U.S. DoD Sees Resilience in LEO Constellations

2021-06-30  |  4 min read 

The emergence of lower earth orbit (LEO) satellites has dominated the space and satellite industry in recent years. A seemingly ever-expanding number of these satellites is launching frequently, supporting applications ranging from fifth-generation (5G) non-terrestrial networks (NTN) to automotive and Internet of Things (IoT) applications. An article from Via Satellite recently confirmed that U.S. Defense Department agencies now strive to demonstrate the viability of LEO constellations for a variety of military applications.

A LEO approach was considered in years past for applications ranging from military communications to mission support. The benefits of numerous small satellites covering an orbit as a connected unit were clear. According to the article, however, any plans for LEO satellites were stifled by size, weight, and power (SWAP) constraints as well as cost projections. Recognizing recent technology advancements in the commercial sector, the U.S. Defense Department sees an opportunity to overcome those challenges to leverage LEO satellite network constellations.

Traditionally, the DoD focused on geostationary orbit (GEO) and other higher-orbit satellites – very complex systems with a longer development and production cycle. The ViaSat article notes, “The new birds will host sensors that comprise seven capability layers to seamlessly perform data communications, track hypersonic and cruise missiles, and provide enhanced battle management, navigation, ground support, and deterrence from space.”

From fall 2022 through spring 2023, 28 satellites are expected to launch. Currently, the DoD’s Space Development Agency is focused on the launch of four technology demonstration satellites. The ViaSat article notes that these demonstrations seek to prove how optical crosslinks will allow the data transport layer satellites to talk to each other as well as satellites in commercial networks. The program's goal is also to determine if the DoD can leverage commercial LEO constellations for military use. The roadmap for this program includes evolving capabilities and therefore rolling tranches every two or so years.

To prove the viability of this LEO program, success will depend on performance assurance throughout the mission. For modern satellites, this task is twofold: proving capabilities for military applications and verifying performance at higher frequencies and wider bandwidths. Due to spectrum crowding, LEOs are increasingly being deployed at higher frequencies, where more spectrum is available. For cellular NTN and other satellite-enabled communications, millimeter-wave technology offers the preferred spectrum for wideband and ultra-wideband communications.

Technological evolution always reveals new challenges. Designers must pinpoint potential problems, verifying performance before launch and throughout the mission to guarantee success. Wireless technologies increase signal bandwidth and use higher-order modulation schemes to achieve faster data rates. Wider bandwidth is a sought-after feature of millimeter-wave communications. However, wider bandwidth and higher-order modulation schemes introduce challenges related to link quality requirements at millimeter-wave frequencies. Wide bandwidths also introduce more noise as they enable high-throughput data, range resolution and accuracy, and low latency.

Download the new white paper, Prove Satellite Performance at Millimeter Wave Frequencies, for guidance on verifying and predicting real-world satellite performance and overcoming challenges at high frequencies and wide bandwidths. A LEO constellation represents a new approach for the Department of Defense, but the nature of military applications remains critical. Mission success will depend on performance assurance.