A new digital signal generator that can be reprogrammed on-orbit, enabling it to broadcast new signals
Digital signatures for detecting spoofing attacks
Steerable regional beams in multiple frequencies and signal codes
“Bounce-Back” capabilities for recovery from attack, solar and other disruptions
The NTS-3 marks the first time in 40 years the service has launched such a pioneering effort, following GPS.
The Department of Defense PNT Strategy calls for future military efforts and the results to be classified, making it unlikely that NTS-3 experiments will benefit the majority of PNT users in the civil sector.
Satellites NTS-1, 2 and 3. (Illustration: Lt. Jacob Lutz, AFRL Space Vehicles Directorate)
Just last month we celebrated the kickoff of the GPS III campaign, reporting on the launch of the first space vehicle of that generation in the closing days of 2018. A new era had begun, heralded by a rocket’s blazing path, bearing aloft a new “lighthouse in the sky serving all humankind.”
Turn around and — whoa! Where did all these other new PNT satellites come from?
We attempt to chronicle them all in this issue, though I’m not sure we haven’t still missed some.
For years we’ve been talking about the Iridium constellation, a low-Earth orbit telecommunication network that can also deliver timing services to improve accuracy, and signal acquisition in urban environments. Were it not for the fact that 10 more of its satellites just launched in January, bringing the total of its second-generation NEXT constellation to 75, this would practically qualify as old news.
But let’s move on to the real new news. NTS-3 is the new kid on the block most closely related to the GPS family. In fact, integrally a part of it. This third Navigation Technology Satellite will go even beyond GPS III — whose capabilities, mark you, are not yet online — to investigate new experimental antennas, flexible and secure signals, increased automation and use of commercial ground assets.
Learn about 72 nanosatellites of the Spire constellation piggybacking on Galileo signals to offer GNSS radio occultation products for the weather community. This may not be exactly direct-to-user PNT, but it’s a derivative.
Finally, absorb the latest on Hawkeye 360 formation-flying Pathfinders, designed to detect and geolocate radio frequency (RF) signals, and use the data in search-and-rescue as well as commercial maritime operations.
Don’t stop there! Read about Planet, the breadloaf satellites, current population 300 with more coming, beaming down 1.2 million high-resolution Earthly images per day, useful for agriculture, defense, mapping and GIS, and a few other industries.
If a group of satellites is a constellation, what do you call a group of constellations? If we are to follow astronomy’s lead, I’ve just learned that the proper technical term is an asterism. However, I think galaxy will be easier to handle.
Satellite NTS-3 above Earth. (Illustration: Lt. Jacob Lutz, AFRL Space Vehicles Directorate)
Harris Corporation has been selected as the prime contractor to build Navigation Technology Satellite-3, the next-generation experimental positioning, navigation and timing (PNT) spacecraft. The satellite, called NTS-3, is expected to launch in 2022, with one year of experimental operations.
The Air Force Research Laboratory and the Space and Missile Systems Center selected Harris on Dec. 20, 2018, and announced it on Jan. 17.
PNT Testbed
As a unique testbed in geosynchronous orbit, NTS-3 will integrate several advanced technologies to demonstrate resiliency and new concepts of operation to include experimental antennas, flexible and secure signals, increased automation, and use of commercial ground assets.
Technologies matured and knowledge gained from NTS-3 are expected to transition to future generations of GPS and augmentation layers for national PNT capabilities.
Satellite NTS-3 closeup. (Illustration: Lt. Jacob Lutz, AFRL Space Vehicles Directorate)
“The National Defense Strategy tells us we must evolve our nation’s Position, Navigation, and Timing capabilities to be more resilient,” said AFRL Space Vehicles Director Col. Eric Felt. “NTS-3 is all about resiliency, and I am incredibly excited about the resiliency experiments our SMC, AFRL, and Harris team will be able to conduct with NTS-3’s innovative and flexible hardware, software, and waveforms.”
Agile Waveform Platform
In support of NTS-3, Harris plans to develop the Agile Waveform Platform, a digital signal generator that can be reprogrammed on-orbit, enabling operators to quickly develop and deploy new signals to meet rapidly-evolving needs on the battlefield.
Additionally, Harris’ electronically steerable phase-array antenna will support simultaneous broadcast of multiple waveforms in both Earth-coverage and spot-beam configurations.
NTS-3 will use Northrop Grumman Innovation System’s ESPAStar bus, building on AFRL’s EAGLE spacecraft that launched in April 2018.
The NTS-3 Space Experiment
Navigation Technology Satellite – 3 (NTS-3) was selected as the Space Vehicle Directorate’s next major integrated space experiment in 2015, and it represents AFRL’s first PNT flight experiment to prototype a more resilient PNT multi-layer architecture in accordance with the Space Enterprise Vision (SEV) and the Space Warfighting Construct (SWC).
Satellites NTS-1, 2 and 3. (Illustration: Lt. Jacob Lutz, AFRL Space Vehicles Directorate)
NTS-3 builds on a heritage of Department of Defense (DoD) satellite navigation (SATNAV) success that began in the 1970s with the predecessors of the modern GPS constellation. NTS-1 was developed by the Naval Research Laboratory (NRL) and launched in 1974 with two rubidium-vapor frequency standards that advanced the timing and navigation precision demonstrated by the earlier TIMATION satellites.
NTS-2 launched in 1977 as the first NAVSTAR GPS Phase I satellite, and demonstrated cesium frequency standards and a worldwide network for data acquisition. There has been no major DoD SATNAV developmental program for experimentation since then, until NTS-3.
In 2017, AFRL restructured NTS-3 to emphasize mission objectives to demonstrate disaggregated, resilient PNT in a multi-layer space architecture, as outlined by the SEV and the SWC. NTS-3 will provide space qualification for core technologies such as on-orbit digital signal reprogrammability and solid-state amplifiers. In addition to new signals, onboard experiments include improvements to timing accuracy and integrity, including ensembling to improve long- and short-term stability. NTS-3 will demonstrate key tactics, techniques and procedures (TTPs) for multi-layer PNT through all three segments of the SATNAV system: space, control, and user.
Ground Control
Braxton Technologies was selected in June 2017 to handle NTS-3 SATNAV ground control, while demonstrating and maturing innovative and affordable ground-based command and control capabilities to ensure resilient PNT in contested and denied environments.
Braxton experts also will demonstrate satellite ground-control technologies to inform future GPS ground-control systems. They will use the Multi-Mission Space Operations Center (MMSOC) open architecture standard, as well as the Air Force Satellite Control Network (AFSCN) for primary direct and secure communications with the future NTS-3 space payload.
Satellite NTS-3 in space. (Illustration: Lt. Jacob Lutz, AFRL Space Vehicles Directorate)
Ground control segment (GCS) objectives include commanding of multiple antennas to form high-gain regional beams in conjunction with traditional Earth coverage beams, and processing the subsequent impact on phase center bias and pattern variation.
The GCS will also incorporate commercial antennas for TT&C and experiment with automation of common functions to reduce the level of manual control that GPS requires. GCS development will emphasize cyber security and compatibility with Enterprise Ground Services (EGS).
Collaborators Wanted
AFRL/RV is seeking collaboration from industry, government agencies, and universities in developing experimental concepts and participating in the flight experiment.
