A new call for Core Earth Explorer Ideas was released by the European Space Agency in March 2005. The Call focused
on the global carbon and water cycles, atmospheric chemistry and climate, as well as the human element as a cross
cutting issue. The proposals were peer reviewed by scientific panels, and also appraised technically and
programmatically by ESA. This paper describes the Earth Explorer cycle and gives an overview of the six candidate
missions selected for assessment studies.
The Living Planet Programme of the European Space Agency encompasses a science-driven strategy for monitoring the
Earth from space. The Earth Explorer missions are defined, developed and operated in close cooperation with the science
community and focus on the key components of the Earth System: the atmosphere, biosphere, hydrosphere, cryosphere
and the Earth's interior. The emphasis of these missions is on providing data to advance our understanding of these
individual components, their interaction with each other and the impacts that human activities have on natural Earth
processes.
By involving the science community from the beginning and introducing a peer-reviewed selection process, this ongoing
user-driven approach has given the Earth science community an efficient tool in their endeavor to better
understand and monitor our planet. So far, this process has resulted in six missions currently under development: GOCE,
Cryosat, ADM Aeolus, SMOS, Swarm and EarthCARE.
The third cycle of Earth Explorers Core Missions was started in 2005 to select the seventh Earth Explorer mission due to
launch in 2014/2015. At present there are six candidate missions being assessed at pre-phase A level. These missions
were chosen to enter the assessment phase as a result of the Call for Core Mission ideas released by ESA in 2005, which
resulted in 24 proposals out of which six candidates were selected:
- BIOMASS - global measurements of forest biomass and extent;
- TRAQ - (TRopospheric composition and Air Quality) - Air quality monitoring and long-range transport of air
pollutants;
- PREMIER - (PRocess Exploration through Measurements of Infrared and millimetre-wave Emitted Radiation)
Understanding the processes that link trace gases, radiation, chemistry and climate in the atmosphere;
- FLEX - (FLuorescence EXplorer) - Observation of global photosynthesis through the measurement of fluorescence;
- A-SCOPE - (Advanced Space Carbon and Climate Observation of Planet Earth) - Improving the understanding of
the global carbon cycle and regional carbon dioxide fluxes;
- CoReH2O - (Cold Regions Hydrology High-resolution Observatory) - Detailed observations of key snow, ice and
water cycle characteristics.
This paper presents an overview of the six candidate missions, describing the scientific objectives and outlining the main
aspects of the candidate implementation concept currently under evaluation.
A constellation of satellites that routinely and frequently images the Earth's land surface in consistently
calibrated wavelengths from the visible through the microwave and in spatial detail that ranges from submeter
to hundreds of meters would offer enormous potential benefits to society. A well-designed and
effectively operated land surface imaging satellite constellation could have great positive impact not only on
the quality of life for citizens of all nations, but also on mankind's very ability to sustain life as we know it on
this planet long into the future.
The primary objective of the Committee on Earth Observation Satellites (CEOS) Land Surface Imaging (LSI)
Constellation is to define standards (or guidelines) that describe optimal future
LSI Constellation capabilities,
characteristics, and practices. Standards defined for a LSI Constellation will be based on a thorough
understanding of user requirements, and they will address at least three fundamental areas of the systems
comprising a Land Surface Imaging Constellation: the space segments, the ground segments, and relevant
policies and plans. Studies conducted by the LSI Constellation Study Team also will address current and
shorter-term problems and issues facing the land remote sensing community today, such as seeking ways to
work more cooperatively in the operation of existing land surface imaging systems and helping to accomplish
tangible benefits to society through application of land surface image data acquired by existing systems.
2007 LSI Constellation studies are designed to establish initial international agreements, develop preliminary
standards for a mid-resolution land surface imaging constellation, and contribute data to a global forest
assessment.
Two field experiments named WISE (WInd and Salinity Experiment) were sponsored by the European Space Agency (ESA) to better understand the wind and sea state effects on the L-band brightness temperatures. They took place at the Casablanca oil rig located in the North Mediterranean Sea, 40 km off shore the Ebro river delta: WISE 2000 from November 25 to December 18, 2000, and continued during the January 9 to 16, 2001, and WISE 2001 from October 23 to November 22, 2001. During the spring of 2003, under Spanish National funds, a third field experiment named FROG (Foam, Rain, Oil slicks and GPS reflectometry) took place at the Ebro river delta, to measure the phenomena that were not completely understood during the WISE field experiments, mainly the effect of foam and rain. In order to achieve the objectives of the WISE field experiments the LAURA L-band fully polarimetric radiometer from the Technical University of Catalonia (UPC) was mounted on the Casablanca oil-rig at the 32 meters deck above the sea surface, pointing to the North and North-West, in the direction of the dominant winds. In this paper we present the results of the first study to determine the relationship between the brightness temperature and the sea state.
The Soil Moisture and Ocean Salinity Mission is currently in the design and development phase (Phase-B) and scheduled for launch in early 2007. SMOS will exploit an innovative instrument designed as a two-dimensional interferometer for acquiring brightness temperature observations at L-band (1.4 GHz) globally and with a revisit time less than 3 days, a spatial resolution of smaller than 50km, and with a range viewing angles (0-50 degrees) for the estimation of soil moisture and ocean salinity, both are key variables used in weather, climate and extreme-event forecasting. As a secondary objective data acquired by SMOS over ice/snow regions may prove useful to characterise the ice and snow
layers and thus complement other satellite observations to advance the science of the cryosphere (see also
http://www.esa.int/livingplanet).
