Global Navigation Satellite Systems Engineering, Policy, and Design
The Federal Communications Commission should really consider updating its motto. “Firm, fast, flexible, and fair” has a bit of an old-fashioned ring. As mottos go, it fails to keep up with the times.
By Alan Cameron
The European Space Agency (ESA) awarded two contracts to Thales Alenia Space concerning system evolution of the European Geostationary Navigation Overlay Service (EGNOS).
By Inside GNSS
Britain’s own satellite navigation system, envisioned to fill the country’s Galileo void created by Brexit, may never see the light of day. Government officials don’t want to spend tax revenues to meet projected increasing costs.
Prime Minister Boris Johnson had enthusiastically supported a proposal for a £5 billion (U.S. $ 6.1 billion) project, and indeed it would have presented a boon to British aerospace industry. But now that he is preoccupied with the coronavirus crisis, ministers in his Cabinet are moving to quash the program as unaffordable.
Britain’s space industry had been deemed a national priority and was playing a key role in Galileo before the UK was barred from the program by its Brexit move. Surrey Satellite Navigation Ltd (SSTL) manufactured the majority, the near totality, of payloads aboard Galileo satellites now aloft. But the European Union stated allowing a non-member state, which Britain now effectively is, to use its military-grade signal would endanger security. Doubtless there were economic considerations as well.
The move to build a very British satnav system had been stimulated by a report that the British economy could lose an £1 billion per day if GPS became unavailable for any reason. A 2018 study lasting 18 months and costing £92 million assessed the feasibility of a UK satellite system; it concluded that a £5 billion cost seemed realistic. In March 2020, the project was postponed for six months as concerns grew about total costs rising further.
Photo: SSTL’s Galileo payload team with Payload #22, delivered in 2016. Courtesy SSTL.
By Inside GNSS
The MEMS-based inertial measurement unit (IMU) represents the single biggest positioning and navigation advance of the last 20 years. That assertion is made during the first of three panels in the webinar “Inertial Technology for Robotics, UAVs and other Applications,” freely available on May 6. The 1.5 hour presentation examines how this breakthrough plays in the fields of autonomy, high dynamics and challenging environments, including on the frontiers of space.
Three experts takes a close-up look at contemporary and emerging inertial sensor technologies and applications, from the laboratory to the factory to the field. Register here to attend. The webinar is sponsored by Sensonor.
MEMS (micro-electromechanical sensors) make possible a miniaturization of size, weight, power requirements and cost never thought achievable before. When MEMS inertial navigation pairs with GPS for navigation, the key factor is the error budget of each sensor and how that plays into the accuracy of the solution. Attendees will learn how the new inertial sensors’ reduced error budgets translate into higher system performance.
The presentation begins with the current state of the inertial art, delivered by a recognized expert. The second speaker describes a high-accuracy tactical-grade inertial measurement unit (IMU) with increased accelerometer performance to support demanding guidance and navigation applications.
This knowledge is taken to the field to examine the IMU’s role in successful satellite launch missions during the third panel. The attitude determination and control system (ADCS) rises to the challenge of an extremely demanding environments and set of requirements. A satellite moving at a speed of 7,500 meters/second over ground requires precise maneuvering, stabilization and point in order to obtain imagery at 1-meter resolution.
Questions from the audience are actively encouraged and will be addressed by the three speakers in the final portion of the webinar.
Webinar speakers:
Ralph Hopkins is a Distinguished Member of the Technical Staff and Group Leader in the Positioning Navigation and Timing (PNT) Division at Draper, a leading research & development organization. He is responsible for the design and development of inertial instruments and sensors. Ralph has served as Technical Director of advanced inertial instrument development programs including strategic, navigation and tactical grade gyroscopes and accelerometers. He holds an ME in Engineering Mechanics from Columbia University, and an MS in Engineering Management from The Gordon Institute of Tufts University.
Reidar Holm is a Product Development Manager at Sensonor, a producer and developer of high-precision, light-weight gyros and IMUs. He works MEMS R&D and design, ASIC design, low-stress package design, system design, assembly and calibration, and high-volume production for automotive, MEMS pressure sensors, accelerometers, gyros and IMUs. He has a Degree in Electrical Engineering and Electronics from University of Manchester Institute for Science and Technology (UK) in 1982.
Ryan Robinson is the Lead Guidance, Navigation and Control Engineer at LeoStella, a small satellite design and manufacturing company, He is responsible for the design, development, test, and delivery of ADCS subsystems on LeoStella satellites. He received a Ph.D. in Aerospace Engineering from the University of Maryland, College Park. Technical areas of interest include attitude determination and control systems design, sensing and actuation, nonlinear dynamics, and autonomy.
Register here for the free webinar, “Inertial Technology for Robotics, UAVs and other Applications.” The webinar will also be available for subsequent download, for those registrants unable to attend at the appointed time.
By Inside GNSS
In its order allowing Ligado Networks to use satellite frequencies for on-the-ground wireless, the Federal Communications Commission set conditions on the firm’s operations, but only at the very tail end. Those conditions are there to help protect GPS receivers from interference — interference the FCC acknowledges as being quite possible.
By Dee Ann Divis
Though the FCC approved Ligado Networks’ request to use satellite frequencies to support terrestrial 5G, opposition to the move remains firm as everyone waits to see what kind of measures are included in the final decision to protect GPS from interference.
By Dee Ann Divis
The five members of the Federal Communications Commission voted unanimously to approve a request by Ligado Networks to use satellite frequencies neighboring those used by GPS to broadcast from ground antennas for 5G, the agency announced Monday morning.
By Dee Ann Divis
“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
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
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
