Observing Polar Regions from Space: Comparison between Highly Elliptical Orbit and Medium Earth Orbit Constellations

AbstractContinuous observation of polar regions from space remains an important unsolved technical challenge of great interest for the international meteorological community. This capacity would allow achieving global continuous coverage once combined with the geostationary (GEO) satellite network. From a practical point of view, continuous coverage of polar regions with a small number of spacecraft can be obtained from a constellation of satellites either in highly elliptical orbits (HEO) or in medium Earth orbits (MEO). The study compares HEO and MEO satellite constellations for their capacity to provide continuous imaging of polar regions as function of the viewing zenith angle (VZA) and evaluates the corresponding latitude limits that ensure sufficient overlap with GEO imagery. Earlier studies assumed the latitude boundary of 60° and the VZA range 70°–85° depending on the space mission focus: meteorological purposes or communications. From the detailed analysis of meteorological retrieval requirements, this study suggests that the overlap of the GEO and polar observing systems (HEO or MEO) should occur down to the latitude band 45°–50° with a maximum VZA ranging between 60° and 64°. This coverage requirement can be met with two sets of three-satellite HEO constellations (one for each polar area) or a six-satellite MEO constellation. The 12-h Molniya and 14-, 15-, and 16-h HEO systems have been analyzed and determined to meet these revised requirements. The study demonstrates that the six-satellite 24-h MEO system can provide a suitable solution, which is also beneficial from the point of view of ionizing radiation and image acquisition geometry. Among the HEO systems, the 16-h HEO has some advantages relative to other HEO systems from the point of view of spatial coverage and space radiation.

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A New Tool for Airborne Gravimetry Survey Simulation

Geosciences ◽

10.3390/geosciences8080292 ◽

2018 ◽

Vol 8 (8) ◽

pp. 292 ◽

Cited By ~ 3

Author(s):

Daniele Sampietro ◽

Ahmed Mansi ◽

Martina Capponi

Keyword(s):

Oil And Gas ◽

Survey Design ◽

Cost Effective ◽

Point Of View ◽

Global Navigation Satellite Systems ◽

Polar Regions ◽

Airborne Gravimetry ◽

Satellite Systems ◽

Observation Noise ◽

Airborne Survey

Airborne gravimetry represents nowadays probably the most efficient technique to collect gravity observations close to the Earth’s surface. In the 1990s, thanks to the development of the Global Navigation Satellite Systems (GNSS), which has made accurate navigational data available, this technique started to spread worldwide because of its capability to provide measurements in a fast and cost-effective way. Differently from other techniques such as shipborne gravimetry, it has the advantage to provide gravity measurements also in challenging environments which can be difficult to access otherwise, like mountainous areas, rain forests and polar regions. For such reasons, airborne gravimetry is used for various applications related to the regional gravity field modelling: from the computation of high accurate local geoid for geodetic applications to geophysical ones, specifically related to oil and gas exploration activities or more in general for regional geological studies. Depending on the different kinds of application and the final required accuracy, the definition of the main characteristics of the airborne survey, e.g., the planar distance between consecutive flight tracks, the aircraft velocity, etc., can be a difficult task. In this work, we present a new software package, which would help in properly accomplishing the survey design task. Basically, the developed software solution allows for generating a realistic (from the observation noise point of view) gravimetric signal, and, after that, to predict the accuracy and spatial resolution of the final retrievable gravimetric field, in terms of gravity disturbances, given the flight main characteristics. The proposed procedure is suited for airborne survey planning in order to be able to optimize the design of the survey according to the required final accuracy. With the aim to evaluate the influence of the various survey parameters on the expected accuracy of the airborne survey, different numerical tests have been performed on simulated and real datasets. For instance, it has been shown that if the observation noise is not properly modeled in the data filtering step, the survey results degrade about 25%, while not acquiring control lines during the survey will basically reduce the final accuracy by a factor of two.

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Spatial and Temporal Sampling of Polar Regions from Two-Satellite System on Molniya Orbit

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-10-05013.1 ◽

2011 ◽

Vol 28 (8) ◽

pp. 977-992 ◽

Cited By ~ 15

Author(s):

Alexander P. Trishchenko ◽

Louis Garand

Keyword(s):

Temporal Resolution ◽

Arctic Region ◽

Satellite System ◽

Elliptical Orbit ◽

High Temporal Resolution ◽

Polar Regions ◽

Temporal Sampling ◽

Continuous Coverage ◽

Depth Analysis

Abstract There has been a significant increase of interest in the building of a comprehensive Arctic observing system in recent years to properly and timely track the environmental and climate processes in this vast region. In this regard, a satellite observing system on highly elliptical orbit (HEO) with 12-h period (Molniya type) is of particular interest, because it enables continuous coverage of the entire Arctic region (58°–90°N) from a constellation of two satellites. Canada is currently proposing to operate such a constellation by 2017. Extending the pioneering study of S. Q. Kidder and T. H. Vonder Haar, this paper presents in-depth analysis of spatiotemporal sampling properties of the imagery from this system. This paper also discusses challenges and advantages of this orbit for various applications that require high temporal resolution and angular sampling.

