A new experimental set-up for aerosol stability investigations in microgravity conditions

Evaluation of BDS-2 real-time orbit and clock corrections from four IGS analysis centers

The real-time ionospheric data streams are continuously being provided by a number of International GNSS service analysis centers such as Centre National d’Etudes Spatiales (CNES), Chinese Academy of Sciences (CAS), Universitat Politècnica de Catalunya (UPC), and Wuhan University, however, the performance evaluation of these Real-Time Global Ionosphere Map (RT-GIM) products is essential. We assess the quality and consistency of these RT-GIM products from the declining phase of solar cycle 24 (year 2017) to the maximum of solar cycle 25 (year 2024) by comparing with Final GIMs provided by Center for Orbit Determination in Europe (CODE) and Jason-3 altimetry satellite. The results suggest that during the low solar activity periods (2017–2022), all the RT-GIMs perform almost similar. However, the performance of the CNES and CAS RT-GIMs strongly deteriorates as the solar cycle proceeds towards the maximum (2022–2024) with annual RMS values remains between 9 and 7.5 TECU. The external validation vs Jason-3 during this maximum period suggested that the accuracy of the UPC RTGIMs is nearly identical to the final CODE GIMs at typically 4–10 TECU in standard deviation over oceans, while performance degradations are recorded for rest of the RTGIMs exhibiting high standard deviations. Results suggest that the high RMS errors in GIMs from CNES and CAS might be related to the geomagnetic inclination misalignments followed by the map projections as both maps form single peak along geomagnetic equator during high solar activities. In addition, under the presence of a severe G4-class geomagnetic storm, CNES RT-GIMs undergoes severe accuracy degradation across all continents recording a − 20 to − 40 TECU bias offset. Meanwhile, UPC RT-GIM remain the most consistent and stable performer (both, globally and over oceans) that provides accurate global ionospheric information which is promising for their applications in real-time precise GNSS positioning.

The Global Space-based Inter-Calibration System (GSICS) is a new international program to assure the comparability of satellite measurements taken at different times and locations by different instruments operated by different satellite agencies. Sponsored by the World Meteorological Organization and the Coordination Group for Meteorological Satellites, GSICS will intercalibrate the instruments of the international constellation of operational low-earth-orbiting (LEO) and geostationary earth-orbiting (GEO) environmental satellites and tie these to common reference standards. The intercomparability of the observations will result in more accurate measurements for assimilation in numerical weather prediction models, construction of more reliable climate data records, and progress toward achieving the societal goals of the Global Earth Observation System of Systems. GSICS includes globally coordinated activities for prelaunch instrument characterization, onboard routine calibration, sensor intercomparison of near-simultaneous observations of individual scenes or overlapping time series, vicarious calibration using Earth-based or celestial references, and field campaigns. An initial strategy uses high-accuracy satellite instruments, such as the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) and Atmospheric Infrared Sounder (AIRS) and the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT)'s Centre National d'Études Spatiales (CNES) Infrared Atmospheric Sounding Interferometer (IASI), as space-based reference standards for intercalibrating the operational satellite sensors. Examples of initial intercalibration results and future plans are presented. Agencies participating in the program include the Centre National d'Études Spatiales, China Meteorological Administration, EUMETSAT, Japan Meteorological Agency, Korea Meteorological Administration, NASA, National Institute of Standards and Technology, and NOAA.

