Iridium has developed an Application-Specific Integrated Circuit (ASIC) that is more readily incorporated into receiver designs by lowering costs and decreasing integration complexity without sacrificing performance. As an all-in-one receiver design, the Iridium PNT ASIC also significantly reduces the size of PNT UE, making it more suitable for a range of new applications when GNSS is unavailable.

The 8mm x 8mm package enables up to two independently configurable pulse-per-second (PPS) and positioning outputs that utilize the built-in Iridium PNT receiver with an optional interconnected external GPS/GNSS receiver. In the latter architecture, it supports automatic, seamless failover of PPS control between Iridium PNT and GPS/GNSS as signal conditions warrant. Furthermore, it allows for continuous monitoring and comparison of the Iridium PNT and GPS/GNSS PVT solutions against each other, aiding anomaly detection, with the option to use an external PPS input as an additional timing reference to help resolve ambiguity. This flexibility presents opportunities to design a standalone receiver offering only Iridium PNT or to create a highly resilient dual-mode device with Iridium PNT and GPS/GNSS signals.

This presentation will include details about the Iridium PNT ASIC that will be of interest to users and integrators alike and provide not only results from the lab but also real-world performance data from actual use cases on land and at sea.

NOTE TO ENC PROGRAM COMMITTEE: This abstract is being submitted under topic 4.6 Receiver Trends and New Technologies. However, at your discretion you may choose to associate it with 3.2 Performance & Anomaly Detection, 5.1 Trends in Navigation Technology & System Design, or 5.2 LEO PNT

The Passive Reflectometry and Dosimetry (PRETTY) spacecraft, now part of ESA's OPS-SAT SpaceLab fleet, successfully conducted measurements to determine the properties of the Earth's surface using passive reflectometry of Global Navigation Satellite System (GNSS) signals to support climate change research. These measurements require a precise attitude determination and control system (ADCS) to direct the spacecraft and its antennas to the reflection point. The ADCS utilises the on-board GNSS receiver to reliably determine its own position, but disturbances where observed in the navigation data: The onboard receiver intermittently loses its position solution, and subsequently reports another valid solution which is obviously offset from the true location of the spacecraft. However, since the solution is flagged as valid, the flight software can not reliably determine the situation, and revert automatically to a robust backup, such as a Two-Line Element (TLE)-based propagator, for attitude control.
This paper analyses these GNSS disturbances and their effect on the spacecraft's ADCS. First, the observed signal anomalies are characterised by their position solution and time of occurence. The core analysis then focuses on the cascade effect of how a wrong position drifts the estimated attitude, and how the control system attempts to compensate for this false estimation. This leads to an increased control effort, causing the spacecraft to deviate from its intended pointing profile. Finally, the paper discusses practical risk mitigation strategies, emphasising the importance of implementing fail-safe logic so that the ADCS can seamlessly transition to a TLE-based propagation mode. The results highlight a critical vulnerability in integrated GNSS/ADCS designs, and the discussed mitigation measures can help other missions effectively improve the robustness of their systems in the presence of GNSS interference.

When planetary rovers land on extraterrestrial surfaces, it is not taken for granted that the terrain is known and neither is there a Global Navigation Satellite System GNSS. This is an important issue if not one but more rovers collaborate on the same area. On the other hand, two or more rovers can explore a much wider area in the same time and by good fusion of results gain a more complete impression. And as long as the rovers operate close to the landing site, sensors on the lander can further enhance the output.
This scenario has been put into practice at the German Aerospace Center DLR with two very different mobile robots, the Lightweight Rover Unit LRU and the Space Cave explOration UniT SCOUT, and a stationary Road-Side-Unit RSU. During one of the measurement runs, the systems were expanded with an Ultra-Wide Band UWB localization network to provide a second external tracking of the mobile robots.
Operating these systems together, but independently from each other, already results in a good map of the site more rapidly than would be done by just one system. Fusion of the individual measurements in a second step results in a better map of the site as would have been measured by just one system. Therefore, an important part of the setup, and of this publication, is the common network and data exchange between the systems.
The Robot Operating System 2 ROS2 is the middleware for LRU, SCOUT and RSU. The three systems further are in the same network that also has a Network Time Protocol NTP for time synchronization. This permits an online data fusion. How to further enhance the outcome in post processing is shown with the additional UWB distance measurement. An important advantage is that the systems need not know each other prior network setup as long as they run the same ROS version or provide bridges for compatibility over different versions. This makes the advantages of a heterogeneous team of robots (complementary sensors, different mobility capabilities, co-working, etc.) as easy to put into practice as a team of homogeneous systems.
The activity shows that collaborative exploration and Simultaneous Localization And Mapping SLAM of an unknown off-road terrain as expected for example on the Moon is possible with rovers and stationary sensors using relatively simple systems and setup and without excessively large computational power. The text also shows the pitfalls and limitations of the systems and gives hints how to overcome them. This can be of good inspiration for future exploration of the Solar System with heterogeneous robotic systems as is foreseeable with the current development in national and international Moon programs but not yet reality. The setup can likewise be applied in terrestrial situations where human beings would be set to risk, e.g. collapsed buildings or areas with toxic atmosphere, or where common solutions based on GNSS and a priori knowledge of the terrain are not possible.

