The Space Geodesy Project and Radio Frequency Interference Characterization and Mitigation

The Space Geodesy Project (SGP) development by NASA is an effort to co-locate the four international geodetic techniques Satellite Laser Ranging (SLR) and Lunar Laser Ranging (LLR), Very Long Baseline Interferometry (VLBI), Global Navigation Satellite System (GNSS), and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) into one tightly referenced campus and coordinated reference frame analysis. The SGP requirement locates these stations within a small area to maintain line-of-sight and frequent automated survey known as the vector tie system. This causes a direct conflict with the new broadband VLBI technique. Broadband means 2-14 GHz, and RFI susceptibility at -80 dBW or higher due to sensitive RF components in the front end of the radio receiver

Comparison of the frequency estimation of the DORIS/Jason2 oscillator thanks to the onboard DIODE and Time Transfer by Laser Link experiment

International audienceThe main applications for DORIS are precise orbit determination, and precise Geodesy. Onboard Jason-2 for instance, the DORIS tracking component is the French contribution to the precise orbit determination capability, a key capability for altimetry product scientific result accuracy. T2L2 is a time transfer technique based on the propagation of light pulses for synchronization between two clocks. Hosting T2L2 on-board Jason-2 was to allow for very fine DORIS USO (Ultra-Stable Oscillator) frequency monitoring, and for this purpose T2L2 was connected to the DORIS USO. Thanks to the continuous tracking of T2L2/Jason-2 by the Laser Ranging network it is possible to monitor the USO for several days, weeks, and even much longer, and thus to also compare with the DIODE (the DORIS on-board orbit determination software) frequency bias estimates. The DORIS USO frequency biases estimate comparison between two independent systems, T2L2 and DIODE, can be of benefit to both, allowing the accuracies of both systems to be better understood, and for improvements to be made to both systems. Such comparison is the central topic of the present paper. T2L2 monitors the DORIS on-board USO frequency with an accuracy of much better than 10−12 which is the specification for the Doppler instrumentation.The paper investigates the limits of the DORIS-DIODE frequency bias estimates using T2L2, showing that USO frequency compliance accuracy of 10−12 has been reached

CFOSAT: Products Reprocessing and Contributions in Oceanography

International audienceSince 2018, for the first time, space measurements of colocated wind vectors and wave spectral characteristics are available thanks to the French/Chinese CFOSAT mission, which carries a wind scatterometer (SCAT) and a wave scatterometer (SWIM). Four years after its launch, CFOSAT data processing has been improved to reach a high level quality, leading to a reprocessing of the whole mission dataset. This paper focuses on the CFOSAT SWIM data reprocessing, the product performance, now homogeneous over mission lifetime, the complementarity with SAR observations and some scientific contributions to oceanography

Evolutions and Improvements in CFOSAT SWIM Products

International audienceThe Chinese-French oceanography satellite, CFOSAT, was launched on October 2018. Two Ku-band scatterometers are on-board: SCAT for the wind observation and SWIM for the wave observation. After a first phase mainly dedicated to validation and identification of improvement possibilities, the ground processing and products generated were upgraded. This paper presents the main evolutions implemented and their positive impacts on the SWIM data quality

The Swim Instrument, Towards the Launch

International audienceThe wave scatterometer, SWIM, will be on-board the Chinese French oceanographic mission, CFOSAT. It will complete the Chinese wind scatterometer, SCAT. They will provide the scientific community with joint wind and wave measurements for the very first time. The launch is now coming soon: autumn 2018. SWIM is a Ku-band real-aperture radar with 6 rotating fan-beams pointing near nadir. The main characteristics and performance of the instrument measured during the Satellite Integration Campaign, products and ground segment development are presented in this paper, as well as predicted performances estimated from simulations

Ultrafast light targeting for high-throughput precise control of neuronal networks

Current holographic approaches for neuronal stimulation have limitations in their temporal resolution and the number of targeted neurons. Here, the authors demonstrate an approach for ultra-fast holographic light targeting which, combined with optogenetics, enables sub-millisecond control of sequential neuronal activation and high throughput simultaneous multicell illumination

CAL/VAL phase for the SWIM instrument onboard CFOSAT

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First results on wave spectral parameters from the CFOSAT satellite

International audienceCFOSAT is a new satellite mission launched on October 29th, 2018. It is developed since 2006 thanks to a fruitful Chinese-French cooperation involving the French Space Agency CNES, the Chinese agencies CNSA and NSOAS, and scientific support from various research laboratories in France and China.CFOSAT will provide for the first time colocated and global observations on the surface ocean wind vector, and ocean wave spectral parameters (wave spectra and associated parameters) from a combination of two Ku-Band radar instruments (SWIM and SCAT) working in altimeter and wave spectrometer modes (SWIM) and wind scatterometer mode (SCAT). The CFOSAT products will offer the opportunity to develop new studies from global observations, such as joint analysis of space evolution of wind and waves, detailed analysis of the spectral properties of the wave field (in particular its directionality) and relationship between long waves (measured by SWIM) and short wave properties (indirect information from the normalized radar cross-section). The data will also be used in data assimilation schemes of wave and atmospheric numerical models (through assimilation) in order to improve wave and atmospheric forecast. The information on peak wavenumber, wave direction, directional spread for several wave spectrum partitions, will also be of great interest to study wave/current interactions and to feed the coastal studies with sea state boundary conditions.During this conference, less than six months after the launch, the first results on the products generated in near real-time by the CNES mission center will be presented. First the data processing principles of the SWIM data and the main products will be recalled. Then, a first assessment of the normalized radar cross-section at near-nadir incidence and of wave products (significant wave height, dominant direction and dominant wave length, for the whole spectra and separated by wave partitions) will be presented. This first assessment of the SWIM products relies on the work of a CAL/VAL team which carries out comparisons between CFOSAT data, satellite altimeter products, wave forecast model products (ECWAM, MFWAM, WW3), in situ data, and other satellite data (such a Sentinel-1 wave mode data)

Socio-politically polarized contexts, urban mobilization and the environmental movement: a comparative study of two campaigns of protest in Northern Ireland

This article uses a structural approach to the investigation of the continuity and discontinuity between 'old' urban and 'new' environmental protest, opening further space for analysis of the relationship between different mobilizations in Northern Ireland. In particular, I suggest that the 'novelty' and strength of social movements' challenges can be assessed in terms of their capacity to promote participation and cooperation between the opposite poles of established cleavages, especially when one engages in the analysis of socio-politically polarized contexts. In this article I focus on two mobilizations. On the one hand, I show that the first Westlink protest of the 1970s was not the product of an integrated social movement but, rather, of a heterogeneous and instrumental coalition of urban and political actors which gained no support from formal environmental organizations and soon split along the national-religious divide. On the other hand, I show that the current Westlink campaign is the product of a cohesive network, which cuts across the many socio-political cleavages of Northern Ireland, linking together local, urban and community groups, conservation and environmental organizations, associations, universities, political actors and parties, of opposing national-religious identity. I then take these two patterns of mobilization as a dependent variable and explain them by drawing on theories of resource mobilization, new social movements, framing and political opportunity structure. Copyright Joint Editors and Blackwell Publishing Ltd 2003.