SDA Selects Northrop Grumman, Lockheed Martin To Aid In LEO Data Relay Constellation

By John Oncea, Editor

Low Earth Orbit is home to thousands of satellites that are used for communications, military reconnaissance, spying, and other imaging applications. Soon it also will be the domain of the Space Development Agency’s data relay constellation.

Low Earth Orbit (LEO) refers to a specific region of space around Earth that is relatively close in proximity to the planet’s surface. Space.com notes the generally accepted understanding is, “An orbit around the Earth with an altitude that lies toward the lower end of the range of possible orbits. This is around 1,200 miles (2,000 kilometers) or less.”

In simpler terms, LEO is the region of space where most artificial satellites and the International Space Station (ISS) are located. It is characterized by its relatively low altitude above the Earth's surface and its relatively high orbital velocity.

Satellites in LEO typically complete an orbit around the Earth in roughly 90 to 120 minutes, depending on their altitude. This rapid orbital period is a result of the gravitational forces from the Earth being stronger at lower altitudes, which causes satellites to move quickly to counteract the pull of gravity.

Because of its relative proximity to Earth, LEO is an attractive region for various space activities and missions, including:

• Satellite Communication: LEO is used for communication satellites, as the shorter distance allows for lower signal transmission delays compared to higher orbits.
• Earth Observation: Satellites in LEO can provide high-resolution imagery of the Earth's surface for applications like weather monitoring, environmental monitoring, and disaster response.
• Scientific Research: The International Space Station (ISS) orbits in LEO and serves as a platform for conducting scientific experiments in microgravity.
• Navigation: The Global Positioning System (GPS) and other navigation satellite systems operate from medium Earth orbit, which is a subset of LEO.
• Technology Testing: LEO provides a testing ground for new technologies and concepts for future space exploration missions.

LEO is also home to a significant amount of space debris, which consists of defunct satellites, spent rocket stages, and other fragments. Efforts are being made to address the issue of space debris to ensure the sustainability of LEO activities.

Setting Up A Data Relay Constellation In LEO

The Space Development Agency (SDA) is the Department of Defense’s constructive disruptor for space acquisition, delivering needed space-based capabilities to the joint warfighter to support terrestrial missions through development, fielding, and operation of the Proliferated Warfighter Space Architecture.

SDA has a distinctive approach to business that prioritizes efficiency and affordability through the use of commercial development to create a widespread and resilient architecture. By utilizing spiral development methods, SDA will be able to continuously improve its product and adapt to evolving threats. SDA's commitment is to deliver a minimum viable product every two years, always on schedule.

To that end, SDA awarded two prototype agreements with a total value of approximately $1.5 billion to build and operate the Tranche 2 Transport Layer (T2TL) – Beta variant prototype constellation, consisting of 72 satellites, which will form the foundation of Tranche 2 of the Proliferated Warfighter Space Architecture.

SDA has granted firm-fixed-priced OTA agreements to Northrop Grumman Space Systems and Lockheed Martin. These agreements will allow each company to construct and manage 36 T2TL-Beta prototype constellation satellites. The satellites will be positioned in three orbital planes, with 12 satellites in each plane.

The T2TL-Beta spacecrafts are designed to provide worldwide communication access and offer constant global encrypted connectivity. This technology is crucial for supporting missions such as beyond-line-of-sight targeting, missile warning, and tracking advanced missile threats.

“We are now solidly in the procurement phase for Tranche 2 of the PWSA to support a 2026 delivery,” said Derek Tournear, SDA director. “Tranche 2 brings global persistence for all our capabilities in Tranche 1 and adds advanced tactical data links and future proliferated missions. The Beta variant of the Tranche 2 Transport Layer vehicles are similar to Tranche 1 Transport Layer vehicles while also integrating advanced tactical communication technology demonstrated by the Tranche 1 Development and Experimentation System (T1DES).”

Northrop Grumman wrote in a press release, “The satellites will integrate with, and expand the PWSA mesh network, utilizing high-data-capacity optical crosslinks to deliver accessible, near-real-time communications to U.S. warfighters and defensive platforms operating around the globe. The design for this latest iteration, known as Tranche 2 Transport Layer Beta (T2TL Beta), builds on the 42 Tranche 1 Transport Layer (T1TL) and 14 Tranche 1 Tracking Layer (T1TRK) satellites that SDA previously announced it had awarded Northrop Grumman. The T2TL Beta space vehicles add new broadcast and tactical waveforms improving the capabilities of the overall PWSA.”

Lockheed Martin noted in its release, “The T2TL Beta variant satellites will work alongside the Tranche 1 and Tranche 2 networks, providing technology enhancements and increased integration to advance the warfighting capability. The satellites will be deployed in orbit over a series of launches starting in 2026 and will undergo a continuous checkout and commissioning process.”

Network Access Anywhere On The Globe

Northrop Grumman and Lockheed Martin “will be responsible for 36 satellites comprising what SDA calls the “Beta variant” of the Transport Layer’s Tranche 2, which when completed will allow the network to be accessed anywhere on the globe,” writes Breaking Defense. “The Beta satellites will carry optical intersatellite links for cross-satellite communications and a UHF Tactical Satellite Communications (TacSATCOM) downlink for tactical users.” Two additional variants planned for Tranche 2 – “Alpha” and “Gamma” – will have slightly different downlink configurations.

The Pentagon's Joint All Domain Command and Control (JADC2) plan aims to connect military sensors to ground, sea, air, cyberspace, and potentially space-based “shooters” and the Transport Layer satellites are a crucial component of this plan.