Whether for surface imagery, altimetry, studies of aerosols and clouds or recording the Earth’s magnetic field, satellites permit a global view of our Earth and in combination with more precise local in situ measurements offer enormous potential in understanding how the Earth ‘system’ works from the planet’s core out to the stratosphere, helping us to manage our Earth.
But, Earth sustained development is only feasible if a long-term program of Earth observation is undertaken to ensure service continuity. In order to accomplish this the Group on Earth Observations (GEO) is leading a worldwide effort to build a Global Earth Observation System of Systems (GEOSS) over a 10-year period. As a key component for GEOSS, Europe is developing the first operational monitoring systems for environment and security, the Global Monitoring for Environment and Security (GMES). These programs aim to coordinate satellite observation and in situ measurement activities, a method already and successfully used for meteorology and oceanography. GEO will focus on nine Societal Benefit Areas aiming to reduce humanity’s vulnerability to disasters and environmental change while enabling countries to better manage their agriculture, energy, water and other natural resources.
CNES, the French space agency, is strongly involved in these efforts either through national missions, often in multilateral cooperation with other space agencies, or through France’s participation in European Space Agency (ESA) Earth Observation Programs. All of these missions contribute either as demonstrators for new concepts or as first elements of operational series’ of satellites. They will provide data in most of the GEOSS Societal Benefit Areas including disaster response (Spot, Pléiades..), climate (Jason, SMOS, Calipso, Parasol, Mega Tropiques ), water (SMOS, Megha Tropiques, Vegetation…), weather (IASI..), and agriculture (Spot, Vegetation, Venμs..).
A brief description of these missions is given in the sections below.
|The SPOT 5 satellite maps terrain in three dimensions. The
above map shows the areas covered by the satellite.
1 ON GOING AND PLANNED MISSIONS
1.1 LAND OBSERVATORIES
Launched in 2002, SPOT 5 continues the SPOT line of satellites with an improved quality of images, ensuring a niche for future market needs.
While retaining the main characteristics of the Spot family, in particular its high acquisition capability with a 60Km field of view, SPOT 5 offers, with its two new HRG high resolution instruments, a better resolution, which permits differentiation of features as small as 2.5 meters.
It carries also a new high-resolution, stereoscopic imaging instrument, HRS. One telescope faces forwards and the other faces backwards, allowing the satellite to efficiently map terrain in three dimensions; more than 100 million square km are now available.
SPOT 5 images are already used in numerous applications, particularly in natural disaster management, mapping, urban planning agriculture and forestry management. The resources of the satellite operated by Spot Image are only just sufficient to satisfy the worldwide needs.
SPOT 5 remains in good condition and hasn’t yet to call on any of its backup systems. Ideally, its mission will continue through 2015.
|The Pléiades satellite.|
|Rapid mapping with Pléiades.|
The Pleiades Earth observation system will meet the needs of both civil and defense interests. It is the optical branch of the dual-use civil and military ORFEO system (Optical and Radar Federated Earth Observation) that is being developed with Italy.
Pléiades is composed of two “small satellites” that have a field of view of 20 km and a spatial resolution of 0.7 m. Their standout feature is agility enabling a daily access all over the world, a high coverage capacity and an along track stereoscopic acquisition capability. Thanks to all of these characteristics, Pléiades will be a strategic component of the GMES system by offering the fine cartography capability needed in most of the GEO’s Societal Benefit Areas and the daily revisit required by disasters management.
The first satellite will be operational beginning of 2010.
Since 1998, the Vegetation 1 and Vegetation 2 instruments, piggybacking on the SPOT 4 and SPOT 5 satellites, have monitored the Earth’s biosphere. They offer quasi daily earth coverage with a kilometric resolution in four spectral bands (blue, red, near infrared and short wave infrared). This permits generation, every 10 days, of a quasi cloud free synthesis of the planet’s biosphere.
|10-Day synthesis from Vegetation (September 11, 2002).|
Data from the Vegetation instruments are made accessible by Belgium (partner of the program with Sweden, Italy and the European Commission). Vegetation images are invaluable in forecasting crop yields and understanding plant cover’s role in carbon and water cycles on a global scale. Vegetation long term observation (a 10 years data base is available) is essential to better understand interactions between Earth’s biosphere and global changes.
|Slated for a 2009 launch, Venµs will monitor changes in plant
cover every two days.
