# Pico-Sat to Ground Control: Optimizing Download Link via Laser Communication
### Related Work  
FSO communication involves the use of modulated optical (laser) beams to send telecommunication information through the atmosphere. The concept of light communication is not new, and was first introduced by [PERSON] in 1880, who \begin{table}
\begin{tabular}{l l l l l l l} \hline \hline  & \multicolumn{3}{c}{**Nano-Satellite Communication: RF vs. Laser**} \\ \hline Category & UHF & S-Band & X-Band & Ka & 1550 nm & 1064 nm \\ \hline Bit rate (Mbps) & 0.01 & 0.5 & 5 & 20 & 1000 & 50 \\ \hline Free to use & no & no & no & no & yes & yes \\ Suitable for 1 U & yes & yes & so so & so so & yes & yes \\ Tx beam (deg) & 90 & 30 & 10 & 3 & 0.1 & 0.05 \\ All weather & yes & so so & yes & so so & so & no \\ Project Example & Norby & GOMX3 & GOMX3 & NLSSAT & CLICK * & AC 7-B \\ \hline \hline \end{tabular}  
* The CLICK demonstration nano-satellite is scheduled to be launched on 2023; all the other nano-satellites are “in orbit”.  
\end{table} 
Table 1: Communication technologies related to nano-satellites. Figure 1: A general illustration of the satellite–terrestrial FSO communication resource allocation and scheduling model. On the (**left** side), a ground station’s point of view is presented: the orange telescope should be aligned to one of the four (green) nano-satellites. On the (**right** side), a nano-satellite’s point of view is shown: it should point to one of the five (red) ground stations. demonstrated the use of an intensity-modulated optical beam to transmit telephone signals through the air to a distant receiver [2]. Over the last two decades, wide-band FSO links have been considered as a back-hauling technology for terrestrial and urban networks, mainly in cases where fiber optics and RF communication links are not applicable [3, 4]. Fixed FSO links between buildings have long been established and form a separate commercial product segment in local and metropolitan area networks [5, 6]. However, the mobile and long-range applications of this technology are aggravated by extreme requirements for pointing and tracking, due to the small optical beam divergences of FSO. Aside from the noted challenge of accurate pointing, long-haul FSO links have notable disadvantages related to the fading effect, dispersion, and signal obstruction due to weather and atmospheric conditions [7, 8]. Motivated by the Optical Communications and Sensors Demonstration (OCSD) by NASA using 1.5 U nano-satellite demonstrations [9], which presented a 50-100 Mbps laser link with sub \(10^{-6}\) bit error rate (without forward error correction), this paper presents a \"best-effort\" dynamic network framework. Thus, we assume clear-sky conditions. For comprehensive studies regarding \"all-weather\" FSO communication, see [2, 5, 7, 8]. A dynamic FSO link (e.g., between a drone and an FSO ground station) suggests a major tracking challenge. Moreover, generalizing FSO links to an FSO network raises several problems regarding optimal topology and routing. To this end, NASA is launching an advanced laser communication experiment, termed Laser Communications Relay Demonstration (LCRD). The experiment will use NASA's ground stations and satellites with a payload designed to test such communication in terms of quality and atmospheric effect. The primary end-goal motivation of the project is to enable capturing high-definition data such as 4K video from space [10]. [PERSON] et al. [11] described a ground station distributor for communication networks that involve satellites and unmanned aerial vehicles (UAVs). They suggested a hybrid FSO/RF communication model, in which a ground station receives satellite data using FSO communication and distributes them using RF communication to the end-users (UAVs). [PERSON] et al. [12] proposed to use high-altitude platforms as relays in the communication between satellites and vehicles (either aerial or ground). Their suggested dynamic network is based on quantum key distribution (QKD) and FSO communication.