Photo: SpaceX

On April 27, 2024 the SpaceX Falcon 9 medium-lift launch vehicle launched into orbit Galileo satellites GM25 and FM27 from Kennedy Space Center in Florida. This was Falcon 9’s 20th and final launch.

The EU Agency for the Space Programme (EUSPA) confirmed in a statement that it is now in the Launch and Early Orbit Phase (LEOP) stage of the two new L12 Galileo satellites. They will join the current Galileo operational fleet in the upcoming months. The latest batch of Galileo satellites are being operated by EUSPA and the Galileo Service Operator for the Early Orbit Phase (EOP).

The EUSPA operations team, through its Galileo Service Operations provider, took over the satellite operations as the satellites were separated from the launch vehicle and their automated initialization sequence started. Telemetry has been successfully acquired, their solar panels deployed and the batteries are charging, bringing the satellites to what is called the Holding Point, according to EUSPA.

The EOP is a vital step in a space mission, running through the gradual activation and testing of platform satellite components, once in orbit. From the Galileo Control Centre in Oberpfaffenhofen, Germany, the dedicated LEOP team will navigate the satellites to their designated orbit within the coming days. Following rigorous in-orbit testing and commissioning, the satellites will integrate into Galileo’s operational constellation at 23,220 km.

The mission is a collaboration between the European Commission, which lead the management of Galileo; EUSPA, which manages operations and services with the support of the Galileo service operator (SpaceOpal); and the European Space Agency (ESA), which serves as the design authority, responsible for development.

<p>The post SpaceX successfully launches Galileo GNSS satellites first appeared on GPS World.</p>

Paul McBurney

The need arises from attacks directed by bad actors on a large scale, such as electronic warfare, and on a more humane scale, by bad actors such as self-jammers and spoofers. On top of that, normal interference can cause desensitization and denial of service on GNSS receivers from myriad terrestrial and satellite communications.

The PTA plan presents the Denial Radius Reduction Ratio (DRRR) figure of merit and shows that a J/S increase of 15 dB produces a DRRR of 0.18. Whereas a receiver without this additional 15 dB of J/S could be denied fixing out to 1 km from a given transmitter, a receiver with an additional 15 dB J/S would be denied out to only 180 m from the same transmitter.

The improvement in terms of area is proportional to radius squared. The article identifies that the J/S capability is different among GNSS signals and the best performance is obtained with L5, mainly because it has the highest chipping rate. L1C has a code length of 10,230 chips, the same as L5, but it is spread over 10 msec and has the same chipping rate as L1 C/A.

There are currently 72 L5 signals between GPS, Galileo, BeiDou and QZSS transmitting the same physical layer features of 10.23 MHz chipping rate, 1 kHz overlay codes and higher transmit power compared to nearly all L1 signals with a 1.023 MHz chipping rate and lower transmit power. The combination of these features at L5 is close to achieving this 15 dB performance level over L1.

Unlike current hybrid receivers, L5-first survives L1 jamming. (Photo: Carkhe / iStock / Getty Images Plus / Getty Images)

One might conclude that the current start of the art of a receiver with both frequencies (aka, a hybrid L1+L5) has this resilience. However, the market does not currently offer the ability to directly acquire L5 signals overall use cases of GNSS assistance without first acquiring signals at L1. This means they can only achieve this resilience when the interference is encountered after acquiring and fixing at L1. As soon as the L1 is lost and the position and time uncertainty grow beyond the receiver’s capacity to autonomously search for L5 signals, the receiver is denied service at the interference level tolerable at L1. If you cut the receiver into L1 and L5 pieces, only the L1 side is capable of fixing autonomously. As noted by Dennis Akos et al. (“Testing COTS GNSS Receivers Using Only a Subset of Supported Signals,” ION JNC 2023), “support for several signals/frequencies provides integrity and robustness.” Specifically, “under jamming scenarios, signal diversity can allow a receiver to still generate an accurate position solution.”

Current receivers are not able to acquire L5 for reasons related to history, cost and power consumption. Historically, the promise of L5 accuracy was so attractive that it was added to legacy chipsets based on L1 even when it was only partially deployed. It was impractical at that time to require L5 acquisition when there were fewer L5 satellites than at L1. Cost and power are related to the fact that L1 receivers’ acquisition methods are sized to acquire the L1, E1, B1 and G1 signals. Memory and compute capacities, including the digital clock speed, are sized for slower chipping rates and hence shorter code lengths. At this performance level, conventional time domain correlation is adequate. Some receivers deploy frequency domain methods at L1 and achieve a lower cost and power than time domain methods with similar capacity. However, the L5 acquisition complexity with time domain correlation is 100 times more than L1 as its complexity increases with N2, meaning the cost and power to acquire L5 is out of reach. While using a time domain acquisition engine to acquire L5 may be possible for strong signals when the code and frequency search space is constrained for those signals, directly acquiring L5 with conventional methods would have serious shortcomings in many use cases.

Interestingly, the signal designers across all GNSS systems have cleverly designed the L5 signals so they can be easily acquired after acquiring their counterparts on L1. The L5 primary and secondary code is predictable based on learning the L1 primary code and navigation data bit phase. E5a and B2a primary and secondary codes can be predicted by learning the well-designed E1/B1 primary and secondary code phases that have the same total period: the combination of the 4 msec code lengths synchronous with 25 bits of secondary code are in phase with the E5a 100 msec overlay code. After an L1 fix with fine time, L5 can similarly be directly acquired easily with limited searching.

<p>The post L5-first for improved resilience in mass market GNSS first appeared on GPS World.</p>

Image: EUSPA

The European Union Agency for the Space Program (EUSPA) has published a technical document detailing the main characteristics of the new Galileo Emergency Warning Satellite Service (EWSS).

