User Guideline
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Only one GOME-2 surface LER database exists, based on observations of 
the Earth's surface performed by the GOME-2 instruments onboard the 
MetOp-A and MetOp-B satellites. However, this merged GOME-2 surface LER 
product contains two surface LER versions: one version based on GOME-2 
observations by the Main Science Channels (MSCs) and one version based 
on GOME-2 observations by the Polarisation Measurement Devices (PMDs).

The MSC-LER will be the most logical choice for most users. The PMD-LER 
is intended for users that need surface albedo input for their (GOME-2) 
PMD band retrievals, or that really need the higher intrinsic resolution 
of the PMD-LER. The MSC-LER and PMD-LER databases are each contained in 
a separate NetCDF-4 file.

The MSC-LER and PMD-LER products both contain two types of fields: the 
MIN-LER and MODE-LER fields. The meaning of these two types of fields is 
explained in section 3.6 of the Product User Manual (PUM). The PUM also 
provides a suggestion as to which field to use for which situation.

This version of the database also contains BRDF-like information about 
the directional dependence of the surface reflectivity. The calculation 
of the directionally dependent Lambertian-equivalent reflectivity (DLER) 
is discussed in detail in section 3.3 of the PUM. The DLER may be used 
as input for satellite retrievals based on the GOME-2 instruments, but 
also for those based on other satellite instruments in similar orbits 
with a similar equator crossing time. This includes, for instance, the 
GOME-1, SCIAMACHY, MERIS, AVHRR, and Sentinel-5/UVNS instruments.