The Vegetation and Environment Monitoring on a New Microsatellite (Venμs) mission is a joint French-Israeli venture whose aim is monitoring changes in plant cover every two days over predefined sites of interest, using a high-resolution superspectral camera (11 spectral bands). Currently scheduled for a 2009 launch, the two space agencies hope that data from Venµs will pave the way for land-use and vegetation monitoring services within the European GMES program.
1.2 OCEAN OBSERVATORIES
1.2.1 SMOS: SALT AND THE CLIMATE
|The SMOS will monitor surface soil
moisture and ocean surface salinity
for a variety of predictive
Even though both moisture and salinity are used in predictive atmospheric, oceanographic, and hydrologic models, no capability exists to date to measure directly and globally these key variables.
SMOS (Soil Moisture and Ocean Salinity) aims to fill this gap. The mission, scheduled for a 2008 launch, is a project jointly developed by the ESA, CNES and the Centro para el Desarrollo Technologico Industrial (CDTI), Spain’s space agency. The instrument, an L Band interferometric radiometer with a spatial resolution of 50 km, will measure every 3 days, on a global scale, surface soil moisture and ocean surface salinity.
Following the retirement of the Topex-Poseidon satellite due to a technical fault after more than thirteen years of exceptional services, Jason-2 is scheduled for a 2008 launch to join its predecessor, Jason-1 launched at the end of 2001. The satellites measure sea-surface height and are extremely sensitive to variations, detecting differences as small as a centimeter.
These missions will remain a reference in Earth observation as they laid the foundations of truly operational satellite oceanography. Data from these satellites are assimilated with in situ measurements into ocean-state forecasting models. This assimilation has now become a routine service provided by the Mercator Ocean public interest group.
|Satellites like Jason-2 offer valuable
insight into forecasting the oceans
and predicting currents.
|The Jason-2 measures sea-surface height, and is scheduled for a 2008 launch.|
In order to improve the current service and avoid any interruption, CNES decided, at the end of 2005, to develop the AltiKa altimetry payload in Ka band.
This high-resolution instrument will offer a small footprint (5km) and high vertical resolution. It will meet the needs of a new range of applications by providing a description of the ocean at the meso scale in the open ocean and in coastal areas.
AltiKa will be launched in 2009 on the SARAL (Satellite with ARgos and ALtika) satellite jointly designed with the Indian Space Research Organisation (ISRO), the Indian Space agency.
1.3 ATMOSPHERE OBSERVATORIES
|IASI records levels of radiance in order to derive profiles
of temperature and humidity.
1.3.1 IASI FOR MORE ACCURATE WEATHER FORECASTS
|IASI: an infrared sounding
Launched as a payload of the METOP meteorological satellites at the end of 2006, IASI (Infrared Atmospheric Sounding Interferometer) is a significant technological and scientific step forward allowing measurements of atmospheric radiances in more than 8,000 infrared channels.
These radiances are assimilated by meteorologists into operational weather forecasting models to derive atmospheric temperature and humidity profiles. It is a major advance in weather forecasting.
The IASI data will also be used by scientists for atmospheric chemistry studies.
IASI is a joint project between the CNES and Eumestat (European Organisation for the Exploitation of Meteorological Satellites), the European organization for operation of such satellites.
Service continuity will be ensured up to 2020.
1.3.2 PARASOL AND CALIPSO: THE EFFECTS OF CLOUDS AND AEROSOLS ON CLIMATE
What role do aerosols play in climate processes? How will cloud cover change as a consequence of global warming? How do clouds and aerosols interact? These are some of the questions to be answered by the Parasol mission (Polarization and Anisotropy of Reflectances for Atmospheric Science coupled with Observations from a Lidar) and the French-American Calipso mission.
