How STL Works

PNT measurements from STL are intended to be used for a variety of applications:

• providing position and precision timing that is resilient to regional outages of Global Navigation Satellite Systems (GNSS)
• aiding GNSS acquisition
• augmenting GNSS measurements when not enough GNSS satellites are in view

The STL system allows a receiver to decode the signal and perform precise Doppler and range measurements at attenuation levels that penetrate into GNSS-challenged environments. The strength and fidelity of the signal are sufficient to allow it to pass through structures and other occlusions, providing coverage in deep indoor and urban canyon environments.

Security is also a key attribute of STL’s PNT capability. The Satelles service utilizes signal authentication techniques to enable a proof-of-location approach that allows STL to deliver a secure, trusted time and location capability that is effectively impervious to manipulation.

In settings where both GNSS and STL time and location fixes are possible, STL complements GNSS with additional PNT information. The key advantage of STL, however, is its ability to provide time and position fixes under conditions in which GNSS is not available. In this respect, GNSS and STL are complementary technologies, and receivers supporting both are ideal to deliver assured PNT.

Detection and Mitigation of GPS/GNSS Disruption and Manipulation

PNT solutions based on STL detect and mitigate GPS/GNSS signal disruption and manipulation. Resilience is achieved through the strength and security of the STL signal and the design of user equipment.

The STL signal is about 1,000 times (30 dB) stronger than GPS/GNSS and extremely difficult to disrupt. This means that when the much weaker signal from GPS/GNSS is affected by interference (or simply degraded due to environmental conditions), an STL-equipped receiver detects the loss of GPS/GNSS service and continues to deliver rock-solid PNT data by seamlessly transitioning to STL.

As with disruption, the exceptional strength of the STL signal compared to GPS/GNSS makes it significantly less susceptible to attack and therefore more reliable when facing threats from manipulation. A further protection is in how STL exploits the complex and overlapping beam patterns of the Iridium satellite signals and incorporates authentication techniques in ways that make it very difficult to manipulate.

User equipment that integrates STL capabilities is designed to detect manipulation by constantly comparing PNT data from GPS/GNSS and STL to determine when the values deviate beyond an acceptable tolerance threshold. If a GPS/GNSS signal is hijacked by an inauthentic signal delivering false and potentially dangerous PNT information, an STL-capable receiver will generate a user alarm and automatically switch to STL as the primary source of PNT data.

Organizations that depend on accurate and trustworthy PNT information for civil and commercial applications can count on STL to provide resilience by overcoming the threats posed by GPS/GNSS disruption and manipulation.