Global Navigation Satellite Systems Engineering, Policy, and Design
We stand at an existential crossroads while someone else decides our future. I don’t mean the choice of direction, currently roiling the front pages, that pits the national health against the national economy. No, this one doesn’t get the attention it deserves, outside of the PNT and the telecom communities, though arguably it could have equally long-running and widespread, perhaps catastrophic effects.
By Alan Cameron
“Ligado’s planned usage will likely harm military capabilities, particularly for the U.S. Space Force, and have major impact on the national economy,” two ranking Senators and a Representative wrote. The timing could not be worse, they said to allow what “is fundamentally a bad deal for America’s national and economic security.”
By Dee Ann Divis
The U.S. Air Force 2nd Space Operations Squadron has put the last operational GPS IIA satellite, SVN 34, into disposal cycle for April 13 to 20. This is effectively end of life, or space hospice if you will, for a satellite that has outlived its 7.5 year design span by 19 years.
The rite of passage brings to a close a 26.5-year era in which the IIA generation carried the gold standard of positioning 20,200 km (12,550 miles) above the Earth, circling the globe twice a day.
Nineteen Block IIA satellites, slightly improved versions of the Block II series (the first full scale operational GPS satellites), were launched from November 26, 1990 until November 6, 1997. The satellites were built by Boeing, formerly Rockwell Corporation. They broadcast the L1 C/A signal for civil users and the L1/L2 P(Y) signals for military users.
SVN-34, the last of its generation, was removed from service October 9, 2019 but kept on as part of the constellation as a decommissioned, on-orbit spare until April 13.
In the disposal process, “We push the satellite vehicle to a higher, less congested, ‘disposal orbit’ to eliminate the probability of collision with other active satellites,” said Capt. Angela Tomasek, 2SOPS GPS mission engineering and analysis flight commander. “[Then,] the vehicle is put into a safe configuration by depleting the leftover fuel and battery life and shutting off the satellite vehicle transmitters so no one else can access the satellite in the future.”
“As we continue to manage the influx of GPS III and maintaining other vehicles in a residual status, we have to be cognizant of effective risk management,” Tomasek continued. “As SVN-34 continued to age, we had to manage its aging components and likelihood of having a critical malfunction. We are at a stage where we are confident in the robustness of the overall GPS constellation to remove the last remaining IIA vehicle.”
Once SVN-34 arrives in its final orbit, 2 SOPS will hand over full tracking responsibility to the 18th Space Control Squadron at Vandenberg AFB, California, where it will be treated and catalogued like every other space object, on April 20.
“This disposal marks the end of an era in GPS history,” said Lt. Col. Stephen Toth, 2nd SOPS commander. “There are senior leaders and long-time contractors [who] launched and operated the IIA satellites at the beginning of their careers [who] are now here to see it end. It is an opportunity to reflect on the legacy and heritage of 2 SOPS and GPS to see how far we have come.”
By Inside GNSS
Experts at the NATO Communications and Information (NCI) Agency have developed a software-based tool that can estimate the area where an interfering signal would degrade or deny GNSS signals, and assess the scale of the interfering signal and its potential impact on operations. Principally of interest are jamming or spoofing attacks on GPS or Galileo, of course.
The Radar Electromagnetic and Communication Coverage Tool (REACT), was sponsored by the NATO Navigation and Identification Programme of Work. It serves as a proof-of-concept of how analytical tools could support the execution of operations. The tool is also available to NATO Nations free of charge. For now, the software is only used for trial and experimentation.
To use the software, operators input information on the particular jammers – their locations and technical characteristics — and the software produces a map of the area where the interfering signals would degrade or deny GNSS receivers. This can be displayed on the NATO Core Geographical Information System (GIS) map.
The next phase of the project focuses on ensuring the software can work on NATO classified networks, which would make it more available to operational commands to test and ensure such support measures are properly integrated into NATO operations.
The software and its estimations were demonstrated to operators during exercise Trident Jupiter 2019, part 1, to collect their feedback. The exercise gathered 3,000 military and civilian personnel as participants, evaluators and observers. Thirty NATO member and partner nations participated in nine different exercise locations across Europe.
“Ten consecutive twelve-hour working days and a relentless, ever-increasing, battle-rhythm tempo came to an end as Exercise Trident Jupiter 2019-1 (TRJU19-1) reached completion on Thursday, Nov. 14, 2019,” the agency stated.
TRJU19 was the largest and most complex exercise planned and executed by the Alliance’s Joint Warfare Centre to date. TRJU19-2 took place in March 2020.
“NATO’s adversaries have the ability to degrade or deny GPS-enabled capabilities,” said Jean-Philippe Saulay, a NATO Navigation and Identification Officer. “NATO must take appropriate measures to ensure Allied forces can operate in a degraded or denied environment.”