According to the document, Galileo satellites will transmit emergency warning messages directly to Galileo-enabled smartphones and other navigation devices. The satellites will offer information related to the hazard, such as type, severity, expected onset and duration, as well as the location of the affected area and instructions to follow. The alert content will be generated by national authorities and transmitted to Galileo for broadcast.

“With this new document, some of our key stakeholders can already start to work with this new service,” said Fiametta Diani, head of market, downstream and innovation at EUSPA. “Civil protection authorities in the member states can start to prepare for how they will manage the alert messages they will send via Galileo. The same goes for the receiver and chipset communities, who will have to process this message.”

In 2023, EUSPA began testing the EWSS in different locations in Europe. “We have run trials in Toulouse and in Germany, specifically with a simulated explosion,” Diani said, “like what you might see with an industrial accident. We have also tested a tsunami alert in Cyprus.” The Union is developing the tsunami application together with Japanese partners. EUSPA has also finished flood testing in Belgium and Luxembourg.

EUSPA plans to launch the new EWSS in 2025, Diani said. “As for the receivers, we are working to get our chipset and receiver industry ready,” she said, adding that this process is also supported by the Fundamental Elements program.

Fundamental Elements is an EU funding mechanism that supports the research and development of European GNSS-enabled chipsets, receivers and antennas. The projects are part of the overall strategy for European GNSS market uptake, said EUSPA.

The member states and the correlating national civil protection authorities will initiate warnings, according to Ignacio Alcantarilla Medina of the European Commission.

“[Authorities] will send a message to the Galileo system, and then Galileo will transmit that message through its satellite signals to the users,” he said.

According to EUSPA, the service is designed to be used worldwide to serve as a backup to the already existing mobile network warning systems.

<p>The post EU to launch Galileo-based emergency alert system first appeared on GPS World.</p>

Figure 1: Bobcat-1, with communications antenna stowed (left) and deployed (right). Bobcat-1 measures approximately 10 x 10 x 30 centimeters. (All figures except FIGURE 3 provided by the authors)

Bobcat-1 was a three-unit CubeSat developed and built at Ohio University’s Avionics Engineering Center in Athens, Ohio, and was named after the university’s mascot. FIGURE 1 shows Bobcat-1 with and without its antenna deployed. The satellite was launched to the International Space Station in October 2020 (see FIGURE 2) and deployed into low-Earth orbit (LEO) the following month (see FIGURE 3). In April 2022, it deorbited and burned up in Earth’s atmosphere as planned, after a successful 17-month mission, lasting eight months longer than anticipated. The last signal decoded from Bobcat-1 was received only about 10 minutes before the satellite’s demise, from an altitude of about 109 kilometers, by an amateur radio operator (ZR6AIC) near Johannesburg, South Africa, associated with SatNOGS, a global network of amateur satellite-networked open ground stations.

The main mission of the Bobcat-1 CubeSat was to evaluate the feasibility of GNSS-to-GNSS time offset monitoring from LEO. One of the secondary mission objectives was GNSS spectrum monitoring.

In addition, Bobcat-1 also included a side-mission, hosting a software-defined GPS/Galileo receiver developed by the University of Padova and Qascom — an Italian engineering company providing security solutions in satellite navigation and space cybersecurity — to perform its in-space demonstration and testing. This receiver served as a prototype for the receiver soon to be launched on NASA’s Lunar GNSS Receiver Experiment (LuGRE) mission.

Communications and control of the satellite utilized the 70-centimeter amateur radio satellite band (435-438 MHz) at a typical data rate of 60 kilobits per second and were primarily conducted using a dedicated ground station on the roof of the engineering building at Ohio University (see FIGURE 4). In total, Bobcat-1 collected and downlinked more than 656 megabytes of data during its lifetime. Over the course of the mission, Bobcat-1’s firmware was updated in-orbit on six occasions, allowing for minor enhancements to the data collection system.

Figure 2: Bobcat-1 launches aboard the Cygnus NG-14 resupply mission to the International Space Station. (All figures except FIGURE 3 provided by the authors.)

BACKGROUNDS: GNSS-TO-GNSS TIME OFFSET

GNSS-to-GNSS time offsets — also referred to as GNSS inter-constellation time offsets, inter-system biases or XYTOs — are among the critical parameters for full GNSS interoperability. Users with poor GNSS visibility, such as high-altitude spacecraft, which operate above the GNSS constellations, often do not have enough satellites in view to enable an accurate solution and can experience high dilution of precision. These users could benefit from XYTO estimates provided externally, assuming their receiver-characteristic inter-system biases (ISBs) are calibrated.

To determine a user solution using measurements from a single GNSS constellation, one must solve for four unknown parameters: the user’s spatial coordinates and the receiver-to-system time offset. This means that a minimum of four satellites must be visible to solve for a user solution. If a user has sufficient visibility of satellites from different constellations, a multi-GNSS solution can be determined. However, when applying measurements from multiple constellations, an additional unknown is added for each constellation used. For example, for a user solution incorporating measurements from both GPS and Galileo, one needs to solve for five unknowns: the user’s spatial coordinates, the receiver-to-GPS time offset, and the receiver-to-Galileo time offset. Since each constellation’s time scale is independent of the others, the inter-system time offset between the time scales leads to a prominent bias in a multi-constellation solution. Inter-system time offsets between GPS, Galileo, GLONASS, and BeiDou are generally expected to range from 10 to 100 nanoseconds, resulting in 3 to 30 meters of possible positioning error.