Ammonia oxidation is an important electrochemical reaction needed in urine purification processes for water reclamation in the International Space Station (ISS). The objective of the microgravity experiment was to compare the ammonia oxidation capabilities of different catalysts at a half cell and in an alkaline fuel cell. Different Pt catalysts were studied, from nanoparticles on carbon supports to platinum nanocubes with preferential crystalline (100) sites. Under microgravity conditions the performance of a fuel cell was diminished by the absence of buoyancy since nitrogen gas was produced, blocking the catalytic sites. The following catalysts were studied: platinum nanocubes (ca. 10nm in diameter), platinum nanocubes on carbon Vulcan and platinum on carbon nanoonion support prepared by the RoDSE method [1]. This research has shown the difference between the performance of the catalysts in an ammonia fuel cell under microgravity and ground experimental conditions, in terms of normalized current densities [1]. In the case of a fuel cell with platinum black at the anode there is a reduction in the produced mass-normalized current densities of around 7.5% between the hypergravity and microgravity experimental episodes. This decrease was shown to be reversed when gravity effects were once again applied to the fuel cell, confirming the direct influence from microgravity on the electrochemical oxidation of ammonia. For the half cell, a decrease in performance of 20-65% over ground-based controls for the electrochemical oxidation of ammonia was found [2,3]. This decrease in current is theorized to be due to the lack of buoyancy driven mixing that occurs in microgravity. In microgravity only diffusional mixing occurs and, therefore, molecules may be unable to reach the nanocatalyst interface at the same rate as on the ground. During the first oxidation peak at ca. 0.7 V vs. Ag QRE, the formation of N2 molecule, during microgravity, conditions creates a stagnant gas-surface interaction that avoids ammonia molecules to reach the Pt surface. This situation leads to a significant peak current decrease compared to the ground experiments. On the other hand, during the second oxidation peak an oxynitride layer is formed at the interface of the electrode without the formation of N2 molecule. This latter peak does not have the effect of microgravity due to the surface chemistry reaction and the oxide adsorbates are no readily desorbed. Therefore, no major differences between the microgravity and ground conditions are observed in such an oxynitride layer region. These findings indicate that significant reductions in electrode performance for ammonia electrooxidation may occur if catalyst design measures are not taken in consideration to mitigate these microgravity effects. This conclusion is applicable specifically to electrochemical processes, but also may be relevant to all process constrained by nanoscale mixing of diffusion limited structures such as thermal catalysts, separation membranes, microbial growth and human cellular functions. For these microgravity experiments, a tailored electrochemical lab was designed and constructed that would handle 2g and 0g gravitational conditions (see Figure 1) [2,3]. References Poventud-Estrada, C. M.; Acevedo, R.; Morales, C.; Betancourt, L.; Diaz, D. C.; Rodriguez III, M. A.; Larios, E.; José-Yacaman, M.; Nicolau, E.; Flynn, M.; and Cabrera, C. R., “Microgravity Effect on Chronoamperometric Ammonia Oxidation at Platinum Nanoparticles Modified Mesoporous Carbon Supports”, Microgravity Science and Technology 2017, 29(5), 381-389. https://doi.org/10.1007/s12217-017-9558-5Acevedo, R.; Poventud-Estrada, C.M; Morales-Navas, C.; Martinez-Rodriguez, R.A.; Ortiz-Quiles, E.; Vidal-Iglesias, F.; Sollá-Gullón, J.; Nicolau, E.; Feliu, J.M.; Echegoyen, L.; Cabrera, C.R., “Chronoamperometric Study of Ammonia Oxidation in a Direct Ammonia Alkaline Fuel Cell under the Influence of Microgravity”, Microgravity Science and Technology 2017, 29(4),253–261. http://dx.doi.org/10.1007/s12217-017-9543-zNicolau, E., Poventud-Estrada, C.M., Arroyo, L., Fonseca, J., Flynn, M., Cabrera, C.R.: Microgravity effects on the electrochemical oxidation of ammonia: A parabolic flight experiment. Electrochim. Acta 2012, 75, 88-93. doi:10.1016/j.electacta.2012.04.079 Figure 1

This work describes the next generation cryogenic sapphire oscillator designed and constructed at the University of Western Australia (UWA), for the PHARAO project developed by the Centre National d'Etudes Spatiales (CNES) and BNM-SYTRE (bureau national de metrologie-systemes de reference temps espace.) The oscillator has now been transported and installed in CNES, Toulouse. It will function as the interrogation oscillator of the prototype and space versions of the PHARAO Cs atomic clock, for all pre-launch ground based tests.

