# Verification Approaches for Nano- and Micro-Satellites
###### Abstract  
The study of the performance of the multi  
from the early tests described in this work would have been more difficult, if not impossible, to gain if employing a traditional \"stage-gate\" approach, under which integration testing would take place only after each individual subsystem is verified.  
The issue of low reliability in nano- and micro-satellites is directly faced in the work by [PERSON] et al. [7], who push forward a reliability engineering approach based on Failure Mode, Effects, and Criticality Analysis (FMECA) to manage CubeSat reliability data and prioritize criticalities early in the design phase. Applying a risk analysis methodology during the design phase offers the opportunity to implement corrective actions at little to no cost. Their approach was applied during the design phase of a 6-Unit university CubeSat, allowing for identification of the major criticalities of the design.  
Five research papers in this Special Issue are devoted to verification strategies for some mission-critical subsystems, such as the Attitude Determination and Control Subsystem (ADCS), the Thermal Control Subsystem (TCS), and the Power System (PS). [PERSON] et al. [8] report the development of a framework for hardware and software-in-the-loop verification of MOVE-II (Munich Orbital Verification Experiment 2) CubeSat, with a strong focus on the ADCS, showing how we can enhance the reliability of CubeSats through system-level testing. [PERSON] et al. [9] present and experimentally verify an attitude control strategy based on magnetometer-only measurements for detumbling and pointing of nano-satellites, to be used as a backup solution in case of failure of the primary ADCS, and preventing mission loss. [PERSON] et al. [10] report the in-lab development of a dynamic testbed for nano-satellite attitude verification, placing focus on the thorough performance assessment of all the subsystems building up the facility. [PERSON], [PERSON], and [PERSON] [11] explore the viability, from a thermal point of view, of a composite material with ZnO nanoparticles to be employed in lieu of aluminum for the primary structure of a CubeSat, by performing finite element thermal analysis. After recognizing scalability as an effective approach towards rapid subsystems development times, while reducing the cost and failure rate, [PERSON] et al. [12] present a modular approach for the power generation within micro-satellites, called the Solar Module Integrated Converter (SMIC), using the Ten-Koh micro-satellite as a testbed to prove this concept.  
Miniaturized electric propulsion may dramatically increase the range of missions achievable with nano-satellites. However, relatively low readiness level and unease to perform thorough tests are slowing down the spread of electric propulsion solutions. The work of [PERSON] [13] provides a flexible test platform to assess the mutual interaction between the electric propulsion systems with the hosting CubeSat platform interactions in terms of power consumption, chemical contamination, and generated thermal and electromagnetic environments from mechanical, electrical, magnetic, and chemical perspectives.  
Beyond the space segment, the launch segment has also been considered by the contributors of this Special Issue. Indeed, nano and micro launch vehicles (NMLVs) may become a viable solution to make launch costs of nano- and micro-satellites more competitive. [PERSON] et al. [14] present an experimental investigation of an Ethernet-based communication system to be implemented onboard NMLVs for interconnecting with the hosted payloads, showing how their solution has performance comparable to the much more expensive alternative, the TTEthernet standard.  
Finally, valuable in-flight experiences are reported in works by [PERSON], [PERSON], and [PERSON] [15] and [PERSON] and [PERSON] [16], demonstrating the importance of ground simulation facilities aimed at subsystems performance verification and investigation of in-orbit anomalies, respectively.