System-to-system time offsets are currently estimated by extensive networks of ground stations, such as those used by the International GNSS Service Multi-GNSS Experiment (MGEX). In addition, GNSS service providers often broadcast XYTO estimates in their navigation messages.

Figure 3: Bobcat-1 is deployed into low-Earth orbit by the Nanoracks CubeSat Deployer alongside SPOC, a CubeSat developed by the University of Georgia. (Photo: NASA)

So, why would estimating XYTOs from LEO be of interest?

Low-Earth orbit enables high GNSS visibility. The approximately 90-minute orbital period allows for observations from nearly all GNSS satellites multiple times per day. This enables high visibility of multiple satellites from each constellation, in turn enabling high observability of constellation parameters such as XYTOs, leveraging satellite-characteristics errors. In addition, tropospheric errors are absent and multipath is limited and can be bounded based on the CubeSat’s dimensions and geometry. Exploiting measurements from LEO could provide additional measurements and independent monitoring of the XYTO estimates provided by ground networks.

However, to estimate system-characteristic XYTOs, the receiver-characteristic biases need to be calibrated. The target is to reach accuracy of approximately 1 nanosecond or possibly lower. Therefore, the error sources need to be evaluated, mitigated, or bounded.

Figure 4: Bobcat-1’s dedicated ground station on the roof of Stocker Center in Athens, Ohio. (All figures except FIGURE 3 provided by the authors.)

Although the ionospheric effects are lower in LEO than on Earth, they cannot be neglected. Therefore, dual-frequency ionospheric delay estimates must be applied. To do so, the receiver’s inter-frequency biases (IFBs), which can introduce errors on the order of nanoseconds, need to be calibrated, as well as the satellite differential code biases (DCBs), orbit and clock errors and receiver antenna group delay. An additional challenge introduced by the LEO environment is the wide range of temperatures to which the receiver is subjected. Over a single orbit, the receiver’s temperature can vary from approximately 0 to 50 degrees Celsius. The effects of these temperature variations cause fluctuations in the receiver’s IFBs, which need to be evaluated and calibrated. Pre-launch measurements in a controlled environment using a climate chamber and two receivers of the same make and model were used for calibration. We have detailed those measurements elsewhere.

The multipath error can be bounded, as a first approximation, to 10 centimeters (or about 0.3 nanoseconds in equivalent signal delay) due to the dimensions of the CubeSat. However, given the mount of the antenna is on one of the CubeSat’s two 10 × 10 centimeter faces, that upper bound is in practice much smaller and the multipath error is mostly negligible.

Finally, the last remaining major error sources to be calibrated are the receiver ISBs. The main goal, to demonstrate the feasibility of LEO-CubeSat-based monitoring of GNSS XYTOs, requires showing the stability (or the repeatability) of the receiver biases in orbit.

Table 1: Summary of data collections discussed in this article.

DATA COLLECTION

Bobcat-1’s primary payload was a NovAtel OEM719, a triple-frequency multi-GNSS receiver, enabling measurements on all frequencies from GPS, GLONASS, Galileo and BeiDou, as well as the regional navigation satellite systems (RNSSs) QZSS and NavIC. The measurements were collected and downloaded, for post-processing purposes.

Pseudorange and carrier-phase measurements, as well as carrier-to-noise-density ratio estimates, were collected, together with the receiver’s position and velocity estimates, and other parameters such as the temperature measured by the two sensors embedded in the receiver. In limited instances, power spectral density measurements and in-phase and quadrature (I/Q) component samples were collected to support the secondary mission, GNSS spectrum monitoring. The limited downlink capacity of the satellite constrained these measurements to short time intervals.

Figure 5: Number of observations recorded by Bobcat-1 from each GNSS constellation during a data collection started on February 27, 2022.

The goal of the mission is to estimate the XYTOs for all the GNSS constellations. However, in this article only the Galileo-to-GPS time offset (GGTO) is considered. The Galileo Performance Reports published by the European Union Agency for the Space Programme (EUSPA) provide information on the accuracy of the GGTO broadcast parameters, which are typically within approximately 3 nanoseconds of the true GGTO. Therefore, the broadcast GGTO provides a point of comparison and reference for Bobcat-1’s estimates.

A summary of the data collections considered in this work is provided in TABLE 1. These data collections are among the longest recorded by Bobcat-1. As an example, FIGURE 5 shows Bobcat-1’s data collection for February 27, 2022. It should be noticed that data collections were initiated from the control station at Ohio University when the CubeSat was in view, and each data collection would start only when the satellite’s battery voltage was above a defined threshold. The collection would stop safely if a minimum voltage threshold was reached. The data sets collected during the first months of the mission had durations limited to one to four hours, since the minimum battery voltage threshold was set conservatively. However, as the mission continued, data collections recorded in the last several months before deorbiting were configured with lower thresholds, enabling continuous data collections with durations of up to 24 hours. During the longer data collections, the sampling period was set to 20 seconds to reduce the total quantity of data stored and downlinked. The work described here focuses on a select few data collections that span a period of five months between September 28, 2021, and February 27, 2022.

Figure 6: Bobcat-1’s ground track during a data collection for XYTOs estimation held in February 2022, approximately 24-hours long. Note that the blue dots correspond to the positions (latitude and longitude) of Bobcat-1. The red stars indicate that even if the position was calculated thanks to a multi-frequency and multi-GNSS solution, GPS L1 C/A measurements were not available. Analysis of the carrier-to-noise-density ratio measurements and comparison with the available spectrum measurements showed that in correspondence to those positions interference was present.

