SPACE/COSMOS
LEO satellites show promise to boost navigation accuracy where GPS struggles
image:
Gain in the lower-bound positioning accuracy with respect to GPS+Galileo for hybrid combinations of medium-sized LEO and GNSS.
view moreCredit: The authors
Precise positioning is increasingly critical for applications ranging from autonomous mobility to resilient infrastructure monitoring. Current Global Navigation Satellite Systems (GNSS) provide global coverage but often suffer from weak signals, urban multipath, and interference vulnerabilities. A new study conducted extensive simulations on Low Earth Orbit (LEO) satellite-based Positioning, Navigation and Timing (PNT) systems across representative outdoor environments. The research evaluated signal power, geometry quality, positioning accuracy and interference robustness under different carrier frequencies, satellite transmission powers and constellation designs. Results show that optimized LEO constellations, particularly in hybrid mode with GNSS, significantly improve accuracy and maintain strong performance in urban scenarios where GNSS degrades.
Current Global Navigation Satellite Systems (GNSS) has supported global Positioning, Navigation and Timing (PNT) services for decades, but modern applications demand higher reliability, faster convergence, and resistance to jamming and spoofing. In dense cities or partially blocked environments, GNSS signal strength drops and multipath error increases, limiting accuracy. Meanwhile, global reliance on GNSS raises security risks should interference disable navigation. Low Earth Orbit (LEO) systems have emerged as a promising alternative, offering higher received power, better satellite geometry and broader spectrum options. Due to these challenges, researchers aim to evaluate whether LEO-PNT can complement or enhance GNSS performance through large-scale simulations and design comparisons; based on these issues, further in-depth research is necessary.
Researchers from Tampere University and Universitat Autònoma de Barcelona published (DOI: 10.1186/s43020-025-00186-5) a comparative analysis in December 2025 in Satellite Navigation. The study investigates how different LEO constellation configurations perform in positioning accuracy and interference robustness when operating alone or jointly with GNSS. Using semi-analytical modelling and 192,000 Monte-Carlo simulations, the team evaluated 400 users across European regions in five outdoor scenarios. Key variables included carrier bands (1.5/5/10 GHz), Effective Isotropic Radiated Power levels and constellation geometry design.
The team simulated multiple standalone and hybrid constellation architectures, analysing Carrier-to-Noise Ratio (C/N0), Geometric Dilution of Precision (GDOP), Position Dilution of Precision (PDOP) and lower-bound 3D accuracy. Results indicate that an EIRP of 50 dBm is sufficient for high-quality outdoor positioning when operating in L- and C-bands. While 10 GHz platforms require higher power to compensate path loss, hybrid LEO+GNSS modes show markedly improved stability and reliability.
Multi-shell constellations such as Çelikbilek-1 and Marchionne-2 delivered a favorable balance between satellite count and global geometry, outperforming single-shell layouts. In harsh urban canyon conditions, GNSS accuracy degraded up to seven-fold, whereas LEO-PNT maintained stable ranging performance with limited loss. Interference resistance also improved: stronger LEO signal power means jammers require far greater intensity to cause equal degradation. Hybrid designs provided the most significant gains. Combinations such as Çelikbilek-1 + Global Positioning System (GPS)/Galileo, or CentiSpace-like + BeiDou, yielded better PDOP distributions, faster fix availability and broader user coverage. The authors conclude that LEO systems are not aimed at replacing GNSS, but rather to enhance availability and resilience under signal-challenged environments.
"Our results show that moderate-power LEO constellations can substantially strengthen outdoor positioning without requiring expensive satellite hardware," the authors noted. "Geometry plays a major role—carefully designed multi-shell constellations achieve strong accuracy even with fewer satellites. As LEO-PNT develops, hybrid integration with GNSS offers the most cost-effective path toward secure, robust PNT solutions. This work provides guidance for future system designers evaluating frequency, transmission power and constellation configuration trade-offs."
