Systems-of-Systems Taxonomy: Space and Airborne Systems Perspective

This chapter discusses the taxonomy of Systems-of-Systems (SOS) with a focus on space and airborne systems perspective. A discussion with a broad view of taxonomy with considerations for space and airborne systems classification, including SOS and Family-of-Systems (FOS), will be presented. The chapter defines taxonomic categories considering dimensions in the classification of space and airborne SOS based on their acquisition strategy, operational mode, and problem domain. Commercial and military acquisition strategies will be addressed along with their intentional operational modes and problem domains. The space and airborne systems discussed will be Satellite Communication (SATCOM) systems, sensing and imaging satellite systems and Positioning-Navigation-and-Timing (PNT) satellite, and military and commercial aircraft systems. The chapter provides examples on notional military SATCOM and manned aircraft systems.


Background and introduction
The term "Taxonomy" used in this chapter will be borrowed from the definitions presented in Refs. [1][2][3], but with an emphasis on space and airborne perspective. This chapter defines taxonomy as a hierarchical structure framework to classify space and airborne systems terms into parent-and-child relationships, where each level of a hierarchy can be referred to as a "Category." In this chapter, "Systems" will be categorized as Systems of Systems (SOS) and Family of Systems (FOS). For general military space systems, military space FOS can be categorized as (i) Satellite Communication (SATCOM) systems, (ii) Sensing and Imaging satellite systems, and (iii) Positioning-Navigation-and-Timing (PNT) satellites. Practically, civilian space FOS can be categorized as (i) commercial FOS of Broadcasting satellites, (ii) commercial FOS of Wideband Internet satellites, and (iii) commercial FOS of Data, Video, Audio Communications satellites. In general, commercial space FOS can be categorized as (i) NASA FOS of Near-Earth Missions, (ii) NASA FOS Deep Space missions, and (iii) NOAA FOS Earth Surveillance satellites. SOS can be a selected group of FOS that are connected together. For space systems, they (SOS) can be categorized as military, civilian and commercial space systems. For airborne systems, they can be categorized as military and commercial airborne systems, since civilian and commercial airborne systems are practically identical. In general, airborne systems can be categorized as (i) military manned aircraft systems, and (ii) military un-manned aircraft systems. Similarly, for commercial aircraft, it is also can be categorized as (i) commercial manned aircraft systems, and (ii) commercial un-manned aircraft systems. Figure 1 presents our view of taxonomy for "systems". This chapter will focus on SOS taxonomy for space and airborne systems. Due to the constraint on the length, this chapter will only provide two taxonomy examples on space and airborne systems, where a generic space and airborne systems' taxonomies will be presented. For airborne systems, the example will be focused on manned airborne systems. The chapter is organized as follows: i. Section 2 describes existing SOS taxonomy framework described in [3]; ii. Section 3 discusses our proposed SOS taxonomy framework for space systems; iii. Section 4 proposes an approach for SOS taxonomy framework for airborne systems; iv. Section 5 provides examples on notional military SATCOM and manned aircraft systems; v. Section 6 concludes the chapter with remarks on the taxonomy's needs for future space systems.

Figure 1.
A taxonomy definition of systems.

Description of existing SOS taxonomy framework
This section describes a current perspective on the SOS taxonomy framework, where SOS can be categorized as three types: • Acquisition type Each of the type will be classified into different component as shown in Figure 3.
The following provides a summary of the three types and their associated components.
• Acquisition type: SOS is classified based on how the systems acquired [3]: • Dedicated SOS: Is defined as planned SOS, where they are consciously designed and engineered from the beginning to be SOS, where the interaction between the component systems is expected when the systems are acquired. As pointed out in [3], in the past, many military SOS were not acquired in this manner, and the emerging trend is to design military systems around the SOS concept.
• Virtual SOS: Unlike dedicated SOS, this type of SOS is un-planned when the component systems are engineered and acquired. Another characteristic of these systems is that once their use has ended the • Operational type: SOS is classified based on how the systems operate [3]: • Chaotic SOS: This type of SOS has no central control authority or managerial entity and thus no agreed upon purpose.
• Collaborative SOS: For this type of SOS, the component systems interact voluntarily almost out of necessity. Control and management authority have little power to coerce the behavior of the component systems. Control and Management authorities may issue standard practices and procedures by which components must operate to be a part of the larger system, but ultimately it is up to the component systems to acquiesce to those standards to become part of the larger system (as with the Internet). The overall behavior of these systems may still be somewhat unpredictable.
• Directed SOS: This type of SOS is designed to have its control by a central management authority. The systems are designed and operated for a specific purpose.
• Domain type: SOS is classified based on how the domain that systems operate [3]: Current SOS taxonomy framework [3].
• Social SOS: Is defined as SOS that are either physical or conceptual SOS classes. As pointed out in [3], a social SOS is government.
• Conceptual SOS: These systems do not exist as tangible entities in physical space nor do they operate on or manipulate matter. Systems that are conceptual include those in which humans interact with concepts or those that require no human intervention at all.
• Physical SOS: These systems are operating in or on the physical world. These systems involve interactions between humans and the physical world or systems that are completely embedded in the physical world with no human interaction. These systems are composed of component systems that are tangible or affect matter. Figure 4 describes the proposed SOS taxonomy for space systems, where SOS can be categorized as military SOS, civilian SOS and commercial SOS. As discussed in Section 1, military SOS can be classified SATCOM SOS, Image/Sensor SOS, PNT SOS, and mixed SATCOM + Image/Sensor + PNT SOS. Similarly, the classifications for civilian and commercial SOS are also shown in Figure 4.