Parasol, a low cost microsatellite launched in December 2004, was designed to improve our knowledge of the radiative and microphysical properties of clouds and aerosols by measuring the directionality and polarization of light reflected by the Earth-atmosphere in 9 spectral bands with a wide swath of 2400km.
The joint NASA/CNES Calipso mission, launched in 2006 with Cloudsat, provides a vertical view of aerosols and thin clouds beneath the satellite. Calipso data enables scientists to characterize the vertical distribution and microphysics of aerosols and thin clouds.
The Calipso satellite, which uses the French standard Proteusplatform, has a payload composed of one backscattering lidar, provided by NASA, and an infrared imager provided by CNES.
|Parasol collects data on the interaction between clouds and
aerosols. Small aerosols (<0.35 μm) in August 2005.
|Calipso works in conjunction with other satellites
to deliver data on clouds.
These two missions complete the measurements of other instruments in the international A-Train Space observatory, including the CERES and MODIS radiometers on Aqua, and the radar on Cloudsat which permits to analyze thick clouds.
1.3.3 MEGHA-TROPIQUES AND THE WATER CYCLE
The French-Indian Megha-Tropiques mission is designed to investigate atmospheric circulation, the water cycle and climate change. Circling Earth on a slightly inclined orbit, this research satellite will clarify how the water cycle affects the dynamics of the tropical atmosphere.
Scheduled to be launched in 2009, its payload consists of three instruments:
– MADRAS: a microwave imager aimed mainly at studying precipitation and clouds properties. MADRAS is a conical scanning radiometer with operating frequencies in the range 18,7 GHz-157 GHz.
– SAPHIR: a 6-channel microwave radiometer in the 183,31 GHz +/- 12 GHz bandwidth used to retrieve water vapor vertical profiles and horizontal distribution,
– SCARAB: a cross track scanning radiometer that measures outgoing radiative fluxes at the top of the atmosphere
|The Megha-Tropiques will carry three instruments for
measurement of precipitation and water vapor profiles.
The satellite will cover the tropical belt from 23°N to 23°S with at least 3 measurements per day. The smallest details deal with the convective precipitation field, with a size of individual convective cell of about 10 km.
1.4 SOLID EARTH
1.4.1 MEASURING THE EARTH’S MAGNETIC FIELD
It is important to study Earth’s magnetic field, as it is our protective shield from ionized particles coming from the sun. The specifics of the magnetic field’s functions are not still well known. Three missions are currently measuring the Earth’s magnetic field: the Danish satellite Oersted, launched in 1999, the German CHAMP and the Argentinean SAC-C. The latter two were launched in 2000.
The Swarm project, set by the ESA for 2010, will be a constellation of three identical satellites in different orbits defined to optimize separation of the contribution of each source of the Earth’s magnetic field in the models. CNES will supply the mission’s absolute magnetometers developed by the LETI/CEA laboratory.
1.4.2 MEASURING THE EARTH’S GRAVITY FIELD
The measurement of the static, or mean, part of the gravity field is of major importance to provide the reference surface, called geoid, needed for many applications as oceanography to deduce mean sea level and currents. The gravity field model, and the gravity gradients, will also be very useful to geophysical studies and geodesy.
By closely studying perturbations in the orbits of LEO satellites, one can measure lateral variations in the gravity field which mirror changes in mass in the Earth’s interior and on its surface.
Two missions are currently measuring the Earth’s gravity field using ONERA-developed accelerometers: the German CHAMP satellite, launched in 2000 and the American Grace mission, launched in 2002.
ESA will launch the GOCE mission in 2008. Due to a lower orbit (270km) and a highly-specialized principal instrument which will measure the gravity field gradient in three directions in Space, GOCE should enable us to measure the Earth’s gravity field with great precision and model the Earth’s geoid with unparalleled precision (up to within around 1 cm of geoid height).