In Thailand, the alteration of weather patterns has resulted in an increase in instances of irregular rainfall, contributing to the occurrence of droughts. The decline of water levels in dams, due to the combined effects of climate change and prolonged droughts, has had a significant impact on agricultural productivity. Drought has a profound effect on the terrestrial biosphere and the atmospheric water cycle and can also contribute to air pollution. Researchers have found a strong correlation between air pollution and drought severity. In response to this pressing issue, the Excellence Center of Space Technology and Research (ECSTAR) at King Mongkut’s Institute of Technology Ladkrabang has joined forces with TeroSpace company to launch an initiative aimed at promoting sustainable growth in Chiang Rai, a province in Thailand known for its rich biodiversity. ECSTAR and TeroSpace’s partnership on the sustainable growth initiative in Thailand’s Chiang Rai province focuses on expanding their collaboration to include international organizations such as the Centre National d’Etudes Spatiales (CNES), which will provide access to satellite imagery and climate and weather information to improve decision-making in various areas of development. CNES is a French organization in charge of space-related activities in France. The collaboration between France and Thailand for this project, in the context of the France-Thailand Year of Innovation 2023, will be crucial for the successful initiation and execution of this research project. The project aims to explore the relationship between air pollution and climate change through the deployment of air quality monitoring devices in designated locations, connected to a global data-sharing network. The results of this research will be valuable to policymakers as they consider the interplay between air pollution and climate change and make efforts to address these challenges.

Precise real-time kinematic (RTK) Global Navigation Satellite System (GNSS) positioning requires fixing integer ambiguities after a short initialization time. Originally, it was assumed that it was only possible at a relatively short distance from a reference station (<10 km), because otherwise the atmospheric effects prevent effective ambiguity fixing. Nowadays, through the use of VRS, MAC, or FKP corrections, the distances to the closest reference station have been increased to around 35 km. However, the baselines resolved in real time are not as far as in the case of static positioning. Further extension of the baseline requires the use of an ionosphere-weighted model with ionospheric delay corrections available in real time. This solution is now possible thanks to the Radio Technical Commission for Maritime (RTCM) stream of SSR corrections from, for example, Centre National d’Études Spatiales (CNES), the first analysis center to provide it in the context of the International GNSS Service. Then, ionospheric delays are treated as pseudo-observations that have a priori values from the CLK RTCM stream. Additionally, satellite orbit and clock errors are properly considered using space-state representation (SSR) real-time radial, along-track, and cross-track corrections. The following paper presents the initial results of such RTK positioning. Measurements were performed in various field conditions reflecting realistic scenarios that could have been experienced by actual RTK users. We have shown that the assumed methodology was suitable for single-epoch RTK positioning with up to 82 km baseline in solar minimum (30 March 2019) mid and high latitude (Olsztyn, Poland) conditions. We also confirmed that it is possible to obtain a rover position at the level of a few centimeters of precision. Finally, the possibility of using other newer experimental IGS RT Global Ionospheric Maps (GIMs), from Chinese Academy of Sciences (CAS) and Universitat Politècnica de Catalunya (UPC) among CNES, is discussed in terms of their recent performance in the ionospheric delay domain.

Testing the weak equivalence principle to a precision of 10−15 requires a quantity of data that give enough confidence on the final result: ideally, the longer the measurement the better the rejection of the statistical noise. The science sessions had a duration of 120 orbits maximum and were regularly repeated and spaced out to accommodate operational constraints but also in order to repeat the experiment in different conditions and to allow time to calibrate the instrument. Several science sessions were performed over the 2.5 years duration of the experiment. This paper aims to describe how the data have been produced on the basis of a mission scenario and a data flow process, driven by a tradeoff between the science objectives and the operational constraints. The mission was led by the Centre National d’Etudes Spatiales (CNES) which provided the satellite, the launch and the ground operations. The ground segment was distributed between CNES and Office National d’Etudes et de Recherches Aérospatiales (ONERA). CNES provided the raw data through the Centre d’Expertise de Compensation de Traînée (CECT: drag-free expertise centre). The science was led by the Observatoire de la Côte d’Azur (OCA) and ONERA was in charge of the data process. The latter also provided the instrument and the Science Mission Centre of MICROSCOPE (CMSM).

