The Navigation Technology Satellite-3 (NTS-3) program is making major strides in developing a new navigation spacecraft for in-space demonstration. The NTS-3 is scheduled to launch to geosynchronous orbit from Cape Canaveral in 2023.

This summer, Northrop Grumman Corp. delivered the ESPAStar-D spacecraft bus to L3Harris Technologies of Palm Bay, Florida.

“The transfer of the bus allows L3Harris to move forward building the NTS-3 spacecraft,” said 2nd Lt. Charles Schramka, the program’s deputy principal investigator. “L3Harris will perform tests and begin integrating the NTS-3 PNT payload onto the bus. Together the bus and payload will form the NTS-3 spacecraft.”

Following L3Harris’s work, the Air Force Research Laboratory (AFRL) will test the bus with the NTS-3 ground control and user equipment segments, and will perform its own integrated testing on the overall NTS-3 system architecture.

Northrop Grumman has successfully delivered an ESPAStar-D spacecraft bus to L3Harris in support of the NTS-3 mission. (Photo: U.S. Air Force)

NTS-3 in the Vanguard. In 2019, the U.S. Air Force designated NTS-3 as one of three Vanguard programs — priority initiatives to deliver new capabilities for national defense. The NTS-3 mission is to advance technologies to responsively mitigate interference to position, navigation and timing (PNT) capabilities, and increase system resiliency for GPS military, civil and commercial users.

“This is the first time an ESPAStar bus has been built and delivered as a commercially available commodity,” said Arlen Biersgreen, NTS-3 program manager. “NTS-3 is using a unique acquisition model for the ESPAStar line that fully exercises the commercial nature of Northrop Grumman’s product line, in order to provide the bus to another defense contractor for payload integration using standard interfaces.”

The ESPAStar-D bus, built in Northrop Grumman’s satellite manufacturing facility in Gilbert, Arizona, includes critical subsystems such as communications, power, attitude determination and control, in addition to configurable structures to mount payloads.

The bus will “provide affordable, rapid access to space,” according to Northrop Grumman. Its configuration, using an Evolved Expendable Launch Vehicle (EELV) Secondary Payload Adapter (ESPA), allows multiple separate experimental payloads to be stacked together on one launch vehicle. AFRL developed the ESPA ring to transport space experiments, allowing for lower cost and more frequent trips to space for government and industry users.

Besides the bus delivery, there are other advances in the program.

GNSSTA receiver. In June, AFRL took delivery of an experimental receiver — GNSS Test Architecture (GNSSTA). The receiver was developed by the AFRL unit the Sensors Directorate, located at Wright-Patterson Air Force Base in Ohio, and Mitre Corporation. GNSSTA is a reprogrammable software-defined signal receiver that will allow the Air Force to receive both legacy GPS and advanced signals generated by NTS-3.

AFRL will continue its integration efforts through 2022 to ensure all parts are working together for the fall of 2023 NTS-3 launch.

“With the delivery of the bus we are entering into the next phase of payload integration,” Biersgreen said. “These recent breakthroughs allow the program to continue to move forward and prepare for launch of the first U.S. integrated satellite navigation experiment in over 45 years.”

Artist’s concept for NTS-3 in geostationary orbit. (Artist’s concept: 2d Lt. Jacob Lutz, AFRL)