The data contain multi-frequency measurements from all systems, with an average of 180 observations made per sample. The maximum number of observations at once was 217. While multi-frequency measurements were collected from all constellations, this analysis only uses single-frequency measurements from two constellations: GPS L1 C/A and Galileo E1C.

RESULTS

There are two simple approaches to calculating inter-constellation time offsets: one involves computing multiple single-constellation user solutions, and the other involves a single multi-constellation user solution. Each approach has slightly different effects in terms of error propagation. In the first approach, the XYTOs can be calculated by taking the difference of the independently calculated receiver-to-system time offsets. This method requires at least four satellites from each constellation to be visible. In the second approach, all the receiver-to-system time offsets for all constellations involved in the solution are solved simultaneously. This reduces the number of measurements required per-constellation, with the minimum number of measurements needed being equal to the number of unknown state variables.

Figure 7: Broadcast GGTO (red) compared to Bobcat-1 Galileo-GPS time offset estimate, before calibration (blue) and filtered estimate (black). The results are related to data collection 181, started on December 27, 2021, which lasted about 16 hours (more than 10 orbits). The estimates’ variations, on the order of ±5 nanoseconds, are mainly due to temperature effects during the orbit and here are simply represented with a moving average.

In general, the latter method improves the XYTOs’ solution availability since the receiver-to-system time offsets for each system can be calculated with even fewer than four measurements from each system. For each sample point, the user solution was determined using this method, and the GGTO estimate was calculated by taking the difference of the receiver-to-GPS time offset and the receiver-to-Galileo time offset. This method allows the XYTO to be estimated by the receiver even when visibility is degraded. For example, as shown in FIGURE 6, Bobcat-1’s data collections are affected by interference, mostly on GPS L1, in some regions. Points where interference was believed to be present are marked by red stars on Bobcat-1’s ground track shown in the figure, specifically denoting points where the number of tracked GPS L1 C/A signals drops below four. For each sample point, the user solution was determined using the method discussed above, and the GGTO estimate was calculated by taking the difference of the receiver-to-GPS time offset and the receiver-to-Galileo time offset.

Figure 8: Difference between Bobcat-1 estimate and GGTO. The residual is mainly an estimate of the receiver inter-system bias that even pre-calibration shows to be stable in orbit as shown in Table 2.

FIGURE 7 shows (in blue) the GGTO estimate using Bobcat-1 measurements (data collection 181, started on December 27, 2021, and lasted about 10 orbits). The plotted values are the estimate of the system-to-system bias (GGTO) from which the receiver-specific ISB (Galileo-to-GPS) has not yet been removed. The oscillations visible in the unfiltered GGTO estimates are the result of temperature effects on the receiver. They can be mitigated by applying the calibrations made during pre-launch climate chamber testing, though for this analysis the estimates are simply filtered using a moving average (shown in black in the figure). Note that the abrupt change in the broadcast GGTO about 21 hours after the collection start corresponds to the start of a new day in UTC time, when a new estimate of the broadcast GGTO parameters was provided.

In FIGURE 8, the difference between the Bobcat-1 estimate of the GGTO and the broadcast GGTO is plotted (raw, in blue, and filtered with a moving average, in black). This is an estimate of the Bobcat-1 receiver’s Galileo-to-GPS ISB, which needs to be stable and repeatable in orbit, to enable accurate estimates of the true GGTO. As Figure 8 indicates, the receiver ISB shows stability even before calibration, showing periodical variations mainly due to temperature changes over the orbit.

TABLE 2 summarizes some results over a five-month period. Only the longest data collections were considered, but the shorter ones are also under analysis to provide a longer and denser observation window. From the data in Table 2, the Bobcat-1 receiver’s mean Galileo-to-GPS ISB, estimated by comparison with the broadcast GGTO, shows a standard deviation, pre-calibration, of less than 1.5 nanoseconds over five months. Considering that the accuracy on the broadcast GGTO is expected to be ≤ 3 nanoseconds, this estimate of the receiver ISB shows that its stability over time may enable accurate XYTO monitoring from LEO.

Table 2: Bobcat-1 Galileo-to-GPS time offset vs broadcast GGTO, for different data collections over about five months. All figures in columns two through five are in nanoseconds.

The implementation of the receiver bias calibration, including the temperature effects, will refine this result. The final test will include assessing the performance of the calculated system XYTO, utilizing it in the solution of another receiver previously calibrated and at a known location.

CONCLUSIONS

Results of five 15+ hour data collections spanning a period of five months are compared. The difference between the broadcast GGTO and the GGTO estimate calculated using data from Bobcat-1 appears to be stable within 1.5 nanoseconds. Observing the in-orbit data and comparing it with the data collected previously in a controlled environment in the laboratory, a high correlation is observed between the bias change over time and the measured receiver temperature. The mitigation of this effect will enable stability of our receiver characteristic GGTO estimate to within 1 nanosecond. These experimental results suggest that a few multi-GNSS receivers in LEO could provide a method to monitor XYTOs in near real time, providing redundancy and diversity to the ground-network-based estimation system.

ACKNOWLEDGMENTS

The authors would like to acknowledge NASA’s Satellite Communication and Navigation Office (SCaN), NASA’s Glenn Research Center, NASA’s CubeSat Launch Initiative (CSLI), and Ohio University for funding the Bobcat-1 CubeSat mission. Additionally, we thank Kevin Croissant and Gregory Dahart, previous student members of the Bobcat-1 team, and Dr. Frank van Graas, Ohio University Professor Emeritus and former faculty member of the Bobcat-1 team.

This article is based on the paper “Receiver-specific GNSS Inter-system Bias in Low-Earth Orbit” presented at ION ITM 2023, the 2023 International Technical Meeting of the Institute of Navigation, Long Beach, California, January 23-26, 2023.

