Molecular hydrogen (H2) is the most important tracer of velocity
 shocks in the bow shocks of well-collimated Herbig-Haro (HH) jets and
 also in less well-collimated molecular outflows. Yet not much is known
 about which type of molecular physics is appropriate for these objects
 and which flow pattern (e.g., J shocks or C shocks) excites the H2.
 Only two outflows have been studied in detail so far, with differing
 results. What is clearly necessary to understand the shock structures
 that arise in the shock waves of bipolar outflows is the knowledge of
 the excitation state of the gas as measured by the column density of
 H2 in each energy level in a number of typical objects. However, only
 lines arising from energy levels higher than about 6000 K are
 accessible from the ground. We therefore propose to derive spatially
 resolved level column densities from the purely rotational transitions
 of the H2 molecule from energy levels of only 1680 - 4600 K through
 ISOCAM images. The excitation of these lines is expected to be purely
 collisional, meaning that the conditions in the emitting gas can be
 deduced conclusively, and an unequivocal decision between J shock
 models and C shock models is feasible.

 Continuum emission from hot dust (T about 1000 K) may, however,
 contribute significantly to the measured fluxes. Hardly anything is
 known about the occurrence and distribution of hot dust in outflows,
 yet the dust grains may play an important role in the reformation of
 molecules behind the shock fronts. So while we need to observe the
 emission from hot dust to discriminate between the line emission from
 H2 and the dust continuum, this offers the superb chance to study the
 occurrence and distribution of hot dust in the bipolar outflows from
 YSOs at no extra cost.