A generic 2048‐point FFT acquisition architecture is proposed to address L1 civil signals from all four GNSS constellations. After emphasizing hardware design criteria and their resulting design limitations, software compensation approaches are compared. A detailed validation methodology, involving a successive 1000‐step Monte‐Carlo study, was defined to optimally configure the acquisition channel, with new metrics to establish formal signal detection. The integration thereof results in a novel, minimalistic, yet generic, acquisition channel implementation, as well as a thorough validation method. Execution time of one acquisition iteration is approximately 5 ms, in line with VHDL simulations and foreseen channel management overhead. Coarse/fine search increments and thresholds are based on extensive experimentation. A 41 dB‐Hz acquisition sensitivity threshold was established to achieve >95 % detection rates for 1 ms integrations, while 15 ms non‐coherent integrations are required for signal strengths down to 37 dB‐Hz. These thresholds account for known implementation losses. Copyright © 2015 Institute of Navigation

This paper presents a universal GNSS receiver channel capable of tracking any civil GNSS signal. This fundamentally differs from dedicated channels, each customized for a given signal. A mobile device could integrate fewer universal channels to harvest all available signals. This would allow securing signal availability, while minimizing power consumption and chip size, thus maximizing battery lifetime. In fact, the universal channel allows sequential acquisition and tracking of any chipping rate, carrier frequency, FDMA channel, modulation, or constellation, and is totally configurable (any integration time, any discriminator, etc.). It can switch from one signal to another in 1.07 ms, making it possible for the receiver to rapidly adapt to its sensed environment. All this would consume 3.5 mW/channel in an ASIC implementation, i.e., with a slight overhead compared to the original GPS L1 C/A dedicated channel from which it was derived. After extensive surveys on GNSS signals and tracking channels, this paper details the implementation strategies that led to the proposed universal channel architecture. Validation is achieved using GNSS signals issued from different constellations, frequency bands, modulations and spreading code schemes. A discussion on acquisition approaches and conclusive remarks follow, which open up a new signal selection challenge, rather than satellite selection.

Recent measurements of the reflection of the surface of a lava world provides an unprecedented opportunity to investigate different stages of rocky planet evolution. The spectral features of the surfaces of rocky exoplanets give insights into their evolution and inner workings. However, no database exists yet that contains spectral reflectivity and emission of a wide range of potential volcanic exoplanet surface materials. Here we first synthesized 16 possible exoplanet surfaces, spanning a wide range of chemical compositions based on potential mantle material of volcanic exoplanets guided by the metallicity of different host stars. Then we measured their infrared reflection spectrum (2.5–28 μm), from which we can obtained their emission spectra, and established the link between the composition and a strong spectral feature at 8 μm, the Christiansen feature (CF). Our analysis suggests a new multi-component composition relationship with the CF, as well as a correlation with the silica content of the exoplanet mantle. We also report the mineralogies of these materials, as possibilities for volcanic worlds. This database is a tool to aid in the interpretation of future spectra of volcanic and lava worlds that will be collected by the James Webb Space Telescope and other missions.

This paper presents observations on the WAAS L1 and L5 signals quality and their impact on the robustness of the navigation solution by quantifying the contributions of each broadcasted differential correction. This work is undertaken with the intent of defining performance benefits of L5 by dual frequency WAAS users and is to provide useful material for Minimum Operational Performance Standard (MOPS) development. In this perspective, a study of the WAAS signal characteristics is first carried out. The information gathered is then used to compare various GPS solutions in terms of frequency diversity, satellite diversity, pseudorange noise and different signal corrections and their impacts. These solutions are compared against a reference standalone GPS solution. All statistics are computed with respect to a post-processed Novatel Waypoint Real-Time Kinematics (RTK) GPS L1/L2 semi-codeless static solution, considered as the reference. A discussion on some simplifications with respect to specifications (i.e. MOPS) that could be considered by receiver manufacturers closes the paper. It is confirmed that the current WAAS navigation message definition is the same on both the L1 and L5 frequencies, the latter further being Manchester coded, thus avoiding data ambiguity. The +5 dB SNR on L5 has minor impacts in terms of reliability and continuous availability in the presented scenarios, but would become especially beneficial in hostile environments, despite a greater number of pulsed interferers. Another demonstration is that the WAAS message varies slightly from one WAAS satellite to another, even if corrections are generated centrally. Finally, it is observed that WAAS and GPS signals pseudorange noise are comparable on a "per frequency" basis.

No abstract