Proposed SOS taxonomy framework for space systems
Each type of the military SOS (e.g., SATCOM SOS) can be further classified in terms of acquisition type, operational type and domain type. Using the current framework described in the above section [3], this section derives the proposed taxonomy framework for space systems. The section is organized as follows: (i) Section 3.1 presents a taxonomy framework for military space systems, (ii) Section 3.2 addresses the commercial space systems, and (iii) Section 3.3 discusses the taxonomy framework for civilian spaces systems.  Figure 6 presents our proposed SOS taxonomy for commercial space systems. The SOS taxonomy framework for commercial space systems can be categorized as:

SOS taxonomy framework for commercial space systems
• Acquisition type Note that the commercial framework missed a component in the acquisition type, namely, virtual SOS. This is because the SOS solution is usually derived from customer's needs. While for military space systems, due to the threats dynamic, the warfighter needs are changing at a fast pace and there will be un-planned SOS components to be deployed.  Figure 6 presents our proposed SOS taxonomy for commercial space systems. The SOS taxonomy framework for civilian space systems can be categorized as:

SOS taxonomy framework for civilian space systems
Note the proposed SOS taxonomy framework for civilian space systems is identical to commercial space systems, see Figure 7. Similar to commercial space systems, the SOS acquisition for civilian space systems is depending on a planned mission's needs.

Proposed SOS taxonomy framework for airborne systems
Again, using the framework described in Section 2, this section derives the proposed taxonomy framework for airborne systems. The section is organized as follows: (i) Section 4.1 presents a taxonomy framework for military airborne systems, and (ii) Section 4.2 addresses the commercial space systems. Note that the taxonomy framework for civilian airborne systems is identical to commercial systems. • Conceptual SOS Similar to military space systems, due to the threats dynamic, the warfighter needs are changing at a fast pace and there will be un-planned SOS components to be deployed in airborne platforms. However, there is an addition component that is included in the domain type, namely, conceptual SOS. For airborne systems, this conceptual SOS component provide pilot training systems that have components existed in both physical and non-physical domains. For the physical domain, the pilot training system includes the training facility. For the non-physical domain, the pilot training system includes the cyber space component, where the pilots encounter the non-physical entities for training purposes.

SOS taxonomy framework for commercial airborne systems
The SOS taxonomy framework for commercial airborne systems is very similar to the military airborne systems, except that the SOS component for acquiring un-planned systems is no longer required. Thus, the framework includes:

Examples on notional military space and airborne systems
This section provides examples of taxonomy on notional military space and airborne systems since the case for civilian and commercial systems can also be derived directly from these examples. Figure 10 illustrates the two examples to be described in the following subsections. Subsection 5.1 presents an example of a taxonomy framework for a typical military SATCOM SOS. Subsection 5.2 provides an example of a taxonomy framework for a typical manned military aircraft that can be used for the derivation of a taxonomy framework for un-manned military aircraft.

A notional military SATCOM system
A typical military SATCOM system with a fully process SATCOM payload can be classified into the following subsystem components that are part of a SOS design [4]: The FDPS is the heart of a fully processing payload, and a typical FDPS includes the following components [4]: • Analog-to-Digital Converter/Digital-to-Analog Converter (ADC/DAC) • Digital Processor (e.g., Field Programmable Gate Array (FPGA)) Using a typical fully process SATCOM payload described above, Figure 11 provides a SOS taxonomy framework for a notional military SATCOM system operating in an SOS environment.

A notional military airborne system
A typical military manned airborne system can be classified into the following subsystem components that are part of a SOS design [5]:

Conclusion
This chapter provides descriptions of SOS taxonomy frameworks for space and airborne systems. A broad view of taxonomy frameworks with considerations for space and airborne SOS and FOS were presented. Using existing SOS taxonomy framework, the chapter proposed SOS taxonomy frameworks for space and airborne systems based on their acquisition types, operational modes, and problem domains. Examples on SOS taxonomy were provided for notional military SATCOM and manned aircraft systems. Similarly, examples for manned airborne and other space systems can also be derived by tailoring the framework presented in Section 5.

Conflict of interest
The preparation of this chapter was not funded by Gulfstream Corporation, and it was done by the author using his own time and resources, thus it does not represent Gulfstream's view on airborne system taxonomy.

Notes/Thanks/Other declarations
The author wishes to thank his wife, Annie Luu-Nguyen, for her immense patience and support.