The findings suggest a realistic rollout pathway for resilient satellite navigation. LEO-enhanced PNT could benefit autonomous vehicles, UAV routing, emergency response, precision farming and critical infrastructure monitoring—especially where GNSS falters in interference-dense or high-rise environments. Lower-power LEO transmission also reduces deployment cost, opening access for commercial operators. Future work may assess indoor positioning potential, bandwidth expansion, and real-orbit testing to refine simulation assumptions. As global demand for secure PNT grows, the integration of LEO and GNSS could become a cornerstone for next-generation navigation technology.
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References
DOI
Original Source URL
https://doi.org/10.1186/s43020-025-00186-5
Funding information
This work has been supported by Tampere University's Dean's PhD grant. This work has also been partially supported by the LEDSOL project funded within the LEAP-RE programme by the European Union's Horizon 2020 Research and Innovation Program under Grant Agreement 963530, by the Research Council of Finland grant 352364, and by the Spanish Agency of Research (AEI) under grant PID2023- 152820OB-I00 funded by MICIU/AEI/10.13039/501100011033 and by ERDF/EU, and grant PDC2023-145858-I00 funded by MICIU/AEI/10.13039/501100011033 and by the European Union NextGenerationEU/PRTR.
About Satellite Navigation
Satellite Navigation (E-ISSN: 2662-1363; ISSN: 2662-9291) is the official journal of Aerospace Information Research Institute, Chinese Academy of Sciences. The journal aims to report innovative ideas, new results or progress on the theoretical techniques and applications of satellite navigation. The journal welcomes original articles, reviews and commentaries.
Journal
Satellite Navigation
Subject of Research
Not applicable
Article Title
A Comparative study on ranging accuracy and interference robustness of LEO-PNT systems in urban and rural scenarios
Article Publication Date
15-Dec-2025
SwRI-led PUNCH mission producing unprecedented images of Sun
NASA spacecraft also tracks space weather events, comets and more
video:
With less than a year in orbit, the Southwest Research Institute-led PUNCH mission has made major accomplishments, imaging the Sun in context while tracking comets and enormous space weather events as they traveled through the inner solar system. In addition to showing the Sun’s activity, this movie tracks the Moon moving across the field of view, the planets Venus, Mercury, and Mars lined up in the ecliptic plane, various constellations, the Milky Way galaxy, and Comet Lemmon (top) traveling through the inner solar system.
Credit: Southwest Research Institute
SAN ANTONIO — December 16, 2025 — After less than a year in orbit, the Southwest Research Institute-built PUNCH spacecraft have made major accomplishments, imaging the Sun in context while tracking comets and enormous space weather events as they traveled through the inner solar system. SwRI’s Dr. Craig DeForest discussed the achievements of NASA’s PUNCH (Polarimeter to Unify the Corona and Heliosphere) mission during a media roundtable at the AGU25 conference on Dec. 16.
“PUNCH imaging gives us a unique view on the pageantry of the planets and reveals the grandeur of our Sun in the cosmos,” said DeForest, PUNCH mission principal investigator. “Seeing solar activity sweeping across the moon, planets and even passing comets gives us a sense of place in our solar system. It reminds me of the impact of the blue marble image of the Apollo era, though PUNCH data is more of a golden fishbowl view of our neighborhood in the cosmos. We live here.”
Since PUNCH’s four small suitcase-sized spacecraft launched on March 11, they have synched up to act as a single virtual instrument 8,000 miles across. In addition to imaging the Sun’s outer atmosphere as it transitions into the solar wind, PUNCH has tracked enormous coronal mass ejections flinging solar particles across the sky and washing over the Earth.
“PUNCH can actually show us directly the violence of space weather as clouds of electrons cross the solar system,” DeForest said. “Viewing the corona and solar wind as a single system provides a big-picture perspective essential to helping scientists better understand and predict space weather. This forecasting is critical to protecting astronauts, space satellites and electric grid technology from these events.”