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Intercomparison of snowfall estimates derived from the CloudSat Cloud Profiling Radar and the ground based weather radar network over Sweden

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-8-8157-2015 ◽

2015 ◽

Vol 8 (8) ◽

pp. 8157-8189

Author(s):

L. Norin ◽

A. Devasthale ◽

T. S. L'Ecuyer ◽

N. B. Wood ◽

M. Smalley

Keyword(s):

High Latitude ◽

Precipitation Amount ◽

Weather Radar ◽

Probability Of Detection ◽

Polar Regions ◽

Rain Gauges ◽

Radar Network ◽

Skill Scores ◽

Satellite Sensors ◽

Observing Systems

Abstract. To be able to estimate snowfall accurately is important for both weather and climate applications. Ground-based weather radars and space-based satellite sensors are often used as viable alternatives to rain-gauges to estimate precipitation in this context. The Cloud Profiling Radar (CPR) onboard CloudSat is especially proving to be a useful tool to map snowfall globally, in part due to its high sensitivity to light precipitation and ability to provide near-global vertical structure. The importance of having snowfall estimates from CloudSat/CPR further increases in the high latitude regions as other ground-based observations become sparse and passive satellite sensors suffer from inherent limitations. Here we intercompared snowfall estimates from two observing systems, CloudSat and Swerad, the Swedish national weather radar network. Swerad offers one of the best calibrated data sets of precipitation amount at very high latitudes that are anchored to rain-gauges and that can be exploited to evaluate usefulness of CloudSat/CPR snowfall estimates in the polar regions. In total 7.2×105 matchups of CloudSat and Swerad over Sweden were inter-compared covering all but summer months (October to May) from 2008 to 2010. The intercomparison shows encouraging agreement between these two observing systems despite their different sensitivities and user applications. The best agreement is observed when CloudSat passes close to a Swerad station (46–82 km), when the observational conditions for both systems are comparable. Larger disagreements outside this range suggest that both platforms have difficulty with shallow snow but for different reasons. The correlation between Swerad and CloudSat degrades with increasing distance from the nearest Swerad station as Swerad's sensitivity decreases as a function of distance and Swerad also tends to overshoots low level precipitating systems further away from the station, leading to underestimation of snowfall rate and occasionally missing the precipitation altogether. Further investigations of various statistical metrics, such as the probability of detection, false alarm rate, hit rate, and the Hanssen–Kuipers skill scores, and the sensitivity of these metrics to snowfall rate and the distance from the radar station, were carried out. The results of these investigations highlight the strengths and the limitations of both observing systems at the lower and upper ends of snowfall distributions and the range of uncertainties that could be expected from these systems in the high latitude regions.

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Combined SMAP–SMOS thin sea ice thickness retrieval

The Cryosphere ◽

10.5194/tc-13-675-2019 ◽

2019 ◽

Vol 13 (2) ◽

pp. 675-691 ◽

Cited By ~ 11

Author(s):

Cătălin Paţilea ◽

Georg Heygster ◽

Marcus Huntemann ◽

Gunnar Spreen

Keyword(s):

