## 2 Methods and Materials
### Alfacrux Ground Segment  
#### 2.3.1 Ground Station Architecture  
The ground station information technology (IT) architecture is composed of physical and logical components, shown in Figure 6. The physical components aim to provide the computational power and make the internal and external interconnection with the Internet, namely:  
* Two desktop computers, with I5 CPU, 8 GB of RAM, and 500 GB SATA Hard Disk;
* One Dell server with Intel(R) Xeon(R) E-2224 CPU @ 3.40 GHz, 8 GB of RAM, and 1 TB SATA Hard Disk;
* One load balancer, which allows balancing the links to the Internet;
* CAT 6 A cabling, used to interconnect computers, servers, and load balancer;
* Scripts for automation;
* One uninterruptible power source (UPS), which allows system autonomy for about 35 min without power from the electrical grid. The logical components are formed by operating systems, firmware, software, applications, and virtual machines, as follows:  
* Computers or operating stations: its purpose is to operate and control the software-defined-radio and antenna rotors using an orbit propagator and Doppler shift calculator along with the mission control software (MCS). The VirtualBox was installed for extra functions such as virtual private network (VPN) and monitoring with Zab-bix. Some examples of monitored parameters are processing load, RAM memory consumption, and SWAP memory consumption, among others. * Server dedicated to the subsystems necessary for antenna control and Doppler correction. It aims to provide the necessary hardware resources for Rotcld, a Hamlib rotator control daemon, and MCS applications. * General-purpose scripts to automate internal operation tasks. The AlfaCrux team implemented an architecture for the ground station that allowed remote and secure operation. The computers were configured not to be a single point of failure, having replicated the virtual machines and applications, allowing them to be switched quickly, in a matter of minutes. To monitor the IT architecture and its componentsin order to identify possible points of attention, such as overloads, unavailability, and loss of performance, the Zabbix monitoring solution was implemented. The Zabbix is an open-source and free solution with several applications in different contexts including, for instance, the aerospace field. The basic resources of the server and computers are monitored, such as CPU, RAM, and SWAP memories, disk writing and reading latency, bandwidth consumption, status of processes and containers. For the administration and remote operation of the ground station, an open-source VPN solution, the OpenVPN, was implemented, embedded in the pfSense Linux distribution. The encryption used is based on public and private keys, with each user having their unique access key. pfSense integrated solutions with the OpenVPN and the key export package were chosen for their ease in generating and managing keys, being considered mature and a reliable security solution used by several companies in the world. In order to mitigate the impact of power outage in the operation, a UPS capable of supporting the entire environment was implemented, being able to maintain the operation with the AlfaCrux and data management system for 30 min when the main power fails. Another important point to be highlighted is the need to configure the power schemes of the computers and the server. Specifically, the following characteristics were activated in the basic input-output system: power on after power outage, scheduled power on, and wake on local area network (LAN). To increase efficiency and reliability in the operation tasks, some scripts were created, and additional configurations were set up on the server as well as the desktop computers. On the client side, a batch script was developed with an interactive menu for connectivity testing, activation, deactivation, restart, and collection of information from the rotors and the software-defined radio (SDR), as well as a bash script to control and manage containers.