The PPP-B2b service of BeiDou-3 enables real-time precise point positioning (RT-PPP) through correction information contained in B2b signals, circumventing the reliance on ground-based network infrastructures. This study comprehensively evaluates the accuracy of PPP-B2b correction parameters and their impact on positioning and tropospheric zenith total delay (ZTD) estimation. The PPP-B2b DCB products exhibit good consistency with the Chinese Academy of Sciences (CAS) reference, with average differences below 1.2 ns and standard deviations within 0.11 ns, indicating comparable performance to CAS products. For BDS-3 satellites, PPP-B2b achieves a radial orbit accuracy of 0.07 m and a clock standard deviation of 0.17 ns, outperforming the Centre National d’Études Spatiales (CNES) real-time products in both aspects. For GPS satellites, the corresponding accuracies are 0.06 m and 0.20 ns. Kinematic PPP experiments using combined GPS and BDS-3 observations yield horizontal and vertical accuracies of 4.3 cm and 2.8 cm, respectively, comparable to CNES results, while the BDS-3-only solution performs better than CNES but is still slightly inferior to the CODE. The ZTD estimation accuracy reaches 1.8 cm for GPS+BDS-3 combinations and 2.3 cm for BDS-3-only cases. Overall, PPP-B2b delivers centimeter-level performance in real-time positioning and ZTD estimation, demonstrating strong potential as an independent, space-based precise service, though further improvement is required for GPS-only applications.

The history of the ERS–2 satellite is closely linked with that of its predecessor, ERS-1. The first one was launched on July 17, 1991, followed by ERS-2 on April 21, 1995. Both satellites significantly exceeded their original design life of three years, contributing extensively to various scientific and environmental applications during their operational periods. This study focuses on the ERS-2 satellite, whose mission officially ended on September 5, 2011. The final image from ERS-2 was received on July 4, 2011. Subsequently, after executing 66 deorbiting maneuvers, the satellite’s altitude was reduced from 780 km to 573 km to facilitate natural orbital decay due to atmospheric drag. Approximately thirteen years later, on February 21, 2024, ERS-2 completed its atmospheric re-entry over the North Pacific Ocean, between Alaska and Hawaii, at the estimated coordinates 37°24’00.0”N and 151°54’00.0”W, at 18:17 CET (17:17 UTC). The objective of this paper is to evaluate the probability of Earth impact by surviving fragments and to estimate the casualty area resulting from debris. Our analysis assumes that all satellite systems were deactivated, batteries disconnected, fuel purged, and the wind scatterometer folded. Utilizing this baseline and additional data published by ESA in Bulletin83 (1995), we reconstructed the ERS-2 satellite model to perform re-entry simulations using three representative tools: Debris Assessment Software (DAS) developed by National Aeronautics and Space Administration (NASA), Debris Risk Assessment and Mitigation Analysis (DRAMA) developed by European Space Agency (ESA) and DEBRISK developed by Centre National d’Etudes Spatiales (CNES).

The Soil Moisture and Ocean Salinity (SMOS) satellite is a 2D interferometer in L-band (1.4 GHz). Over land, it enables to probe the earth surface emissivity related to soil moisture in the first centimeters of the soil, with an aimed accuracy better than 4m³.m^-3 and an average spatial resolution of 40km. The European Space Agency's (ESA) ground segment provides half-orbit soil moisture products at level 2. The Centre National d'Etudes Spatiales (CNES) in France has developed the CATDS (Centre Aval de Traitement des Données SMOS) ground segment in order to produce global maps, known as level 3 and 4 products. Over land, the algorithm is based on the level 2 soil moisture ESA's prototype. The major enhancement of the CATDS concerns the use of multi-orbit retrieval. The level 3 Soil moisture (SM) products are global maps of soil moisture, and other geophysical products (vegetation optical thickness, albedo, soil dielectric constant or surface temperature). For a particular point, the revisit time is between 1 and 3 days, and the entire Earth's surface is covered by SMOS field of view in 3 days. Level 3 SM products are available over different time periods. First, a 1 day global product is generated for each day. Then, 1 day global maps are aggregated in 3-day global products, 10- day and monthly products.