Soil Moisture ◽

Sea Ice ◽

Brightness Temperature ◽

Incidence Angle ◽

Data Availability ◽

Ice Thickness ◽

Polar Regions ◽

Sea Ice Thickness ◽

Brightness Temperatures ◽

Spatial Coverage

Abstract. The spaceborne passive microwave sensors Soil Moisture Ocean Salinity (SMOS) and Soil Moisture Active Passive (SMAP) provide brightness temperature data in the L band (1.4 GHz). At this low frequency the atmosphere is close to transparent and in polar regions the thickness of thin sea ice can be derived. SMOS measurements cover a large incidence angle range, whereas SMAP observes at a fixed 40∘ incidence angle. By using brightness temperatures at a fixed incidence angle obtained directly (SMAP), or through interpolation (SMOS), thin sea ice thickness retrieval is more consistent as the incidence angle effects do not have to be taken into account. Here we transfer a retrieval algorithm for the thickness of thin sea ice (up to 50 cm) from SMOS data at 40 to 50∘ incidence angle to the fixed incidence angle of SMAP. The SMOS brightness temperatures (TBs) at a given incidence angle are estimated using empirical fit functions. SMAP TBs are calibrated to SMOS to provide a merged SMOS–SMAP sea ice thickness product. The new merged SMOS–SMAP thin ice thickness product was improved upon in several ways compared to previous thin ice thickness retrievals. (i) The combined product provides a better temporal and spatial coverage of the polar regions due to the usage of two sensors. (ii) The radio frequency interference (RFI) filtering method was improved, which results in higher data availability over both ocean and sea ice areas. (iii) For the intercalibration between SMOS and SMAP brightness temperatures the root mean square difference (RMSD) was reduced by 30 % relative to a prior attempt. (iv) The algorithm presented here allows also for separate retrieval from any of the two sensors, which makes the ice thickness dataset more resistant against failure of one of the sensors. A new way to estimate the uncertainty of ice thickness retrieval was implemented, which is based on the brightness temperature sensitivities.

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CHIMERE-2017: from urban to hemispheric chemistry-transport modeling

Geoscientific Model Development ◽

10.5194/gmd-10-2397-2017 ◽

2017 ◽

Vol 10 (6) ◽

pp. 2397-2423 ◽

Cited By ~ 76

Author(s):

Sylvain Mailler ◽

Laurent Menut ◽

Dmitry Khvorostyanov ◽

Myrto Valari ◽

Florian Couvidat ◽

...

Keyword(s):

Transport Model ◽

Model Simulation ◽

Point Of View ◽

Atmospheric Composition ◽

Test Case ◽

Polar Regions ◽

Chemistry Transport Model ◽

Computational Point ◽

Improve Model ◽

Code Complexity

Abstract. CHIMERE is a chemistry-transport model designed for regional atmospheric composition. It can be used at a variety of scales from local to continental domains. However, due to the model design and its historical use as a regional model, major limitations had remained, hampering its use at hemispheric scale, due to the coordinate system used for transport as well as to missing processes that are important in regions outside Europe. Most of these limitations have been removed in the CHIMERE-2017 version, allowing its use in any region of the world and at any scale, from the scale of a single urban area up to hemispheric scale, with or without polar regions included. Other important improvements have been made in the treatment of the physical processes affecting aerosols and the emissions of mineral dust. From a computational point of view, the parallelization strategy of the model has also been updated in order to improve model numerical performance and reduce the code complexity. The present article describes all these changes. Statistical scores for a model simulation over continental Europe are presented, and a simulation of the circumpolar transport of volcanic ash plume from the Puyehue volcanic eruption in June 2011 in Chile provides a test case for the new model version at hemispheric scale.

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Innovation in Satellite Sensors for Ocean Observations : An OceanObs19 overview

10.5194/egusphere-egu2020-7571 ◽

2020 ◽

Author(s):

Rosemary Morrow ◽

Keyword(s):

Wind Wave ◽

Multiple Scales ◽

Sar Interferometry ◽

Polar Regions ◽

Wave Interactions ◽

Ocean Fronts ◽

Satellite Sensors ◽

New Generation ◽

Ocean Observations ◽

Observing Systems

<p>Over the next decade, new satellite sensors are being developed or proposed to enhance our global observations of ocean surface parameters, many aiming at finer scale processes. These sensors include the new generation of satellite altimeters with finer resolution in alongtrack SAR mode or with swath SAR-interferometry; missions to observe total surface currents and wind-wave interactions; high resolution sea surface temperature and salinity; and ocean color, polarimetry and lidar missions for biogeochemistry, among others. Key observational challenges are to have finer-resolution across open ocean fronts, to observe the surface dynamical interactions over multiple scales, and to extend our satellite observing systems into the coastal and polar regions. Understanding smaller-scale variability will have benefits for climate, ocean operations and ocean health.</p><p>This presentation will give an overview of the OceanObs19 discussions on the opportunities and priorities for new satellite ocean sensors for the upcoming decade.</p>

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Simulations of M87 and Sgr A* imaging with the Millimetron Space Observatory on near-Earth orbits

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2709 ◽

2020 ◽

Vol 500 (4) ◽

pp. 4866-4877

Author(s):

A S Andrianov ◽

A M Baryshev ◽

H Falcke ◽

I A Girin ◽

T de Graauw ◽

...

