of the NASA Optical Communication and Sensor Demonstration (OCSD) program, AeroCube-7B/C demonstrated a precise pointing system with miniaturized actuators and sensors for laser crosslinks [5]. Furthermore, the laser interconnect and networking communications system (LINCS)-A/B was developed to demonstrate laser communication technologies with a data rate of 5 Gbps at an inter-satellite distance of 2000 km [6]. Inter-satellite laser communication requires precise formation flying technologies, such as relative navigation and pointing maneuvers. Canadian Advanced Nanospace eXperiment-4&5 (CANX-4&5), developed by UTIAS/SFL, demonstrated autonomous formation flying technologies, including relative navigation and positioning maneuvers [7]. Gomspace eXperiment-4A&B (GomX-4A&B), led by GomSpace, demonstrated RF crosslink technology and implemented orbit maneuvers by changing the inter-satellite distances using a cold-gas propulsion system [8]. Yonsei University has developed CubeSat Astronomy by NASA and Yonsei using Virtual ALignment-eXperiment/Coronagraph (CANYVAL-X/C) to study the core technologies of a virtual space telescope based on autonomous formation flying [9]. To implement the laser crosslink and demonstrate several space technologies, we propose the very high-speed inter-satellite link system using infrared optical terminal and nanosatellite (VISION) mission. This study is aimed at establishing and validating high-speed and miniaturized laser crosslink systems using two 6U nanosatellites in formation flying, termed as Altair and Vega. The final goal is to achieve a data rate of 1 Gbps with a coded bit error rate (BER) of less than \(1\times 10^{-9}\) at an inter-satellite distance of 1000 km. Figure 1 presents a conceptual illustration of the VISION mission. The total system has half the mass and size of the LINCS system [6], with similar performances for the laser crosslink. The mission payload of the laser communication terminal (LCT) is equipped with deployable segmented front-end optics (FEO), which enhances the gain of beam transmission and reception relevant to a large aperture. The proposed deployable optics can be applied to high-resolution Earth observation payloads with miniaturization and mass reduction.