AIM-North is a proposed satellite mission that would provide observations of unprecedented frequency and density for monitoring northern greenhouse gases (GHGs), air quality (AQ) and vegetation. ...AIM-North would consist of two satellites in a highly elliptical orbit formation, observing over land from ∼40°N to 80°N multiple times per day. Each satellite would carry a near-infrared to shortwave infrared imaging spectrometer for CO
2
, CH
4
, and CO, and an ultraviolet-visible imaging spectrometer for air quality. Both instruments would measure solar-induced fluorescence from vegetation. A cloud imager would make near-real-time observations, which could inform the pointing of the other instruments to focus only on the clearest regions. Multiple geostationary (GEO) AQ and GHG satellites are planned for the 2020s, but they will lack coverage of northern regions like the Arctic. AIM-North would address this gap with quasi-geostationary observations of the North and overlap with GEO coverage to facilitate intercomparison and fusion of these datasets. The resulting data would improve our ability to forecast northern air quality and quantify fluxes of GHG and AQ species from forests, permafrost, biomass burning and anthropogenic activity, furthering our scientific understanding of these processes and supporting environmental policy.
This book uses an algebraic approach that can be introduced as a tensor product of quaternion algebras and provides a unified calculus for much of physics. It proposes a pedagogical introduction to ...this new calculus, based on quaternions.
The Hydrosphere State Mission (Hydros) is a pathfinder mission in the National Aeronautics and Space Administration (NASA) Earth System Science Pathfinder Program (ESSP). The objective of the mission ...is to provide exploratory global measurements of the earth's soil moisture at 10-km resolution with two- to three-days revisit and land-surface freeze/thaw conditions at 3-km resolution with one- to two-days revisit. The mission builds on the heritage of ground-based and airborne passive and active low-frequency microwave measurements that have demonstrated and validated the effectiveness of the measurements and associated algorithms for estimating the amount and phase (frozen or thawed) of surface soil moisture. The mission data will enable advances in weather and climate prediction and in mapping processes that link the water, energy, and carbon cycles. The Hydros instrument is a combined radar and radiometer system operating at 1.26 GHz (with VV, HH, and HV polarizations) and 1.41 GHz (with H, V, and U polarizations), respectively. The radar and the radiometer share the aperture of a 6-m antenna with a look-angle of 39° with respect to nadir. The lightweight deployable mesh antenna is rotated at 14.6 rpm to provide a constant look-angle scan across a swath width of 1000 km. The wide swath provides global coverage that meet the revisit requirements. The radiometer measurements allow retrieval of soil moisture in diverse (nonforested) landscapes with a resolution of 40 km. The radar measurements allow the retrieval of soil moisture at relatively high resolution (3 km). The mission includes combined radar/radiometer data products that will use the synergy of the two sensors to deliver enhanced-quality 10-km resolution soil moisture estimates. In this paper, the science requirements and their traceability to the instrument design are outlined. A review of the underlying measurement physics and key instrument performance parameters are also presented.
Hyperquaternion Conformal Groups Girard, Patrick R.; Clarysse, Patrick; Pujol, Romaric ...
Advances in applied Clifford algebras,
07/2021, Letnik:
31, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The paper gives a new representation of conformal groups in
n
dimensions in terms of hyperquaternions defined as tensor products of quaternion algebras (or a subalgebra thereof). Being Clifford ...algebras, hyperquaternions provide a good representation of pseudo-orthogonal groups such as
O
(
p
+
1
,
q
+
1
)
isomorphic to the
nD
conformal group with
n
=
p
+
q
.
The representation yields simple expressions of the generators, independently of matrices or operators. The canonical decomposition and the invariants are discussed. As application, the 4
D
relativistic conformal group is detailed together with a worked example. Finally, the formalism is compared to the operator representation. Potential uses include in particular, conformal geometry, computer graphics and conformal field theory.
A spaceborne radar for atmospheric observation must be able to detect atmospheric backscatter in the presence of clutter from the surface, due to antenna sidelobes. Such clutter can come from the ...same pulse as that observing the atmosphere if the radar antenna is pointed off-nadir. However pulses both prior and subsequent to the pulse observing the atmosphere can also contribute to clutter, and surface clutter can be a problem even for nadir-looking radars. Here, the problem is analyzed by deriving a method for computing clutter which includes effects of all contributing transmit pulses, Doppler shifting, finite receiver bandwidth, and curved Earth's surface. The results are applied to analysis of existing radars and design of future radar systems.
The goal of the Canadian Hyperspectral Mission (CHM) is to provide a new and powerful space-based tool for delivering frequently updated hyperspectral remote sensing information products for a broad ...range of operational users in governments and industries worldwide. The resulting CHM concept includes a relatively low cost constellation of three microsatellites and a supporting ground segment which, together, would be capable of imaging the entire land mass and coastal areas of Canada, USA and Europe every 3 days.
The Canadian Space Agency (CSA) has initiated several studies on possible missions addressing the needs of Canadian government departments for operational land and ocean applications. Three parallel ...studies have been completed that reviewed the requirements with an objective to identify microsatellite mission concepts. The CSA has further awarded two contracts to the Canadian industry teams to investigate the feasibility of hyperspectral imagers that are compatible with a microsatellite platform. Two different concepts of low-mass imaging systems have been proposed and studied. In order to address to the main challenges identified, the CSA has extended the two feasibility studies. This paper briefly reports the updates of the feasibility studies in the extension period and new development in the ongoing concept study of a Canadian hyperspectral mission.
The Canadian Space Agency (CSA) in collaboration with the Naval Research Laboratory (NRL) and NASA are considering a coastal and inland water color hyperspectral imager as a complement to the NASA's ...Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission. This hyperspectral imager with 100 m spatial sampling would be specifically designed to sample the coastal oceans, estuaries and lakes, and will help improve the monitoring and better understand quality and productivity of coastal and inland waters and their impact on the coastal communities' well-being and economic activities. This paper describes the user community needs for spaceborne fine-spatial-resolution coastal and inland water hyperspectral imaging, the specifications of the hyperspectral payload that addresses the users' needs, payload concept design and related technical challenges.
In order to meet the needs of Canadian government departments for operational land and ocean applications the Canadian Space Agency in collaboration with its industry has carried out activities and ...initiated early phase studies to investigate the feasibility of hyperspectral imager that is compatible with a microsatellite platform. Feasibility studies on two different concepts of microsatellite hyperspectral imagers are ongoing. A user evaluation study that assesses the key parameters of the microsatellite has completed. This paper briefly summarizes the development and early results of the feasibility studies and user assessment.
The HYDROS mission is under development by NASA as part of its Earth System Science Pathfinder (ESSP) program. HYDROS is designed to provide global maps of the Earth's soil moisture and freeze/thaw ...state every 2-3 days, for weather and climate prediction, water, energy and carbon cycle studies, natural hazards monitoring, and national security applications. HYDROS uses a unique active and passive L-band microwave system that optimizes measurement accuracy, spatial resolution, and coverage. It provides measurements in nearly all weather conditions, regardless of solar illumination. The design of the radar and radiometer electronics, antenna feed system, reflector and science data system, are driven by specific mission and science objectives. These objectives impose requirements on the frequencies, polarizations, sampling, spatial resolution, and accuracy of the system. We describe the HYDROS mission requirements, baseline design, and measurement capabilities.
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