## 1 Introduction  
A CubeSat is a standardized, modular nanosatellite class satellite with a basic dimension of a cubic decimeter [1]. Over the last decade, CubeSats have been used as a fundamental tool for academic institutions to conduct innovative in-orbit technology demonstration missions [1] (p. 59) within a limited budget and human resources. Recently, small space businesses started looking at the business potential in the area by engaging in the development of CubeSats' subsystems. The continuous innovation in small satellite technology has been the driving force behind an increase in the capability of these classes of satellites in recent years. These tremendous advancements are mainly due to the continual miniaturization of microprocessors [1, 2]. As a result, various missions are being executed on a single CubeSat platform, with increasing mission sophistication. For these reasons, subsystems are designed to have multi-functionality requirements within stringent mass and volume constraints. As a result of this increased capability, CubeSats' applications have gradually expanded from simple technology demonstration missions and remote sensing mission platforms to more advanced and sophisticated missions. Mega-constellations using distributed space systems (DSS) [1] and deep space exploration [3] are some examples of current possibilities. These mega-constellation missions require the deployment of a massive number of CubeSats for the intended aims. Constellations using the CubeSat platform guarantee more ground coverage, greater built-in redundancy, and shorter revisit times, available for the same price as conventional big satellites [4]. Table 1 lists commercial CubeSat constellations with more than two functional spacecraft in orbit as of July 2022. This shows the gradual increase in CubeSat constellation missions in different application areas. The stakeholders are predominantly private space companies with commercial purposes to provide space-based satellite solutions by utilizing state-of-the-art technologies in the field. These services aim to provide affordable space-based solutions, while maintaining a profit margin [1] (p. 15). The cost of mega-constellation development depends on several cost driver factors with different levels of effect on the total project cost. The supply chain is a crucial factor which should be managed strictly to avoid any delay in the schedule. However, efficiency during the design and development phase also plays a decisive part in determining the project time and cost. Inefficiency in the development process leads to unnecessary costs that lead to potential bankruptcy [5]. In addition, it causes unwanted workmanship errors. Incorporating the design for assembly and manufacturing (DFAM) principle during the conceptual design phase of the satellite development leads to an increased efficiency and/or productivity [6] (p. 19). By observing further down to the level of the structure of the subsystems in satellite development, improvement in efficiency can be attained by reducing the assembly steps and simplifying the effort required during the integration, assembly, and testing processes. This is done by modularizing and standardizing the design process, while keeping a certain level of flexibility [6] (p. 74-82). Therefore, it is vital to critically evaluate all design processes and identify inefficiency in the process as much as possible. Design modularity is an essential element in satellite development which significantly affects the level of effort in the project team and its effect on development costs can be quantified [7]. A modularized satellite bus has standardized and reconfigurable components [7]. The reduction in design effort allows for shorter development time and this in turn results in an improvement in productivity and efficiency, particularly for mass production applications [7].