The FAA mission is to promote airspace safety and the efficient use of the airspace. An important part of that mission is the maintenance, operation and sustainment of ground-based radars within the National Airspace System, or NAS. 

Ground-based radar systems continue to be required for air traffic surveillance for the FAA to:

• Detect aircraft not transmitting Automatic Dependent Surveillance-Broadcast, or ADS-B, due to improperly installed avionics, transponder failure, or non-equipped ADS-B aircraft
• Complement ADS-B surveillance coverage areas (in rule and non-rule airspace)
• Provide surveillance back-up service to ADS-B as needed for service resilience and safety
• Provide Air Traffic Control weather precipitation information until new solutions are deployed

The Terminal and En Route Surveillance Technical Refresh Portfolio, or TES TRP, validates, prioritizes, and manages projects necessary to sustain and maintain terminal and en route ground-based radar surveillance systems in the NAS.

The TES TRP is structured to provide streamlined acquisitions for sustainment of these systems by prioritizing and consolidating portfolio projects until the radars are divested or replaced. TES TRP is developing sustainment strategies and technical refresh projects addressing immediate technology and hardware obsolescence. Without an approved airport surveillance radar replacement program, these systems will be required to operate beyond 2040. The TES TRP is a strategic investment initiative to address the continued  sustainment needs of these systems until divested or replaced by the Radar Modernization Program.