In the recent past, a global interest in Moon exploration has steadily increased. This fact is testified by the significant number of missions planned for the upcoming decade targeting the Moon surface.
The availability of a specialized navigation system that can provide Positioning, Navigation, and Timing (PNT) support to users both in orbit and on the lunar surface is of paramount importance to facilitate an enduring lunar colonization. Huge efforts have been jointly devoted by the European, the United States, and the Japanese Space Agencies to the definition of the so-called LunaNet framework, an interoperable service network facilitating communication, networking, and navigation on a lunar scale. Among the identified LunaNet services, the Lunar Augmented Navigation Service (LANS) relies on the broadcast of a one-way ranging signal, called Augmented Forward Signal (AFS). The LANS is conceptually similar to Earth-based GNSS but adapted for lunar operational requirements. One of these adaptations is the allocation of the AFS in the S-band of the Radio Frequency (RF) spectrum.
The DEMOS-1 activity aimed at assessing the capability of a fixed lunar surface station, such as ESA’s NovaMoon mission, to augment the PNT service delivered by the planned lunar-orbiting satellite constellations, either by transmitting a ranging signal compatible with AFS standard or by acting as a reference station to support monitoring and differential positioning. This effort resulted in the design and implementation of an Elegant Breadboard (EBB) used for controlled laboratory demonstrations.
The EBB is equipped with a prototype receiver capable of acquiring and tracking the RF signals defined by the first version of the AFS Interface Control Document (ICD) and the station beacon able to generate a RF signal equivalent to the LunaNet AFS, with possibility to synchronize to the LCNS system time. Finally, an on-board computer is mounted to compute the station position, the differential corrections, and to control to station beacon.
An end-to-end laboratory test environment was completed by the development of the Ground Support Equipment (GSE). This unit mounts the custom RF Constellation Simulator (RFCS) developed to generate RF signals implementing the first Interface Control Document (ICD) LunaNet and AFS specifications. To emulate a LunaNet LANS user, the GSE mounts the prototype LunaNet receiver and an on-board computer to fulfill the navigation capabilities, exploiting the augmentation information ensured by the Moon Station EBB.
With this setup deployed in ESA’s Navigation Laboratory at ESTEC, simulations under representative lunar conditions were conducted to assess the navigation performance of the GSE user receiver. The analysis progressed from using the LANS signals alone, then the augmentation granted by the EBB is considered, either by integrating the additional station signal or by applying the generated differential corrections. Additionally, the improvements brought by the exploitation of altitude information through a Digital Elevation Model (DEM) are investigated as well. The results demonstrate a clear improvement in positioning accuracy across these steps, marking an important advancement toward delivering augmented PNT services for future lunar surface operations within the LunaNet framework.

Atomic clocks are fundamental to Global Navigation Satellite Systems (GNSS), ensuring precise positioning and timing worldwide. I will present recent results from two projects that advance clock technologies for next‑generation GNSS.

The first project investigates rubidium microwave clocks in microgravity. Using optical dipole traps and a novel scheme to cancel differential light shifts via time‑averaged potentials, we demonstrate a novel approach for microwave frequency references. Preliminary experiments with trapped rubidium atoms highlight the potential for improved space‑qualified clocks.

The second project focuses on compact optical lattice clocks with ytterbium and strontium. We developed chip‑based microstructured ovens and integrated optical elements that enable efficient magneto‑optical trapping with a single incident laser beam. Combined with additively manufactured miniature vacuum chambers, these setups achieve high atom loading rates in volumes below 750 ml.

Together, these advances point toward robust rubidium clocks and compact optical lattice clocks for future GNSS applications.