With the renewed interest in lunar surface exploration, the European Space Agency envisions to stimulate the creation of lunar communications and navigation services (LCNS) to enable, among others, autonomous navigation capabilities for lunar rovers. As the number of satellites foreseen in such a service is much smaller compared to Earth-based global navigation satellite systems, different complementary technologies are pursued to improve the attainable navigation accuracy for lunar rovers. One way to improve the position accuracy provided by the LCNS satellites is to constrain their vertical position using a high resolution digital elevation model (DEM). This article presents the results of a variance covariance analysis of an extended Kalman filter implementation in which the LCNS ranging measurements are used together with the altitude provided by a DEM from the Lunar Orbiter Laser Altimeter instrument of the Lunar Reconnaissance Orbiter. Assuming a realistic orbit determination and time synchronization accuracy of the LCNS satellites, the usage of a navigation-grade inertial measurement unit and an oven-controlled crystal oscillator, a 3-sigma position accuracy of less than 10 m can be obtained. Furthermore, the availability is substantially improved as the DEM-aided solution enables a position solution in case of only 3 visible satellites.

The idea of multichannel tracking is generally found in the Global Navigation Satellite System (GNSS) literature with a wideband approach. We further developed the concept to separately process two narrowband channels that are later combined in a dedicated delay-locked loop (DLL) in a virtual wideband fashion. To suit prospect evolution of positioning, navigation, and timing (PNT) technologies and GNSSs, we generalized the so-called meta-signal construction to the combination of components transmitted over the same bandwidth, thus expanding the range of candidate multichannel components and fostering efficient bandwidth exploitation and increased resiliency to harsh Doppler. These improvements are sustained by additional complexity at the receiver, whose robustness must be carefully assessed. The resulting architecture performance in presence of multipath and tracking noise is therefore characterized under the challenging conditions of modern GNSSs, focusing on a low earth orbit (LEO) PNT scenario. The technique can successfully bear the representative Doppler profiles and $C/N_{0}$ levels of the addressed scenarios achieving a large estimation noise reduction, even under challenging multipath conditions.

With the renewed interest for lunar surface exploration, the European Space Agency envisions to stimulate the creation of lunar communications and navigation services (LCNS) to enable, among others, autonomous navigation capabilities for lunar rovers. As the number of satellites foreseen in such a service is much smaller compared to Earth based global navigation satellite systems (GNSS), different complementary technologies are pursued to improve the attainable navigation accuracy for lunar rovers. One way to improve the position accuracy provided by the LCNS satellites is to constrain the vertical position using a high resolution digital elevation model (DEM). This article presents the results of a variance covariance analysis of an extended Kalman filter (EKF) implementation in which the LCNS ranging measurements are used together with DEM from the LRO LOLA instrument. Assuming a realistic orbit determination and time synchronization (ODTS) accuracy of the LCNS satellites, the usage of a navigation grade IMU and an oven controlled crystal oscillator (OCXO), a 3-sigma position accuracy of less than 10 meters can be obtained. Furthermore, the availability is substantially improved as the DEM aided solution enables a position solution in case of only 3 visible satellites.