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Communication Physical Medium

The physical medium selected for ground segment networking directly affects the mission's vulnerability to passive interception, traffic flow analysis, and electromagnetic eavesdropping, making medium selection a security design decision that must be informed by the mission's threat model. Fiber optic cabling transmits data optically and does not produce the same conducted or radiated electrical emanations as copper cabling, reducing exposure to proximity-based electromagnetic collection. Fiber may still be intercepted through physical access, optical coupling, compromised patch points, or endpoint equipment, and medium selection alone does not conceal traffic timing or volume from an observer with access to the link or its endpoints. Fiber should therefore be considered where the threat model identifies electromagnetic emanation or physical-medium interception risk, while cryptographic and physical protections remain applicable, particularly for links carrying mission-sensitive data such as command uplink traffic, cryptographic key material, or mission planning data. The selection of physical medium should be treated as a threat-informed engineering decision evaluated for each network segment based on the sensitivity of the data carried, the physical accessibility of the cabling, and the threat environment of the facility in which the cabling is installed.

Sources

ID: CM0071
Tier: III
Onboard SV CM 
Created: 2022/12/08
Last Modified: 2026/08/06

Pre-Operations Government

Acquisition requirements should address physical network medium selection as a security design criterion for ground system networking, requiring that the choice of medium for each network segment be documented as a threat-informed design decision that accounts for the sensitivity of data carried on that segment and the electromagnetic eavesdropping and traffic flow analysis threats applicable to the facility environment. Requirements should specify that network segments carrying mission-critical or sensitive data, including command links, cryptographic material distribution, and mission planning traffic, use fiber optic or equivalent non-radiating medium unless a security risk assessment documents an acceptable basis for using copper or wireless alternatives with compensating controls. Contract language should require that the physical medium selection for all ground system network segments be documented in the network security architecture deliverable and reviewed by government technical authorities, with any deviation from the preferred medium for sensitive segments justified against the threat model. Evaluation criteria should assess offerors' proposed network medium selections, the rigor of their threat model inputs to those decisions, and their experience designing secure ground segment networks for space missions with comparable data sensitivity requirements. Verification should confirm that the installed medium and cable routing match the approved design and that splices, patch panels, connectors, and termination points are limited to authorized locations, documented, physically protected, and inspected for unauthorized modification.

Pre-Operations Developer/Supplier

Physical medium selection must be incorporated into the ground system network design process as a security attribute evaluated alongside bandwidth, latency, and cost, with the threat model providing explicit inputs that identify which network segments and facility locations are exposed to electromagnetic eavesdropping or traffic flow analysis threats that would warrant fiber optic medium. Fiber routes and connection points for security-sensitive segments should be protected according to their physical exposure and data sensitivity. Routing through uncontrolled areas should be avoided or protected through an approved protected-distribution approach. Splices, patch points, and maintenance access must be controlled and documented. Optical-loss or intrusion monitoring may be used where the threat and operational benefit justify it, but it must not be assumed to detect every tapping method. For facilities where the threat model identifies proximity-based electromagnetic collection as a realistic adversary capability, the transition from copper to fiber should extend to all segments carrying sensitive data, not only the highest-classification links, as partial implementation leaves residual copper segments that an adversary can target. Where copper or wireless media are used, the design must apply protections appropriate to the identified interception and emanation risks. Sensitive data must retain its required cryptographic confidentiality and integrity protections, and the physical medium must receive the access control, shielding, or monitoring required by the threat assessment. Medium selection decisions and their security rationale should be documented as part of the ground system configuration baseline, enabling future security assessments to verify that the physical layer security posture remains consistent with the current threat environment.