2.1 The POEM Programme 
Drawing on the mission requirements of ERS-1 and ERS-2, ESA has extended its requirements to a programme 
of new polar orbiting systems. Under the ESA Polar Orbit Earth observation Missions programme (POEM), 
two satellites are being developed: the ENV1SAT-1 and METOP platforms. The mission objectives for the 
ГОЕМ programme are to identify and advance the understanding of relevant processes to monitor the state of the 
Earth/atmosphere system. The mission goals include: 
• continuity of ongoing European remote sensing projects such as ERS-1 
• contribution to operational meteorology 
• environmental studies including chemistry 
The mission will complement both national and international ongoing programmes and provide a technically 
realistic, feasible and cost effective polar orbiting system. 
2.2 Meteosat Second Generation 
From geostationary orbit, MSG will focus on operational meteorology applications but will also contribute to 
land applications on a large spatial scale. The spectral bands have a sampling distance of 3km at sub satellite 
point and in addition a high resolution visible band with a 1km sampling distance at SSP. The second 
generation will greatly improve upon the land applications capability of the current operational Meteosat system 
through its improved spatial, spectral and temporal characteristics. 
2.3 POEM-Next 
ESA is considering many potential instruments for future missions beyond 2000. Following discussions with a 
large section of the remote sensing community a prime candidate for a future mission would be a dedicated land 
mission sensing at high spatial and spectral resolution. 
The primary objective of a high resolution land surface mission is to increase the understanding of 
land/atmosphere interactions at the local scale in order to advance understanding of interactions on the regional 
and global scale. This high spatial resolution imaging facility will help to fully understand the averaged 
response of coarse resolution imaging sensors, such as AATSR, AVHRR, MERIS, and MODIS, used in their 
operational role of monitoring Earth fluxes. 
3. THE LAND SURFACE PROCESSES MISSION 
ESA has recognised, via its Science Advisory Group on Land Surface Processes, the need for a high spatial and 
high spectral resolution mission addressing land surface processes issues. It has also recognised the need to 
acquire data over a wide wavelength range from the visible through to the thermal infrared to obtain 
complementary information needed for input into the various processes models. 
For some time ESA has been studying critical technology issues to establish the feasibility of a High 
Resolution Imaging Spectrometer (HRIS) and a High Resolution Thermal Infrared Radiometer (HRTIR). 
Subsequently, a feasibility study has been initiated under the auspices of the Earth Observation Preparatory 
Programme (EOPP) for a high resolution land surface processes mission which will combine many of the 
capabilities of the two instruments concepts. This facility is entitled "PRISM" (Processes Research by an 
Imaging Space Mission). 
To realise the primary objectives of the land processes mission, PRISM will create data sets on the intermediate 
scale of 10's of metres which can be verified by field experiments. These data can then be used as input to sub- 
mesoscale GCM's, or Soil-Vegetation-Atmosphere Transfer (SVAT) models, forming the basis for nested 
models. Thus such a mission will forge an effective link between ground truth observations and regional and 
global scale remote sensing data sets. 
The high spectral resolution capability foreseen for PRISM is required to resolve the subtle differences and 
changes in response caused by the processes to be studied.