The SwRI-developed and -led Wide Field Imagers are aboard three of the four PUNCH spacecraft collecting high-resolution images of entire coronal mass ejections (CMEs) in greater detail than previously possible. These instruments are designed to observe the faint, outermost portion of the Sun’s atmosphere and solar wind. The PUNCH science team is working to integrate data from its coronagraph, the Narrow Field Imager provided by the Naval Research Laboratory, from aboard the fourth spacecraft into the overall data products.
“The NASA Small Explorer’s mission had a bird’s-eye view of the CME in early November that lit up skies across the nation with colorful aurora,” DeForest said. “And we’ve discovered some incredible bonus science that PUNCH performs, tracking comets and other objects. We were able to track the third identified interstellar comet 3I/ATLAS as it traveled through the inner solar system while bright sunlight rendered it invisible to other telescopes and space assets.”
In what may be the longest continuous observation of a comet to date, PUNCH also monitored Comet SWAN with unprecedented frequency, clearly imaging the object every four minutes for nearly 40 days, from Aug. 25 to Oct. 2. PUNCH is also tracking Comet Lemmon, which made its closest approach to Earth on Oct. 21.
SwRI’s Solar System Science and Exploration Division leads the PUNCH mission and operates the four spacecraft from its facilities in Boulder, Colorado. The Boulder division is part of SwRI’s Space Sector, based in San Antonio, Texas. The mission is managed by the Explorers Program Office at NASA Goddard Space Flight Center in Greenbelt, Maryland, for the Science Mission Directorate at NASA Headquarters in Washington.
For more information, visit https://www.swri.org/markets/earth-space/space-research-technology/space-science/heliophysics.
Click here to watch a video about PUNCH: https://youtu.be/6Kk05oIEeJ0.
Supernova from the dawn of the universe captured by James Webb Space Telescope
An international team of astronomers has achieved a first in probing the early universe
UCD Research & Innovation
An international team of astronomers has achieved a first in probing the early universe, using the James Webb Space Telescope (JWST), detecting a supernova – the explosive death of a massive star – at an unprecedented cosmic distance.
The explosion, designated SN in GRB 250314A, occurred when the universe was only about 730 million years old, placing it deep in the era of reionisation. This remarkable discovery provides a direct look at the final moments of a massive star from a time when the first stars and galaxies were just beginning to form.
The event, which has been reported on in the recently published academic paper ‘JWST reveals a supernova following a gamma-ray burst at z ≃ 7.3,’ (Astronomy & Astrophysics, 704, December 2025), was initially flagged by a bright burst of high-energy radiation, known as a long-duration Gamma-Ray Burst (GRB), detected by the space-based multi-band astronomical Variable Objects Monitor (SVOM) on March 14, 2025. Follow-up observations with the European Southern Observatory’s Very Large Telescope (ESO/VLT) confirmed the extreme distance.
The key finding came from targeted observations with JWST's Near-Infrared Camera (NIRCAM) approximately 110 days after the burst. Scientists were able to separate the light of the explosion from its faint, underlying host galaxy.
Co-author, and astrophysicist at UCD School of Physics, Dr Antonio Martin-Carrillo said: “The key observation, or smoking gun, that connects the death of massive stars with gamma-ray bursts is the discovery of a supernova emerging at the same sky location. Almost every supernova ever studied has been relatively nearby to us, with just a handful of exceptions to date. When we confirmed the age of this one, we saw a unique opportunity to probe how the Universe was there and what type of stars existed and died back then.
“Using models based on the population of supernovae associated with GRBs in our local universe, we made some predictions of what the emission should be and used it to proposed a new observation with the James Webb Space Telescope. To our surprise, our model worked remarkably well and the observed supernova seems to match really well the death of stars that we see regularly. We were also able to get a glimpse of the galaxy that hosted this dying star.”
The data indicate that the distant supernova is surprisingly similar in brightness and spectral properties to the prototype GRB-associated supernova, SN 1998bw, which exploded in the local universe.
This similarity suggests that the massive star that collapsed to create GRB 250314A was not significantly different from the progenitors of GRBs observed locally, despite the vastly different physical conditions (such as lower metallicity) in the early universe. The observations also ruled out a much more luminous event, such as a Superluminous Supernova (SLSN).