The CNES Space Geodesy team is a member of the EGGC consortium (European Gravity Gradient Consortium) selected by ESA for the mission’s data processing, and particularly for the gravity field modeling by means of the direct numerical method.
1.4.3 DORIS, THE SPACE SURVEYOR
DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) was designed to help determine Earth’s geodetic parameters, such as center of mass and surface movements.
The precise positioning is based on Doppler-shift measurements of radio frequency signals transmitted by a world-wide beacon network.There are five DORIS instruments in orbit. Two are flying on SPOT 2 and SPOT 4, and three newer instruments are onboard Jason-1, Envisat and SPOT 5. Future DORIS missions will fly with oceanographic altimetry missions as Jason-2 in 2008, India’s AltiKa in 2009 and ESA Cryosat 2 in 2009.
|Demeter is focused on collecting
data on atmospheric disturbances.
1.4.4 DEMETER, LISTENING TO EARTHQUAKES
Demeter (Detection of Electro-Magnetic Emission Transmitted from Earthquake Regions), is the first satellite in CNES Myriade microsatellite series. It studies disturbances in the upper atmosphere related to earthquakes, volcanic eruptions or tsunamis (tidal waves).
This pathfinder mission, launched in June 2004, is gathering a wealth of data on the Earth’s electromagnetic environment and succeeded in measuring events related to the Earth’s electromagnetic environment, seismic activity and human activity.
1.5 THE INTERNATIONAL CHARTER “SPACE AND MAJOR DISASTERS”
CNES is involved in the International Charter “Space and Major Disasters,” which aims at providing a unified system of space data acquisition and delivery to those affected by natural or man-made disasters through Authorized Users. It supplies emergency organization in the response phase with coordinated and free access to space systems services (such as rapid mapping) to improve their efficiency in the event of a disaster.
The Charter, triggered by Civil Protections or Emergency & Rescue Services, and UN specialized agencies, is based on available effort and has no financial exchange. From November 2000 to September 2007, it has been activated 147 times across various continents.
2 FUTURE PREPARATION
CNES has numerous future objectives, including improving the performance of space observatories, gaining access to new kinds of measurements and reducing the overall costs of observatories to allow true service continuity.
For risk management observatories, approaches to improve the reactivity and the revisit (up to 3 hours) capability of metric optical systems are being considered.
In the area of land observatories, CNES is working on a low-cost thermal infrared demonstrator with a decametric resolution dedicated to the evaluation of water and energy fluxes. New kinds of measurement are also being considered, such as a lidar altimeter for 3D mapping of coastal areas and vegetation structure with the objective to clarify the need for, the feasibility of and the identity of the critical technologies. Furthermore, an innovative concept on an e-constellation for internet mass market is under study (the Earth mapped every day with a metric resolution).
Concerning ocean observatories, CNES is hoping to improve the measurement of oceanic circulation and research in continental hydrology with a new concept of altimeters, the wide swath interferometric Ka band altimeter (SWOT) in close cooperation with our historical partners NASA, NOAA (National Oceanic and Atmospheric Administration) and Eumetsat. Finally the CNES is researching a permanent observatory to collect data on rapidly changing coastal regions.
Regarding atmospheric applications, improvement of IASI and Parasol instruments is underway for the next generation of Metop satellites. As air quality is one of the main challenge in the health Societal Benefit Areas, dedicated missions are under study. Such a mission (Traq) was among the 6 Earth Explorer core missions selected by ESA for preliminary studies. In parallel CNES is conducting a definition study on one of the instrument, an innovative Static Infrared Fourier Transform Interferometer (SIFTI).
By all these missions, CNES is strongly involved in the GEO Work plan. These projects contribute to international cooperation and coordination in several Social Benefit Areas such as Disasters, Human Health, Climate, Weather, Water Cycle, and Agriculture.
CNES is also active in the international coordination effort by its participation in the CEOS working groups for education, calibration/validation (also through GSICS group led by WMO) and in the CEOS reflections on virtual constellation for land monitoring, precipitation, atmospheric chemistry and altimetry.