“NATO must maintain superiority in the electromagnetic environment, including but not limited to, positioning, navigation and timing services,” said Dr Enrico Casini, Communications and Navigation Engineer at the NCI Agency. “Situational awareness of navigation systems in a contested electromagnetic environment contributes to that superiority. NATO is enhancing its knowledge of electronic warfare technology,” Dr Casini said. “The electromagnetic environment has become even more contested in recent years. One aspect of that is interference with GNSS systems.”
Photos courtesy NATO Communications and Information Agency.
By Inside GNSS
JNC 2020, the largest U.S. military Positioning, Navigation and Timing (PNT) and GPS conference, has been rescheduled for September 8–11, 2020 at the same two locations near Cincinnati, Ohio.
By Inside GNSS
GPS keeps a digital twin sequestered in El Segundo, California. Galileo has an Earth-bound space vehicle in Noordwijk, the Netherlands, straining at its bonds, yearning to break free and fly with its brethren. Both constellation “ghosts” exist in an eerie testing twilight, being made to replicate the movements and reactions of their free-flying families. Their sacrifices could lead to better, more robust satellites in future generations.
By Alan Cameron
The Space Force’s Space and Missile Systems Center (SMC) announced Tuesday it would reschedule the launch of the GPS III SV03 satellite “to minimize the potential of COVID-19 exposure to the launch crew and early-orbit operators.”
Originally scheduled for late April 2020 on a SpaceX Falcon 9 rocket, the launch is now projected to go up no earlier than June 30.
By Dee Ann Divis
Though the pandemic impacts federal workers and contractors across the country, the early-March testing of GPS backup technologies finished on time and the analysis is expected to be completed on schedule.
By Dee Ann Divis
The European Union’s eCall emergency response system automatically calls emergency services in the event of a serious road accident, transmitting location information from a GNSS receiver (GPS and/or Galileo) installed in the car to local emergency agencies.
By Inside GNSS
After years of delay, we see movement toward a back-up service for PNT and ensuring that critical infrastructure owners and operators take steps to limit vulnerabilities.
By Dee Ann Divis
The 2020 Space Symposium has been rescheduled for October 31—November 2 this year, to be held as usual at The Broadmoor in Colorado Springs. GPS in particular and GNSS in general always form an important part of the program. The annual assembly gathers leaders, innovators, and entrepreneurs from the civil, commercial, military, research, and international sectors of the world’s space community.
By Inside GNSS
A new series of disciplined oven controlled crystal oscillators (OCXOs) incorporates an internal GNSS receiver with a 1PPS output, compatible with an external GPS, GLONASS, BeiDou or Galileo source. The IQCM-112 series from IQD is housed in a 14-pin 60mm square package.
By Inside GNSS
Hundreds, thousands of tiny satellites no bigger than a breadbox orbit the Earth, gathering a staggering amount of data and relaying petabytes of communication. These nanosatellites, commonly called cubesats, serve a variety of research and, increasingly, commercial roles. They work for science, exploration, technology development, education, telecommunications and other operations.
They are built to a standard dimension of 10 cm x 10 cm x 10 cm, or small multiples thereof. Typical weight is less than 1.33 kg (3 lbs) per U, or Unit, which equals on 10 cm cube.
Among other launch opportunities, the National Aeronautics and Space Administration’s (NASA’s) CubeSat Launch initiative (CSLI) can give a ride up to small satellites as auxiliary payloads on planned rocket missions.
To meet performance requirements, commercial cubesats must often report from a precisely known location. Faulty positioning can produce inaccurate data that will adversely affect commercial operations on Earth. Cubesats typically carry a commercial GPS L1 receiver to determine their orbit, as altitude and orbit determination and control form key parameters.
Cubesats often fly in formation and wil then use a GPS/GNSS receiver to co-ordinate and synchronize among themselves. Finally, they use GNSS for onboard synchronization of operations and for precise timestamping of Earth observation data
Though small is size, cubesats can carry a large price tag, up to hundreds of thousands of dollars per project. Pre-launch testing for quality assurance is critical, particular of the satellites’ PNT capabilities. Earth-bound testing cannot replicate the conditions of low-Earth orbit, where the satellites will be moving at several kilometers per second, and need to maintain awareness of the also moving GNSS satellites above them in mid-Earth orbit. Thus the key role of GNSS simulation in this burgeoning industry.
The content of this article is largely drawn from a blog post by Talini Pinto Jayawardena, a space science technologist with Spirent Communications, and also a research manager at the University of Bath. To read her full blog, which contains a detailed description of key performance criteria to test with a simulator, visit here.
Extensive discussion of Doppler shift handling, precise orbit determination, antenna performance, time synchronization, special events, onboard interference handling, and the impact of environmental test (vibration and thermal vacuum) is presented.
By Inside GNSS
