# Pico-Sat to Ground Control: Optimizing Download Link via Laser Communication
## 5 Discussion and Future Work
Maintaining this range (formation flight) is yet another open question for the future [47]. The FSO uplink from the ground station to the satellite can be applied using a high-power laser on the ground station's side with low beam divergence and a 3-4 cm lens on the satellite's side; see [32]. We conjecture that by using few such lasercom pico-satellites, the true potential of the presented network can be explored via remote sensing observations by existing telescope-based observatories. The expected laser and RF communication radius of such pico-satellites is 1500 km (see Figure 11), allowing a theoretical coverage area of about \(4\times 10^{6}\) km\({}^{2}\). As the Earth's surface is about \(510\times 10^{6}\) km\({}^{2}\), a theoretical \"perfect-spread\" swarm of 128 pico-LEO satellites may cover the Earth. Naturally, the realistic number required for a global LEO swarm is larger--as the actual service radius of each satellite might be reduced to 1000 km and real-life layout of an LEO constellation requires a significant overlapping coverage. See [48; 49] for optimization considerations of large LEO constellations. Based on simulation and the use-case of Starlink (as of Q1 2022 they have over 1700 operational LEO satellites), a swarm of about 1000 such pico-satellites can support partial coverage of 20-40% of the globe; full global coverage can be achieved with 3000-5000 pico-satellites. All this can be achieved with the price tag of just a single \"real\" satellite (weighing around 1 ton). Naturally, there are many other open questions regarding the orbit optimization of the swarm and the regulation of strong lasers performing long-range FSO. Finally, the increasing popularity of new-space projects, combined with the reduction of the launch cost, leads to a growing number of nano-satellites. The demand for RF frequencies grows with every new satellite, which causes a bottleneck on the RF spectrum. Therefore, offloading satellite communication to FSO seems to be a natural solution [50]. The use of MEMS-mirrors to accurately aim an FSO laser in a sub-millisecond manner can enable a single nano-satellite to perform a time-divided communication with several FSO ground stations [51]. Naturally, implementing such a demanding system in a nano-satellite encapsulates several major research and engineering challenges. Yet, with the continuing improvement in the onboard computation capabilities and the miniaturization of key components such as ADCS and star-trackers [52], these technological barriers may be birched. We plan to follow this challenge with an annual new FSO pico-satellite. Our current model (named SATILA-2I [53]) is scheduled to be launched in Q1 2023, and is planned to have both a star-tracker and an ADCS, allowing it to perform initial FSO communication demonstrations. Conceptualization, B.B.-M.; Data curation, R.M. and B.B.-M.; Formal analysis, B.B.-M. and T.G. ; Funding acquisition, B.B.-M.; Investigation, R.M. ; Methodology, R.M., B.B.-M. and T.G. ; Project administration, B.B.-M. and T.G. ; Resources, B.B.-M.; Software, R.M. ; Supervision, B.B.-M. and T.G. ; Validation, B.B.-M. and T.G. ; Visualization, R.M. ; Writing--original draft, R.M., B.B.-M. and T.G. ; Writing--review & editing, B.B.-M. and T.G. All authors have read and agreed to the published version of the manuscript. This research was partially supported by the Ariel Cyber Innovation Center in conjunction with the Israel National Cyber Directorate in the Prime Minister's Office. Information regarding the SATILA projects can be found in the following google drive repository: [[https://photos.google.com/share/AFIQipNuD-Qzsa8](https://photos.google.com/share/AFIQipNuD-Qzsa8) XET7 KWuSVa6f79b01 jApVwpQga_scZwTrQtr3 iwMuicbA8 ISVKulgYkey=M2 UUnZZQZWlibzRXV1V0 BFj6 TnBSzzdWPHYtNTV3]([https://photos.google.com/share/AFIQipNuD-Qzsa8](https://photos.google.com/share/AFIQipNuD-Qzsa8) XET7 KWuSVa6f79b01 jApVwpQga_scZwTrQtr3 iwMuicbA8 ISVKulgYkey=M2 UUnZZQZWlibzRXV1V0 BFj6 TnBSzzdWPHYtNTV3).