Keyword(s):

Black Hole ◽

Space Mission ◽

Dynamic Imaging ◽

Image Resolution ◽

Fast Time ◽

Supermassive Black Hole ◽

Long Baseline ◽

Vlbi Observations ◽

Sgr A ◽

Earth Orbits

ABSTRACT High-resolution imaging of supermassive black hole shadows is a direct way to verify the theory of general relativity under extreme gravity conditions. Very Long Baseline Interferometry (VLBI) observations at millimetre/submillimetre wavelengths can provide such angular resolution for the supermassive black holes located in Sgr A* and M87. Recent VLBI observations of M87 with the Event Horizon Telescope (EHT) have shown such capabilities. The maximum obtainable spatial resolution of the EHT is limited by the Earth's diameter and atmospheric phase variations. In order to improve the image resolution, longer baselines are required. The Radioastron space mission successfully demonstrated the capabilities of space–Earth VLBI with baselines much longer than the Earth's diameter. Millimetron is the next space mission of the Russian Space Agency and will operate at millimetre wavelengths. The nominal orbit of the observatory will be located around the Lagrangian L2 point of the Sun–Earth system. In order to optimize the VLBI mode, we consider a possible second stage of the mission that could use a near-Earth high elliptical orbit (HEO). In this paper, a set of near-Earth orbits is used for synthetic space–Earth VLBI observations of Sgr A* and M87 in a joint Millimetron and EHT configuration. General relativistic magnetohydrodynamic models for the supermassive black hole environments of Sgr A* and M87 are used for static and dynamic imaging simulations at 230 GHz. A comparison preformed between ground and space–Earth baselines demonstrates that joint observations with Millimetron and EHT significantly improve the image resolution and allow the EHT + Millimetron to obtain snapshot images of Sgr A*, probing the dynamics at fast time-scales.

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Juegos de perspectivas: historia y ficción en "El viento de la luna" de A. Muñoz Molina

Monteagudo ◽

10.6018/monteagudo.472811 ◽

2021 ◽

pp. 229-245

Author(s):

Giovanna Fiordaliso

Keyword(s):

Essential Role ◽

Space Mission ◽

Point Of View ◽

The Novel ◽

The Real ◽

Historical Reality ◽

La Luna

Este trabajo analiza El viento de la luna, novela de 2006 de Muñoz Molina: es la historia de un chico de trece años que vive en Mágina, pequeña ciudad de provincia y que, fascinado por la misión espacial del Apolo XI y por las aventuras de su comandante, Neil Armstrong, asiste, más o menos consciente, al nacimiento de una nueva época. A través del punto de vista del protagonista, la realidad histórica de 1969 adquiere matices privados; al mismo tiempo, el cruce de miradas entre tierra y luna va a desempeñar un papel esencial en la novela, que se convierte en un canto de amor del autor hacia su país y hacia la literatura, fuente de consolación y sentido último de las experiencias. This work analyses the novel El viento de la luna, published in 2006 by Muñoz Molina: it is the story of a thirteen-year-old boy who lives in Mágina, fascinated by the Apollo XI space mission and by the adventures of its commander, Neil Armstrong. Through his point of view, the historical reality of 1969 acquires private nuances. At the same time, the exchange of the perspective between earth and moon plays an essential role in the novel, which becomes in this way a song of love of the author towards his country and towards literature, the real consolation and meaning of experiences.

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Liquid biopsies for omics-based analysis in sentinel mussels

10.1101/720219 ◽

2019 ◽

Author(s):

France Caza ◽

Philippine Granger Joly de Boissel ◽

Richard Villemur ◽

Stéphane Betoulle ◽

Yves St-Pierre

Keyword(s):

Liquid Biopsy ◽

Anthropogenic Activities ◽

Point Of View ◽

Cold Chain ◽

Great Promise ◽

Polar Regions ◽

Liquid Biopsies ◽

Fta Cards ◽

Ethical Point ◽

Comparable Performance

AbstractLiquid biopsy of plasma is a simple and non-invasive technology that holds great promise in biomedical research. It is based on the analysis of nucleic acid-based biomarkers with predictive potential. In the present work, we have combined this concept with the FTA technology for sentinel mussels. We found that hemocytes collected from liquid biopsies can be readily fixed on FTA cards and used for long-term transriptome analysis. We also showed that liquid biopsy is easily adaptable for metagenomic analysis of bacterial profiles of mussels. We finally provide evidence that liquid biopsies contained circulating cell-free DNA (ccfDNA) which can be used as an easily accessible genomic reservoir. Sampling of FTA-fixed circulating nucleic acids is stable at room temperature and does not necessitate a cold-chain protection. It showed comparable performance to frozen samples and is ideally adapted for sampling in remote areas, most notably in polar regions threatened by anthropogenic activities. From an ethical point of view, this minimally-invasive and non-lethal approach further reduces incidental mortality associated with conventional tissue sampling. This liquid biopsy-based approach should thus facilitate biobanking activities and development of omics-based biomarkers in sentinel mussels to assess the quality of marine ecosystems.

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