The findings challenge the assumption that the stars of the early universe, formed under extremely low-metallicity conditions, would lead to markedly different, perhaps brighter or bluer, stellar explosions than those seen today.
While this discovery provides a powerful anchor point for understanding stellar evolution in the early universe, it also opens new questions about the observed uniformity.
The research team plans to secure a second epoch of JWST observations in the next one to two years. By that time, the supernova light is expected to have faded significantly (by over two magnitudes), allowing the team to completely characterise the properties of the faint host galaxy and confirm the supernova's contribution.
Journal
Astronomy and Astrophysics
Method of Research
News article
Subject of Research
Not applicable
Article Title
JWST reveals a supernova following a gamma-ray burst at z ≃ 7.3
Article Publication Date
9-Dec-2025
Seeing the Ionosphere in motion: A new
way to track space weather in real time
Aerospace Information Research Institute, Chinese Academy of Sciences
image:
The location of the receivers. The pseudo-color indicates the mean elevation angle of the LOS from the GEO satellite C03 to each receiver on 2024-09-21. The gray line marks the mean sub-satellite longitude of C03.
view moreCredit: Satellite Navigation
Accurate, real-time monitoring of ionospheric dynamics is essential for understanding space weather and protecting satellite-based navigation and communication systems. A new study introduces an innovative observation framework that captures rapid and fine-scale ionospheric variations by directly measuring spatial and temporal gradients of total electron content. By exploiting a stable geometric configuration between geostationary satellites and ground-based receivers, the approach achieves high spatial resolution and continuous temporal coverage without relying on interpolation or satellite motion corrections. This enables the detection of ionospheric structures across multiple scales, from gradual daily evolution to fast-developing disturbances, offering a more precise and dynamic view of ionospheric behavior than existing monitoring techniques.
The ionosphere is a highly dynamic region shaped by solar radiation, geomagnetic activity, and atmospheric processes, and its variability can severely disrupt satellite navigation and communication signals. Traditional monitoring methods face inherent trade-offs: low-Earth and medium-Earth orbit satellites provide limited temporal continuity, while ground-based instruments offer only regional coverage. Global ionospheric maps, though comprehensive, often smooth out short-lived or fine-scale disturbances. As a result, critical processes such as equatorial ionization anomalies, plasma instabilities, and traveling ionospheric disturbances are difficult to observe in real time and with sufficient resolution. Based on these challenges, there is a pressing need to develop advanced monitoring frameworks capable of resolving ionospheric dynamics across both space and time.
Researchers from Sun Yat-sen University and the Chinese Academy of Sciences, together with international collaborators, report a new ionospheric monitoring framework in a study published (DOI: 10.1186/s43020-025-00187-4) in Satellite Navigation in 2025. The team developed a fixed-geometry observation network using geostationary Earth orbit satellites and dense ground-based GNSS receiver arrays. By focusing on ionospheric gradient measurements rather than traditional point observations, the study demonstrates a new way to observe ionospheric evolution with unprecedented spatiotemporal resolution and consistency.
The new framework leverages the stationary geometry between geostationary satellites and ground receivers to form dense, fixed ionospheric pierce points connected by geometry-invariant baselines. Each baseline acts as an independent sensing unit, allowing researchers to directly estimate spatial and temporal gradients of total electron content at a resolution finer than 0.25° and a time step of 30 seconds. Unlike conventional methods, this approach avoids errors introduced by satellite motion and interpolation smoothing.
Using several case studies, the researchers demonstrated the framework’s capability to capture complex ionospheric phenomena. During the daily evolution of the equatorial ionization anomaly, the method resolved sharp gradient structures and tracked crest migration in near real time. For equatorial plasma bubbles, the system identified steep density gradients and nonlinear plasma instabilities, revealing their growth, drift, and dissipation with high precision. The framework also successfully characterized large-scale traveling ionospheric disturbances during geomagnetic storms, capturing their propagation speed, wavelength, and interaction with background ionospheric structures. Together, these results show that gradient-based monitoring can reveal both linear and nonlinear ionospheric processes that are often obscured in traditional observations.