<p>The post GNSS timing measurements from a low-Earth orbiting satellite first appeared on GPS World.</p>

Photo: ESA

Qualinx, a company specializing in ultra-low power wireless tracking and connectivity semiconductors, has announced a partnership with the European Union Agency for the Space Programme (EUSPA). This collaboration, under the Fundamental Elements EU R&D funding mechanism, aims to develop a consumer-grade, low-power GNSS receiver for EUSPA’s GNSS authentication service.

The project focuses on the Galileo Open Service Navigation Message Authentication (OSNMA) service, which is designed to verify that users are receiving data from Galileo satellites. This service was introduced in response to an increasing number of spoofing incidents. Qualinx was selected for this project following a six-month selection process conducted by EUSPA.

Qualinx’s technology, known as digital radio frequency (DRF), transforms most analog functions of a wireless chip into digital circuits, which can be customized for each application through software. This technology is designed to reduce power consumption compared to traditional GNSS receivers. The company aims to provide smaller, more cost-effective solutions while extending the operating life of battery-powered navigation devices.

<p>The post Qualinx, EUSPA partner for GNSS receiver development first appeared on GPS World.</p>

Image: GMV

GMV and Astroscale UK are collaborating on a new project under the European Space Agency (ESA) collision risk and automated mitigation (CREAM) program. The project aims to transform satellite collision avoidance by using Galileo Signal-in-Space (SiS) capabilities.

As low-Earth orbits (LEO) become increasingly congested, satellite operators face difficulties efficiently carrying out collision avoidance maneuvers. In response, the ESA launched the project to explore alternative paths for late collision avoidance maneuvers. The collaboration uses the Galileo Return Link Service to improve the way satellites respond to collision risks.

Traditionally, communication with satellites for collision avoidance maneuvers has been constrained by the limited availability of ground station access. This limitation forces satellite operators to delay crucial avoidance maneuvers while relying on the final passes of ground stations.

GMV’s solution offers an alternative pathway for late maneuver commanding, designed to reduce the wait time for initiating collision avoidance. The initiative proposes a continuous and reliable communication path by using the Galileo, SiS and its Return Link Service. This approach allows for the seamless relay of collision avoidance maneuver decisions to satellites equipped with onboard Galileo-compatible GNSS receivers.

The Galileo system in this role also opens the door to potential synergy with other space situational awareness (SSA) services, such as the European Space Surveillance and Tracking (EU SST). According to GMV, this strategic collaboration could potentially set the foundation for a globally available collision avoidance service.

<p>The post GMV, Astroscale partner with ESA for Galileo SiS satellite collision avoidance first appeared on GPS World.</p>

I/NAV improvements for all Galileo Open Service users is a part of the new Galileo services portfolio. (Image: EUSPA)

In 2023, Galileo continues to provide the world’s most precise satellite navigation information, to more than four billion users worldwide. Galileo services have expanded with many new capabilities that are unique with respect to other GNSS.

EUSPA and ESA continue to enjoy an effective collaboration on the many development, deployment and evolution activities of the Galileo Program, each according to its responsibilities for service provision and system development with the European Commission acting as the program manager.

Stable service performance

The service delivery operations, and the maintenance of the operational systems, are managed by EUSPA, who supervises several contracts that carry-out the day-to-day activities from dedicated control and monitoring centers throughout Europe. The Galileo timing, navigation and SAR/Galileo services provided in 2023 have been delivered with excellent performances that continue to exceed the formal declarations for minimum performance levels (MPL), both in terms of absolute accuracy and overall service availability.

Expansion of service portfolio

Galileo FOC batch three satellites in storage at OHB Systems. (Image: ESA)

The service provision teams have been able to focus on improvements to, and expansion of, the Galileo service portfolio.

OS and I/NAV improvement

Galileo Open Service (OS) users can already benefit from an improved navigation message, being broadcast by the Galileo constellation since mid-2023, which considerably boosts their performance in terms of robustness and time to first fix.

An update of the Galileo OS service definition document (SDD) is planned for the end of this year. This fourth issue of the OS SDD will bring to the users new MPLs (e.g., ranging rate accuracy and ranging accuracy at high percentiles) and improvements of existing MPLs, such as the timeliness of certain notice advisories to Galileo users. This updated OS SDD will also introduce the OS extended operation mode, which is characterized by a gradually degrading ranging accuracy with respect to the nominal operational mode, including outages of the Galileo ground segment, thus increasing the robustness of the OS.

High Accuracy Service

As of the HAS initial service declaration on January 24, Galileo became the first GNSS constellation ever to enable a decimetre-level accuracy, free of charge on a 24/7 basis over most parts of the globe in nominal conditions. The HAS corrections are transmitted directly via the Galileo signal in space (E6-B) and through the internet with the corresponding performance levels systematically met since the declaration. All documentation available here.

OS-NMA

The OS Navigation Message Authentication (OSNMA) will be a free and open access service allowing the users to confirm that received Galileo navigation data has not been modified and originates from the Galileo system, thus increasing the likelihood of detecting spoofing attacks at the data level and significantly contributing to the security of the solution. The OSNMA public observation phase is currently ongoing (gsc-europa.eu/support-to-developers/osnma-public-observation-test-phase). As part of that, the final OSNMA signal in space (SiS) interface control document (ICD) was published in December 2022, while the broadcast of a compliant SiS together with test certificates for the public key infrastructure started in August, marking the start of the OSNMA initial operational capability. The OSNMA initial service declaration will be achieved after the completion of the service validation activities and is targeted for early 2024.

