# Pico-Sat to Ground Control: Optimizing Download Link via Laser Communication
## 5 Discussion and Future Work  
This paper introduced a new concept of FSO network for nano-satellites from the points of view of both the ground station and the satellite. The actual design concepts of an FSO pico-satellite (named SATLLA-2B, 2P, 300 g, see Figure 4) and a corresponding optical ground station were presented in Section 2. On 13 January 2022, SATLLA-2B was successfully launched into LEO orbit and is currently operational. The scheduling problem that we discussed in Section 3 is from the viewpoint of the ground station. The same model can be applied from the point of view of the satellite that searches for ground stations to communicate with; thus, the problems are dual. Each such side of the problem is one-to-many. However, the full-scale problem is many-to-many, as it consists of many satellites that need to communicate with many ground stations. Such a problem is obviously harder than the one-to-many versions. Nevertheless, we believe that bio-inspired algorithms can serve as a good solution for such complex problems, due  
Figure 11: Early experiments with the recently launched SATLLA-2B pico-satellite. Using the TinyGS project, ground stations can receive and share RF data transmitted by LoRa based satellites. In this image, about 30 ground stations are receiving an RF beacon transmitted by SATLLA-2B (in a distance range of 550–2100 km). The ground stations marked in green received the beacon properly, while the brown one received CRC error; SATLLA-2B is marked in blue. to their robustness to model variations and their ability to handle large-scale problems. For example, an ant colony algorithm has been recently proposed for a related problem of network formation for FSO satellite communication [46]. The massive growth in the number of commercial and research satellites is leading to a frequency demand on the already limited RF spectrum. In order to support large sets of satellite constellations while reducing the usage of the RF spectrum, we propose the following satellite communication framework:  
1. Most satellites will not communicate directly with Earth, but will instead use ISM channels (e.g., LoRa 2.4 GHz) in order to perform inter-satellite low-speed communication to FSO satellites. 2. The FSO satellites will aggregate the packages received by the RF ISM channel and will perform a rapid FSO download when in view of an FSO ground station. From the ground station, the packets will be routed to each satellite operator via the internet. By using the 2.4 GHz spectrum, the inter-satellite communication will impose very limited RF noise on terrestrial communication, since 2.4 GHz communication has a significant loss in the atmosphere. 3. The upload channel may stay \"as is\" (based on RF channels), as the upload communication is commonly (significantly) narrower than the download communication. The network may use application layer encryption in order to maintain the privacy of data. Naturally, such a framework will require changes in the International Telecommunication Union (ITU) licensing procedures (mainly allowing inter-satellite RF communication). Yet, it should be beneficial for both satellite and terrestrial operators. It should be noted that the presented framework cannot support real-time communication, as it may only work on clear-sky nighttime conditions. Yet, the ability to use hundreds of existing telescopes located globally, without any need for regulations, may lead to a new means of satellite communication, which is most suitable for remote sensing applications such as the Planet [21] use-case. For future work, we would like to generalize the FSO network to be able to handle real-time cases such as full duplex communication between two remote points on Earth. The concept can be implemented by allowing two close pico-satellites to intercommunicate using RF link, based on existing long-range (ISM) WiFi at 2.4, 5, or 60 GHz. Existing commercial drones allow a 10-20 km full-HD video link (in LOS conditions)--such a communication link can be used to connect two close satellites.