“This framework fundamentally changes how we observe the ionosphere,” said one of the study’s authors. “By focusing on geometry-consistent gradient measurements, we can directly track how plasma structures evolve in space and time, rather than inferring them from sparse snapshots. This allows us to distinguish between gradual transport processes and rapidly developing instabilities, offering a much clearer physical interpretation of ionospheric behavior, especially during disturbed space weather conditions.”
The proposed approach provides a scalable and cost-effective foundation for continental-scale ionospheric monitoring and real-time space weather diagnostics. Its high resolution and continuity make it particularly valuable for early warning of ionospheric disturbances that degrade GNSS positioning accuracy and communication reliability. Beyond operational applications, the framework opens new possibilities for studying ionospheric coupling processes, validating ionospheric models, and improving mapping functions used in navigation systems. As global GNSS and geostationary satellite infrastructures continue to expand, this method could play a key role in building long-term, high-resolution ionospheric datasets to support both scientific research and practical space weather services.
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References
DOI
Original Source URL
https://doi.org/10.1186/s43020-025-00187-4
Funding Information
This work was supported by the National Natural Science Foundation of China (42374181, 42374186, 42441814), Key Innovation Team of China Meteorological Administration ‘Space Weather Monitoring and Alerting’ (CMA2024ZD01), ‘Ionospheric Forecast and Alerting’ Youth Innovation Team (CMA2024QN09), Shandong Key R&D Program (2024CXGC00116) and Jinan Haiyou Leading Talents Of Industry.
About Satellite Navigation
Satellite Navigation (E-ISSN: 2662-1363; ISSN: 2662-9291) is the official journal of Aerospace Information Research Institute, Chinese Academy of Sciences. The journal aims to report innovative ideas, new results or progress on the theoretical techniques and applications of satellite navigation. The journal welcomes original articles, reviews and commentaries.
Journal
Satellite Navigation
Subject of Research
Not applicable
Article Title
Ionospheric gradient estimation using ground-based GEO observations for monitoring multi-scale ionospheric dynamics
Article Publication Date
8-Dec-2025
Exploring the origins of the universe: 145 low-noise amplifiers complete ALMA telescopes
Fraunhofer IAF and Max Planck Institute for Radio Astronomy provide modules for Band 2 receivers
image:
ALMA telescope array in the Atacama Desert
view moreCredit: © ESO/C.Malin
The Atacama Large Millimeter/Submillimeter Array (ALMA) in the Chilean Andes is one of the most powerful radio telescope facilities in the world. Researchers use it to study dark and distant regions of the universe in order to better understand how stars, planets, galaxies and life itself are formed. To do this, ALMA measures the millimeter and submillimeter radiation emitted by cold molecular clouds, for example. Molecular clouds are interstellar gas clouds with a temperature of only a few tens of Kelvin, in which stars form when the density and temperature are right.
ALMA has a total of 66 individual parabolic antennas with diameters of 12 m or 7 m, each equipped with high-frequency receivers for ten wavelength ranges (›ALMA bands‹) between 6 and 8.6 mm (35–50 GHz) and 0.3 and 0.4 mm (787–950 GHz) in the electromagnetic spectrum. For Band 2, which covers wavelengths from 2.6 to 4.5 mm (67–116 GHz), the Fraunhofer Institute for Applied Solid State Physics IAF and the Max Planck Institute for Radio Astronomy (MPIfR) have now provided 145 low-noise amplifiers (LNAs). This means that all ALMA bands are now fully equipped for the first time.
With ALMA’s Band 2, researchers hope to gain a better understanding of the so-called cold interstellar medium — a mixture of dust, gas, radiation and magnetic fields from which stars are formed. Complex organic molecules in nearby galaxies, which are considered precursors to biological building blocks, as well as planet-forming disks, will also be studied in greater detail thanks to the improved measurement capabilities.