Safety of life

The Galileo contribution to safety of life services (GoSoL) will cover the provision of Galileo signals and of service guarantees to enable the implementation of horizontal ARAIM service supporting aviation users. The service roadmap is currently under definition with a stepwise approach that will include the broadcast of a test ISM before the operational service is provided.

SAR

SAR/Galileo provides accurate, timely, and reliable distress alert data to help rescue authorities assist in distress situations (forward link service). It also acknowledges the receipt of the distress forward link alert to the beacon in distress via the Galileo navigation SiS (return link service). SAR/Galileo is a geographically distributed system, which was extended with a fourth European MEOLUT installed in La Reunion, in operation since November 2022.

The combination of SAR/Galileo space and ground assets provides excellent performance levels with a mean location accuracy of less than 800 m and a return link delivery latency of less than 1 min, which assisted in the rescue of approximately 1,400 people within EU territories in 2022.

Utilizing the return link service capabilities brings new innovations that further contribute to the global emergency space operations as Galileo moves forward to the implementation phase of the emergency warning satellite service (EWSS). The EWSS will provide national civil protection authorities with a satellite broadcasting capability to broadcast on-demand authenticated alerts to a precise target area and its population directly to any device capable of processing Galileo signals.

Reference documents for each of the above services can be found at the EUSPA European GNSS Service Center website, including technical notes, interface control documents and service declaration documents.

Image: European Space Agency (ESA)

Full operational capability infrastructure development toward completion

Space segment

The production of the third batch of Galileo FOC satellites, by the satellite manufacturer OHB Systems, has been completed for an overall amount of 12 satellites. The acceptance review for the last couple of spacecraft took place in June.

This amounts to an overall production by OHB Systems of 34 Galileo FOC Satellites (14 satellites in batch one, eight satellites in batch two and 12 satellites in batch three) of which 24 are in orbit. The remaining 10 satellites are in storage waiting for the next launch opportunity in 2024.

Ground segment

G2SB1 engineering model payload testing at ESA ESTEC. (Image: ESA)

The ground segment is going through a major upgrade with the roll-out of the new System Build 2.0 infrastructure in support of public regulated service IOC and open service FOC.

The new version of the ground mission segment developed by Thales Alenia Space France will be oriented to increase service robustness and resilience, besides high performance. It will provide virtualized hardware and software infrastructure at the Galileo Control Centers, triple receiver chain redundancy in the sensor stations’ remote sites and two additional sites located in Wallis (Pacific Ocean) and Bonaire (Caribbean Sea) to increase global coverage with 15 sites overall. A new mission monitoring capability has been implemented for the operators using the SAFE/Agile methodology. Furthermore, a system extended contingency mode will be implemented to cope with outages lasting up to seven days with smooth navigation performance degradation.

A new version of the Galileo Security Facility will be deployed at the Galileo Security Monitoring Centers offering an evolution of the public regulated service (PRS) capabilities through new enhanced SiS access control. Furthermore, a new state of the art cyber security monitoring system will be implemented.

The System Build 2.0 infrastructure qualification was completed by ESA in July. Migration in operation is based on an innovative concept consisting of a replica of the operational chains to ensure seamless transition from the current system in operation to the newly deployed one. The completion of the migration into operations is planned for the beginning of 2024, with the schedule being continuously monitored at the program level.

Galileo Second Generation: a constellation of state-of-the-art procurements. (Image: ESA)

An upgrade of the ground control segment in charge of command and control of the constellation is under qualification by the industrial consortium led by GMV. It will provide additional flexibility to allow for deployment in between launches and to address resolution of hardware and software obsolescence, including cyber security, operability improvements and a security monitoring overlay. Furthermore, it will upgrade the Telemetry Tracking and Control (TTC) station in Redu, Belgium, and deploy an additional station in Fucino, Italy, co-located with the Galileo Control Center, bringing to nine the overall number of TTC stations.

Second generation fast forward

Galileo’s second generation (G2G) will introduce many innovative technologies to offer unprecedented precision, robustness, and flexibility.

For the development of G2G activities 2023 was a key year, with the development of the first batch of G2 satellites, the start of all contracts for in-orbit validation of the ground segment and system test beds and the preparation of the initial operational capability (IOC) design, through the consolidation of the mission/service roadmaps with the EC, EUSPA, and the delegates from EU member states.

This year, Europe has taken the necessary steps to unchain the development of key GNSS features, which will exponentially enhance GNSS accuracy for the worldwide communities in the future:

• New and improved services.
• Unique flexibility of ground and space systems to enable 12-18 months service time to market, without the need for constellation replenishment.
• Upgraded robustness of key infrastructure items.
• State of the art GNSS technology leading to centimeter-level precision.
• New GNSS signals, including extended data capacity for added value services.
• And of course, as a key factor, a full backward compatibility with Galileo First Generation and other GNSS systems.

G2G: Incremental steps for enhanced capabilities over the next decade

The ESA completed the G2G system preliminary design review in July, focused on three key incremental phases of the G2G:

• G2G In-Orbit Validation (G2GIOV): specification, design and validation activities for the sake of ensuring the full development of the first batch of G2G satellites and all the associated infrastructure for launch and early orbit phase, in-orbit testing, in-orbit validation, initial enhancement of Galileo services and addition of new Galileo service components.
• G2G Initial Operational Capability (G2GIOC): design and specifications required for the complementary procurements that will ensure new Galileo services, as enabled by G2G infrastructure, including both the second batch of G2G satellites and the G2G ground segment.
• G2G Full Operational Capability (G2GFOC): Identification of key technological enablers and additional capabilities required for final G2G implementation, including the bridge to future synergies with other EU and ESA programs.

