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==> In this proposal, more time is being requested for AFUENTE.PDR01
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We propose to observe a sample of high excitation molecular
lines in two selected positions of the photon-dominated region (PDR)
associated with NGC 7023. NGC 7023 is a prototypical reflection nebula (RN),
and the already existing single-dish and interferometric ground based
observations, show that it is one of the best objects to study the physical
and chemical structure of PDRs. Most of the projects on PDRs are centered
on the PDRs formed at the edges of HII regions. The results found in
these PDRs cannot be extrapolated to the PDRs associated  with RNe.
RNe are illuminated by intermediate mass stars and the spectrum  and
intensity of the incident UV field, as well as the gas physical conditions
are different. Since the birth rate for intermediate mass stars  is much
larger than for massive O stars, the study of the PDRs associated with
them is of major importance for the understanding of the  galactic
and extragalactic interstellar medium. In the first Call For Proposals
we got time to observe the infrared rotational lines of H2, CO, OH, CH, CH2,
HeH+ and NH3 toward four selected positions. