**4.2 Introduction to MOSA**

U.S. DOD recommends OSA design using MOSA principles for future military satellite system development with a goal to achieve a balance between business and technical objectives that make a business sense in terms of (i) increase competition and lower system acquisition cost, and (ii) lower sustainment cost over its life cycle. MOSA design approach requires to implement five MOSA principles, including two Business (B) and three Technical (T) principles [1, 2]. **Figure 8** captures these five B and T principles. Recently, U.S. Navy augmented MOSA principles with addition five Naval Open Architecture (NOA) principles, including two business and three technical principles as shown in **Figure 8** [3].

Subsections 2.1 and 2.2 provide current implementation of the Technical principle 1 (T1) for the modular design of satellite Bus and mission PL, respectively. The remaining Subsections 4.3 and 4.4 discuss the implementation of T2, T6, Business principle 3 (B3), and B4 using DOD guidance for addressing the challenges presented in Subsection 4.1.

## **4.3 DOD guidance**

MOSA mandated the space system technical requirements be based on the maximum extent practicable on open standards as indicated in Section 3.2 of the U. S. DOD Guidebook for Program Managers [1]. The book provides MOSA<sup>2</sup> guidelines and contract language for generating a Request for Proposal (RFP) [1]. At the minimum, the RFP shall incorporate the following MOSA tasks that can help to minimize the MOSA implementation risk in the design, build and test of new satellite systems:

<sup>2</sup> Note that the term Open System Architecture (OSA) has also been used interchangeably with MOSA by U.S. DOD.

*Future Satellite System Architectures and Practical Design Issues: An Overview DOI: http://dx.doi.org/10.5772/intechopen.92308*

	- Percentage %ð Þ Open Key Interfaces <sup>¼</sup> Number Open Key Interfaces Total Number Key interfaces
	- Number and location of private extensions on open interfaces;
	- Contractor use of company private extensions on open standard middleware;
	- Open Software Design Tool Kits/Component Design Tool Kits (OSDTK/ CDTK) will be provided with a minimum of Government Purpose Right (GPR); Minimal license fees may apply for COTS items;
	- Percentage of Chief Engineers, IPT Leads and program team members on architecture, software, logistics and Test & Evaluation trained in Open Systems Architecture and the MOSA tools;
	- Future Competition Strategy included in the OA Business plan within the OSMP;
	- MOSA (or OSA) requirements flowed down to sub-tier suppliers and recorded in IBM Rational® DOORS® requirements database or an MBSE digital model.
	- Design a system that consists of hierarchical collections of software, hardware, and firmware Configuration Items (CI's). Document in the MOSA Analysis Report its modularization choices for the system design and any tradeoffs performed in accordance with the OA verification plan.
	- Document any processes or applications necessary to support MOSA in the MOSA Analysis Report.

The above U.S. DOD's guidance encourages the satellite system designers to consider the above MOSA items in the design and build of the modular and open satellite Bus and mission payload for future space systems. The following section presents a proposal for assisting the satellite system designers to implement these MOSA items along with assessment tools provided by U.S. DOD.

## **4.4 MOSA implementation and assessment tools**

It is observed that the U.S. DOD, U.S. civilian agencies (e.g., NASA, NOAA, etc) and U.S. satellite manufacturers/suppliers (e.g., LM, Boeing, Northrop Grumman (NG), Raytheon, L3, etc) are investigating approaches for the modular and open design and build of satellite Busses and mission PL's using MOSA modular and open design principles. **Figure 9** proposes an approach to design and build of future modular and open satellite Busses and mission PLs, and allowing the satellite buyers to: (i) Buy the satellite Bus (see Path A of the figure) and mission PL (see Path B) from different satellite manufacturers/suppliers, (ii) Have an option to choose a third satellite vendor to integrate the satellite Bus and mission PL (see Path C).

The proposed MOSA implementation approach shown in **Figure 4** consists of six basic steps that are incorporated into three execution paths, namely, Path A, Path B and Path C:

	- Step I-A: Develop Modular satellite Bus Architecture (MoBA). The MoBA subsystem components are described in Sections 1 and 2 (see **Figure 3**).
	- Step II-A: Designate KOSS's and select open standards for all internal satellite Bus subsystem components. Open interface standards selection and designation of KOSS are discussed in Sections 3 and 4.

#### **Figure 9.**

*Proposed implementation approach for design and build of satellite Systems allowing buyers to acquire satellite bus and Mission PL independently.*

*Future Satellite System Architectures and Practical Design Issues: An Overview DOI: http://dx.doi.org/10.5772/intechopen.92308*

	- Step I-B: Develop Modular Mission PL Architecture (MoPA). The MoPA subsystem components are also described in Sections 1 and 2 (see Figure 4).
	- Step II-B: Designate KOSS's and select open standards for all internal Mission PL subsystem components. Open interface standards selection and designation of KOSS for mission PL are also discussed in Sections 3 and 4.
	- Step III-B: Design and build Open Modular Mission PL System (OMoPS). This step is achieved by identifying all potential KOSS's from the any mission PL's to satellite Bus, i.e., the selected KOSS's should be independent of mission types. The mission PL manufacturer is responsible for integrating all mission PL components and have the PL ready for sale.
	- Step IV: The system integrator works with satellite Bus and mission PL manufacturers to develop a satellite system interface specification specifying all "open" and "close" interfaces between the mission PL-andsatellite Bus. All open interfaces between the mission PL-and-satellite Bus shall be selected to meet the business and performance objectives approved by the buyer. The system integrator performs satellite Bus and mission PL integration using the approved interface specification.
	- Step V: System integrator performs system test and verification subject to buyer's approval.
	- Step VI: System integrator delivers the satellite system to the buyer.

DOD has also developed MOSA tools to assist MOSA implementation and assessment of military satellite Bus and mission PL "Openness". These tools can also be used for civilian and commercial applications. The DOD tools include MOSA Program Assessment and Rating Tool (PART), Open Architecture Assessment Tool (OAAT), and Key Open SubSystem (KOSS) Tool:

• MOSA PART<sup>3</sup> : It is being used by DOD as the standard MOSA program assessment and rating tool for DOD space system programs.

<sup>3</sup> PART can be found from: https://www.dau.mil/cop/mosa/Lists/Tools/DispForm.aspx? ID=2&Conte ntTypeId =0x01002BC08FCA204040449CF11CB472BEEE1800AA6D1BC9926604469A02D DB936F94D1F