G2G in-orbit validation infrastructure – satellite hardware under validation

G2SB1 acoustic testing in Rome and structural model arrival at ESA ESTEC. (Image: ESA)

The two parallel contracts with Thales Alenia Space and Airbus to develop and manufacture each of six G2G batch one satellites (G2SB1A and B) achieved key milestones this year.

On the G2SB1 satellite A side, the prime contractor tested engineering model payloads and structural models at its premises and delivered them to ESA’s Technology Center (ESTEC). The validation of the new G2G payload capabilities and the key mechanical, vibration and acoustical testing milestones have been achieved.

These satellites will provide the following key innovations: reconfigurable fully digital navigation payload; point-to-point connection between satellites by inter-satellite-link for command and control, and ranging functionalities; electric propulsion for orbit-raising capabilities; advanced jamming and spoofing protection mechanisms; on-board authentication capabilities; increased ground-to-space data rate; and improved time reference (number of clocks and advanced clock monitoring functions).

Key mechanical and launch-related tests on the structural models stacked configurations were performed in the last quarter of this year, in order to simulate the launcher environment and satellite separation dynamics.

On the G2SB1 satellite B and the PHM and RAFS clock manufacturing sides, activities are ongoing as planned, with key HW infrastructure developed and tested in the respective Industrial Primes premises.

This included as key events in 2023 the full testing of the satellite advanced engineering model antenna and the creation of a satellite atomic clock farm in industry premises to produce the more than 70 atomic clocks required for the 12 G2 batch one satellites.

The next steps for these contracts are the completion of the equipment and satellite CDRs, expected in the coming months, in order to engage (starting at the end of 2024) with the critical system compatibility test campaigns of the G2G IOV ground segment infrastructure and system engineering test beds under development.

Galileo Second Generation batch one satellites. (Image: ESA)

G2G in-orbit validation infrastructure – ground segment and test beds in full development

The key system engineering, ground segment and test beds infrastructure procurements were all awarded during the first semester of 2023, giving EC/EUSPA/ESA and the industrial teams a brief moment of respite and celebration.

Following a competition process that encompassed about 12 months of detailed technical, management and legal interactions, 11 industrial prime contractors were selected for a set of contracts engaging about $1 billion euros of public sector investment:

• Four contracts for system engineering, signal and performance, system validation and security and PRS activities.
• Four contracts for ground segment in-orbit validation infrastructure.
• Three contracts for system test bed activities plus a series of technological developments in the receivers and constellation simulation side.
• Once completed in the years to come, these infrastructure developments will ensure not only the launch and early orbit phasing and in-orbit validation of the novel G2G satellite’s capabilities, but also enable the provision to all world users of enhanced Galileo services.

G2G satellites stacked configuration for launcher simulated test at ESA ESTEC. (Image: ESA)

G2G initial and final operational capability moving ahead

In line with the outcomes of the system preliminary design review, two new lines of GNSS improvements are well underway at program level.
In the area of G2G initial operational capability (IOC), which will provide new G2G initial services, an extensive preparatory work has been performed by EUSPA in order to derive the mission needs (as defined by the EC and its Member States), into a set of service evolution roadmaps for the more than one dozen Galileo services.

This work has been supported by ESA dossiers providing incremental implementation of these services, in a continuous improvement ramp-up process, which guarantees backward compatibility and seamless enhancement.

The relevant procurements that will enable, in combination with the in-orbit validation infrastructure, the provision of these services are currently under consolidation:

• G2G IOC ground segment, with an initial version to be procured in 2024.
• G2G satellites batch two, which is expected to start its competitive procurement procedure in the second part of the EU’s 2021-2028 multi-financial framework.

In addition, work is well advanced in the definition of the key technological developments and system trade-offs that will be analyzed for inclusion in the G2G final operational capability (FOC), expected early in the 2030s.

Critical technologies being analyzed include optical inter-satellite links, advanced governmental payloads, new ground segment and signal technologies and in-space constellation monitoring, among others. ESA expects to complete the preparation of the system-critical design review by the end of 2024 or early 2025 and to submit it for in-depth review by the EC, EUSPA and European member states stakeholders.

Conclusions

Galileo keeps providing continuous and stable services to users with new enhanced capabilities offering high accuracy, authentication and faster time to first fix. The space and ground infrastructure development for the first generation is progressing toward public regulated service IOC and open service FOC.
In parallel, for G2G, hardware production of the new satellites is well under way and the ground segment development has started to maintain Galileo competitive with the other GNSS.

We continue to strive toward achieving the vision defined at the end of the previous decade: “If you can imagine a novel satellite navigation service, we will implement it in 12-18 months.”

We have an exciting road ahead.

G2G FOC perspectives. (Image: ESA)

<p>The post Galileo: An exciting road ahead toward new capabilities first appeared on GPS World.</p>

In which markets and/or applications do you specialize?

We originally designed our LabSat simulator for ourselves, because we supply GPS equipment to the automotive market. Then, we decided to sell it into that market, which is our primary market, for other people to use. That’s where we started, but it has moved on since then. We supply many of the automotive companies who use it for testing their in-car GPS-based navigation systems.

However, we’ve moved on to our second biggest market, which is the companies that make deployment systems for internet satellites, which use it for end-of-life testing. Several of our customers use it. That’s because we do space simulations, so we can simulate the orbits of satellites. That’s very useful when they’re developing their satellites.

We supply many of the major GPS board manufacturers — such as NovAtel, Garmin, and Trimble — when they’re developing their boards and testing their devices. We supply many of the phone companies — such as Apple and Samsung — and many of the GPS chip manufacturers — such as Qualcomm, Broadcom, and Unicom. More or less any company that’s into GNSS.