A number of open scientific questions related to the physics of the signal, perturbing effects and the retrieval concept by accounting on SMOS observational characteristics needed to be addressed to prepare for the mission. In addition, appropriate campaigns were designed and organised to provide suitable data for the analysis. This included the analysis of the physics of the signal (sensitivity towards ocean salinity, soil moisture and perturbing effects), the analysis of the data product requirements of the user community and the development of retrieval concepts. Campaign activities included the WISE, LOSAC, and EuroSTARRS campaigns.
This paper is intended to summarise the activities performed so far to advance our knowledge of the microwave radiation emitted by the Earth at L-band, the capability to retrieve soil moisture and ocean salinity from it and its dependence on other factors. It will also give an outlook of future planned activities to prepare for SMOS mission.
The fluorescence signal emitted from vegetation is directly linked to the photosynthesis and as such may be used as an indicator for plant functioning, stress and vitality. Observation of solar induced fluorescence from space is proposed by measuring the weak signal contribution in the Fraunhofer line wavelengths. In an ESA funded study various aspects of measuring the fluorescence signal from space have been analysed for it's feasibility. Both scientific and instrumental aspects have been considered in the analysis. The scientific requirements have been studied in detail, looking to aspects such as the selection of Fraunhofer lines, the solar induced fluorescence radiance, measurement accuracy, spatial resolution, atmosphere influence, etc. This has resulted in instrument requirements, that are the basis for a trade off study of optical observation techniques. The main choice was between applying a grating spectrometer or a filter spectrometer, each having advantages and disadvantages for Fraunhofer line detection (FLD). From both spectrometer types a preliminary optical design has been made. Besides a model has been developed to evaluate the different configurations for S/N, integration time, radiance level etc. For these calculations it appeared, that the information about solar excited fluorescence intensity of vegetation is minimal. In the study of feasibility of Fraunhofer line detection from space is demonstrated, albeit, that the observation strategy will depend on the real amount of the solar excited fluorescence intensity. The results of the study are a good basis for further development of a spaceborn Fraunhofer line detector.
The SMOS L-band 2-D interferometer is based on an innovative concept of bi-dimensional aperture synthesis method. The instrument is a Y shaped structure consisting of 3 coplanar arms. The sensor has new and very significant capabilities especially in terms of multi-angular view configuration.. This paper will describe the SMOS concept in terms of instrument (characteristics) investigates the main aspects of the retrieval capabilities of the 2-D microwave interferometer for monitoring soil moisture, vegetation biomass and surface temperature. The analysis is based on model inversion taking into account the instrument characteristics. The standard error of estimate of the surface variables is computed as a function of the sensor configuration system and of the uncertainties associated with the spatial measurements. The inversion process is based on a standard minimisation routine that computes both retrieved variables and standard error associated with the retrievals. The potential of SMOS, depending on the view angle configuration and the use of the sole 1.4 GHz is investigated. These questions are key issues to define the observation configuration of SMOS that meets the scientific requirements and the technical constraints of the spatial missions.
The Earth Explorer Missions are research/demonstration missions for Earth Observation that are planned for implementation in the frame of the European Space Agency's 'Living Planet' Programme. The program focuses on advancing understanding of different processes that contribute to govern the Earth Systems. One of the four Earth Explorer Missions which was the subject of a Phase A study is the Land-Surface Processes and Interactions Mission (LSPIM). The scientific objectives are the study of land surface processes and their interactions with the atmosphere. It focuses on the measurement of surface characteristics such as albedo, reflectance, bidirectional reflectance distribution function (BRDF) and surface temperature, which are linked to the processes driving bio/geophysical and biochemical variables. To fulfil the mission requirements a hyperspectral imager is proposed as the LSPIM core instrument. The LSPIM imaging spectrometer will provide contiguous spectral coverage in 142 bands within the VIS/NIR/SWIR spectral region with spectral resolution between 10 and 15 nm. Furthermore, TIR observations will be performed by a radiometer in two wavebands. A spatial resolution of 50 m X 50 m with a swath width of 50 km at nadir will be provided. This mission will also have a de- pointing capability for BRDF observations along-track and areal access across-track such that each site of interest can be revisited at 3 days intervals. It is the purpose of this paper to outline the planned spaceborne mission, its scientific objectives and the derived system requirements.
One of the elements of the European Space Agencies new 'Living Planet' Programme for Earth Observation are the Earth Explorer Missions. These are research/demonstration missions with the emphasis on advancing understanding of different processes, which help govern the Earth Systems. One of the four Earth Explorer Missions which was subjected to a Phase A study is the Land Surface Processes and Interactions Mission (LSPIM). The major scientific objective of the LSPIM is to increase our understanding of land-surface processes and interactions. In order to retrieve relevant geo-/biophysical variables needed to feed and adjust the models describing the processes and interactions, detailed information at high spatial, spectral, directional and temporal resolution is required. To fulfill the mission objectives, a hyperspectral imager is proposed as the LSPIM instrument. The mission will provide contiguous spectral coverage in 142 bands within the solar spectral region (0.45 - 2.35 micrometer). The spectral sampling interval will be 10 nm in the VNIR and 15 nm in the SWIR. Further TIR observations will be performed in two wavebands. A spatial resolution of 50 m X 50 m with a swath width of 50 km will be provided. This mission will also have a depointing capability for angular observations along-track and areal access across track. Seven directions from which one is programmable available for angular observation. It is the purpose of this paper to outline the planned spaceborne mission.
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