We propose to map the Orion-B molecular cloud complex (L1630), including
NGC2023, NGC2024, IC434, and the Horsehead Nebula B33,
using the ISOPHOT C200 camera and the 200 um filter.
Our ISO 200/100um mapping program of molecular clouds in
the DLEMKE.ISDUST GT Program has been very succesful and has
shown that the ISOPHOT 200 um capability enables us to detect
the very cold dust condensations in dense molecular cloud targets
which are probably the earliest pre-protostellar stages, most of them
not detected by IRAS at 100 um.
Because of the visibility constraints the Orion-B Molecular Cloud was
not included in our original autumn launch target list. Neither is it
being mapped at 200 um by any other ISO observer(s).
The Orion-B Molecular Cloud is, however, one of the best-studied
star formation regions in our neighbourhood and, besides Orion A, the
nearest one having also high mass star formation.  The ISOPHOT 200 um
mapping would provide a new and unparalleled data set for Orion-B and
would be of high interest also in comparison with our 200 um map of the
Orion A Cloud. Because of its short distance Orion-B will also serve as
a template object for other, more distant star formation regions.
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