How has the need for simulation changed in the past five years, with the completion of the BeiDou and Galileo GNSS constellations, the rise in jamming and spoofing threats, the sharp increase in corrections services, and the advent of new LEO-based PNT services?

It all started off very simple, with just GPS, which was one signal and one frequency. We got that up and working very well and it helped us a lot. Then we got into this market. In the last few years, we’ve had to suddenly invent 15 new signals. We do two systems, really: one is a record-and-replay system. You put a box in a car, on a bike, in a backpack, or on a rocket, and you record the raw GPS signals; then you can replay those on the bench. That requires greater bandwidth, greater bit depth, smaller size, battery power, all of that.

The other is pure signal simulation. We simulate the signals coming from the satellites from pure principles. So, we’ve had to dive into how those signals are structured, reproduce them mathematically, and then incorporate that in into our software. That’s been 15 times the original work we thought it would be, but as we add each signal it tends to get a bit simpler until they add new ways to encode signals, and then it gets complex again. We’ve had to increase our bandwidth, increase our bit depth for the recording to cover all of these new signals.
Because our systems record and replay, they’re used a lot to record real-world jamming. In many scenarios, our customers will take one of our boxes into the field and record either deliberate jamming or jamming that’s been carried out by a third party. Then they can replay that in the comfort of their lab.

With regards to spoofing, we’ve just improved our signal simulation. So, we can completely synchronize it with real time. We can do seamless takeover of a GNSS signal in real time. We can reproduce the current ephemeris and almanac. If we transmit a sufficiently powerful signal, we can completely take over that device. Then we can insert a new trajectory into it. That’s a very recent update we’ve done.

If the complexity and amount of your work has gone up so much in the last few years but you cannot increase your prices at the same rate, what does that do to your business model?

It’s the same people that produce the signals in the first place, so they still have a job. However, as we add more signals and capabilities, we tend to get more customers as well.

Oh, so, you’re expanding your market!

Right, right.

Regarding some of the new PNT services being developed, how do you simulate them realistically without the benefit of recordings of live sky signals?

It is all pure signals simulation. You go through the ICD line-by-line and work out the new schemes. Here’s an interesting anecdote. Our developer who does a lot of the signal development is Polish and is also fluent in Russian. When we were developing the GLONASS signals, he was working from the English version of the GLONASS ICD. He said that it didn’t make any sense. So, he looked at the Russian version and discovered that the English one had a typo. When he used the Russian version, everything worked perfectly. He told this to his contacts at GLONASS and they thanked him and updated the English translation of their document. So, you are very, very much reliant on every single word in that ICD.

Are there typically differences between the published ICD and the actual signal?

No, no. Apart from the Russian one, which had a typo, they’re very good. For example, we’ve recently implemented the latest GPS L1C signal. My developer spent six months recreating it and getting all the maths right and the only way you could test it was to connect it to a receiver and hit “go.” It just worked the first time. He almost fell off his chair. The ICD in that case was very, very accurate.

Hope that Xona’s ICD is just as good.

Yeah.

Are accuracy requirements for simulation increasing, to enable emerging applications?

Yes, absolutely. No one can have too much accuracy. Everyone’s chasing the goal of getting smaller, faster, and more accurate systems. They want greater precision and better accuracy from their simulators, as well as a faster response. We do real-time simulators and they want a smaller and smaller delay from when you input the trajectory to when you get the output. Luckily for us, Moore’s law is still in effect, so, as the complexity of the signals and the accuracy requirements increase, computers can churn through more data. Luckily, we’re able to keep up on the hardware side as well, because much of our processing is done using software. Some companies do it in hardware and some companies do it in software. We concentrate on the software side of things.

Here’s another interesting anecdote from my Polish guy. He noticed that the latest Intel chips contain an instruction that multiplies and divides at the same time but that it wasn’t available in Windows. So, he put in a request with Microsoft for that operational code and they incorporated it into the very latest version of dotnet, which has improved our simulation time by 7%. I see little improvements like that all the time.

Are all your simulators for use in the lab or are some for use in the field? If the latter, for what applications and how do they differ from the ones in the lab? (Well, for starters, I assume that they are smaller, lighter, and less power-hungry…)

All our systems are designed to be used inside and outside the lab. They can all be carried in a backpack, on a push bike, in a car. We do that deliberately, because we come from the automotive side of things, so we have to keep everything very small and compact.

Besides automotive, what are some field uses?

Some of our customers have put them in rockets, recording the signal as it goes up, or in boats. We have people walking around with an antenna on their wrist connected to one of our systems, so that they can simulate smartwatches. There are many portable applications. We have a very small battery-powered version, which makes it very independent.

Are there any recent success stories that you are at liberty to discuss?

Our most exciting one is a seamless transition for simulation that we developed to replace or augment GPS in tunnels. We’ve been talking to many cities around the world that are building new tunnels. Because modern cars automatically call emergency services when they crash or deploy their airbags, they need to know where they are, of course. Cities need to take this into account when they are building new tunnels, which can pass over each other or match the routes of surface streets. Therefore, accurate 3D positioning in the tunnels has become essential. It requires installing repeaters every 30 meters along each tunnel and software that runs on a server and seamlessly updates your position every 30 meters. As you enter a tunnel, your phone or car navigation system instantly switches to this system. It’s been received very well because it’s mainly software and the hardware is pretty simple. We’ve brought the cost down to a fifth of the cost of standard GPS simulators for tunnels. So, we’re talking to several cities about some very long tunnels, which is very exciting.

<p>The post Faux signals for real results: Racelogic first appeared on GPS World.</p>