Unique average noise temperature of 22 K enables highly sensitive measurements in band 2 of the ALMA telescopes
“The performance of receivers depends largely on the performance of the first high-frequency amplifiers installed in them,” explains Dr. Fabian Thome, head of the subproject at Fraunhofer IAF. “Our technology is characterized by an average noise temperature of 22 K, which is unmatched worldwide.” With the new LNAs, signals can be amplified more than 300-fold in the first step. “This enables the ALMA receivers to measure millimeter and submillimeter radiation from the depths of the universe much more precisely and obtain better data. We are incredibly proud that our LNA technology is helping us to better understand the origins of stars and entire galaxies.”
“This is a wonderful recognition of our fantastic collaboration with Fraunhofer IAF, which shows that our amplifiers are not only ‘made in Germany’ but also the best in the world,” says Prof. Dr. Michael Kramer, executive director at MPIfR.
Development, production and qualification of InGaAs mHEMT LNAs for ALMA
At the heart of the LNAs for ALMA’s Band 2 are monolithic microwave integrated circuits (MMICs) based on metamorphic high-electron-mobility transistors (mHEMTs) developed by Fraunhofer IAF using the compound semiconductor material indium gallium arsenide (InGaAs). The technology enables LNAs with particularly low noise temperatures, which significantly increases the sensitivity of the receivers. As the name suggests, low-noise amplifiers improve the quality of incoming signals by amplifying the signal while causing as little disruptive background noise as possible.
Fraunhofer IAF and MPIfR were jointly commissioned by the European Southern Observatory (ESO), which operates ALMA in cooperation with other international institutions. Fraunhofer IAF was responsible for the specific design of the MMICs, their manufacturing, their testing at room temperature and the selection of the chips. MPIfR took over the modules’ complex assembly and qualification, including cryogenic test measurements at 15 K for use in the ALMA Band 2 receivers matching ESO specifications.
Location and operation of ALMA
In order to perform the most accurate measurements possible, ALMA was built on the Chajnantor Plateau in the Chilean Andes. In the Atacama Desert, at an altitude of 5000 m above sea level, conditions for radio astronomical measurements are unique in the world. The high altitude and dry location ensure that millimeter and submillimeter radiation from distant regions of the universe is significantly less attenuated than elsewhere, as it has to penetrate less atmospheric water vapor.
ALMA is jointly operated by ESO, the US National Science Foundation (NSF) and the Japanese National Institutes of Natural Sciences (NINS) in cooperation with the Republic of Chile. ALMA is supported by ESO on behalf of its member countries (Belgium, Denmark, Germany, Finland, France, Great Britain, Ireland, Italy, the Netherlands, Austria, Poland, Portugal, Spain, Sweden, Switzerland, the Czech Republic, and the host country Chile), by the NSF in collaboration with the Canadian National Research Council (NRC), the Taiwanese National Science Council (NSC) and NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).
About Fraunhofer IAF
The Fraunhofer Institute for Applied Solid State Physics IAF is one of the world's leading research institutions in the fields of III-V semiconductors and synthetic diamond. Based on these materials, Fraunhofer IAF develops components for future-oriented technologies, such as electronic circuits for innovative communication and mobility solutions, laser systems for real-time spectroscopy, novel hardware components for quantum computing as well as quantum sensors for industrial applications. With its research and development, the Freiburg research institute covers the entire value chain — from materials research, design and processing to modules, systems and demonstrators. https://www.iaf.fraunhofer.de/en.html
Further information
https://www.eso.org/public/unitedkingdom/teles-instr/alma/?lang – Learn more about ALMA
https://www.iaf.fraunhofer.de/en/researchers/electronic-circuits.html – More information about activities in the field of electronics at Fraunhofer IAF
https://www.iaf.fraunhofer.de/en/networkers.html – More information about collaborating with Fraunhofer IAF
ALMA Band 2 high-frequency receiver
Credit
NOVA/ESO
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