The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
resolution of 0.6 nm to enable the processing of the 5 nm and 
10 nm channel bandwidths of EnMAP. This “monochromatic” 
or fine spectral resolution database has to be resampled with the 
EnMAP channel filter curves. The advantage of compiling a 
“monochromatic” database is the possibility of quickly 
resampling it with updated spectral channel filter functions 
avoiding the necessity to run time-consuming radiative transfer 
calculations for the solar and view geometry pertaining to the 
acquired scenes. 
The EnMAP image processing will be performed with the 
ATCOR (atmospheric correction) code (e.g., Richter, R., 1996; 
Richter, R., 1998) that accounts for flat and rugged terrain, and 
includes haze/cirrus detection and removal algorithms. 
Output products will be the ground reflectance cube, maps of 
the aerosol optical thickness and atmospheric water vapor, and 
masks of land, water, haze, cloud, and snow. 
Water Applications 
A different strategy is employed for water applications 
exploiting the spectral properties of water, i.e. the low 
reflectance at wavelengths greater than 800 nm can be used to 
derive the aerosol map required for the retrieval of the map of 
water leaving radiance. In case of specular reflection (so-called 
“sun glint”) on water bodies, certain parts of the scene are 
contaminated with the glint signal. The glint signal can be 
removed to enable an evaluation of the water constituents in 
these areas. A distinctive, physical feature of remote sensing of 
water objects is that visible (and partial near infrared) radiation 
penetrates the water body and is reflected back in the direction 
of the sensor not only by the water surface, but also by deeper 
water layers. In this context, the radiative transfer model for 
processing of remote sensing water scenes should allow for the 
coupled treatment of radiation propagation in both atmosphere 
and water media. 
A number of radiative transfer codes allow for a coupled 
treatment of radiation propagation in atmosphere and water. 
One of the most widely applied of these is the finite element 
method. This method provides the possibility to obtain radiation 
intensities in all polar and azimuthal directions and it 
demonstrated better performance in the case with highly peaked 
phase functions, which are typical in the atmosphere and natural 
waters. In order to be used in an image processing system, the 
radiative transfer code must be supplemented by optical models 
of the atmosphere and water media. In particular, the MIP 
(Modular Inversion Program) (e.g., Heege, T. et al., 2005) is 
used, which combines the finite element method with the 
MODTRAN4 atmospheric model and the multi-component 
water model. 
Output products are the water reflectance cube, water 
constituents, the aerosol optical thickness map, and updates of 
masks of land, water, haze and cloud. 
4. VALIDATION 
In addition to the usage of internal calibration sources and sun 
calibration, vicarious validation is an essential part of the 
validation during the whole mission time. After launch, 
vicarious validation is the only possibility to verity the link 
between the data acquired by the instrument and the data 
measured at the Earth’s surface. A second topic is the 
verification of EnMAP level 1 and EnMAP level 2b products 
against reference measurements. Again vicarious validation is 
essential to detect sensor malfunction, calibration, and 
processing errors or insufficiencies. 
In order to ensure the spectral, radiometric, and geometric 
accuracy of the EnMAP level 1, 2a, 2b, and 2 products, they are 
periodically validated within time series and with data from 
other sources and of superior quality (i.e., data from airborne 
hyperspectral instruments, spectroscopic field measurements). 
Spectral/radiometric validation is conducted using repeated data 
acquisitions for well characterized and temporally stable areas 
and is further based on simultaneously acquired independent 
reference data measured in the field or using airborne 
spectrometers (e.g., Schroeder, M. et al., 2001; Teillet, P. M. et 
al., 2001). The in-flight geometric validation will assess the 
possible change of geometric parameters, e.g. the instrument or 
pixel boresight and the band-to-band registration of the VNIR 
and SWIR detector, by using ground control points and via the 
channels of the radiometric overlap region of the two sensors. 
These EnMAP calibration and validation activities are expected 
to be open for the support of the international user community. 
4.1 Spectral and Radiometric Validation 
For the validation of the EnMAP level 1 at-sensor radiance 
products, it is intended to use independent reference data 
(acquired by airborne sensors and/or by field instruments). 
These reference data sets (corrected to ground reflectances) will 
then be converted to top-of-atmosphere radiance values using 
atmospheric radiative transfer models. After that, the simulated 
level 1 data and the acquired EnMAP level 1 data will be 
analyzed, and a validation report will be written. In order to 
minimize the influence of the atmosphere, the reference site 
should be located in an environment with low atmospheric 
water vapor and dust load. Well known examples are Railroad 
Valley/Lunar Lake Playa (Nevada, USA) or Lake Frome 
(Australia). 
Assuming that such test areas are stable over time, some 
analysis can take place without the need for field data taken 
exactly during the EnMAP data acquisition. In this case 
EnMAP data from two or more data acquisitions are analyzed 
and compared to each other in order to detect changes in system 
performance. 
Also for the validation of EnMAP level 2 ground reflectance 
products independent reference data (acquired by airborne 
sensors or by field instruments) is required. In addition, an 
independently (offline) processed ground reflectance product 
will be generated using EnMAP level 1 data. After that, this 
independent reference data, this independently processed 
ground reflectance product, and the EnMAP level 2 product 
will be analyzed, and a validation report will be generated. The 
test sites for the validation of EnMAP level 2 products should 
include a variety of typical atmospheric conditions. Apart from 
spectral heterogeneity, there are no specific constraints on the 
sites and validation campaigns can be conducted together with 
other activities by DLR/GeoForschungsZentrum Potsdam like 
airborne hyperspectral campaigns or field spectroscopic 
measurements. 
4.2 Geometric Calibration and Validation 
Geometric processing of EnMAP scenes will be based on 
laboratory calibration, resulting in instrument to star-sensors