TOPEX/POSEIDON is a satellite mission that will use a radar altimeter system to measure sea level, which will reveal ocean topography and enable study of the circulation of the world's oceans. The measurement will also be useful for the study of ocean tides and marine geodesy and geophysics. Figure 1 is an artist's rendition of the TOPEX/POSEIDON satellite flying above the Earth. The mission is jointly conducted by the National Aeronautics and Space Administration (NASA) and the French space agency, Centre National d'Etudes Spatiales (CNES). Current plans call for launch of the satellite by an Ariane launch vehicle in the summer of 1992. The primary mission will last for 3 years, with the possibility of extending the mission 2 more years. The mission has been coordinated with a number of international oceanographic and meteorological programs, including the World Ocean Circulation Experiment (WOCE) and the Tropical Ocean and Global Atmosphere Programme (TOGA), both of which are sponsored by the World Climate Research Programme (WCRP). The observations of TOPEX/POSEIDON are timed to provide a global perspective for interpreting the in situ measurements collected by these programs, which will in turn be combined with satellite observations to achieve a global, four‐dimensional description of the circulation of the world's oceans. Born et al. [1984] gives the background for the early phase of the mission's development. This article gives an updated overview of the mission as it is currently configured for launch in the next year.

The Large Ultraviolet / Optical / Infrared Surveyor (LUVOIR) is one of four large mission concepts being study by NASA in preparation for the 2020 Decadal Survey in Astronomy and Astrophysics. Over the past three and a half years, the LUVOIR Science and Technology Definition Team (STDT) and Study Office at NASA’s Goddard Space Flight Center have developed a broad, compelling science case for LUVOIR, and detailed engineering point designs to achieve it. In this paper, we provide an overview of the two LUVOIR concepts: LUVOIR-A, a 15-m segmented, obscured aperture observatory, and LUVOIR-B, an 8-m segmented, unobscured aperture observatory. Both versions of LUVOIR cover a broad spectral range between 100 nm and 2.5 &mu;m with a suite of imagers and spectrographs, including the High Definition Imager (HDI), the LUVOIR Ultraviolet Multi-object Spectrograph (LUMOS), and the Extreme Coronagraph for Living Planetary Systems (ECLIPS). LUVOIR-A will carry an additional fourth instrument, Pollux, a high-resolution UV spectropolarimeter being studied by the Centre National d’Etudes Spatiales (CNES). Both versions of LUVOIR are also designed to be serviceable and upgradeable. We will also provide a summary of the LUVOIR technology development program, which identifies critical enabling technologies, enhancing technologies, and a development plan to mature those technologies to TRL 6.

At the end of the century, Europe will realise rendez-vous between satellites in space. Basic studies have already started at CNES (Centre National d'Etudes Spatiales). A breadboard model of a radar which provides the necessary information during an automatic docking manoeuver is presented. This FM-CW, Ka band radar will be located on the arm extremity of a robotised hunting satellite. The main feature of this instrument is to measure, relative distance, relative speed and angular position at very short distances (inferior to one metre).

3D PLUS has developped in the framework of R&D activities an advanced CMOS camera for Space applications. The Centre National d’Etudes Spatiales (CNES), also called French space agency, is leading the developement of this camera, see Figure 1. This instrument has been integrated using the 3D PLUS technology [1] in order to be as compact as possible. Particular attention has been paid to ensure a good radiation tolerance to cover a wide range of scientific applications such as planetology, but also platform or launcher monitoring and star trackers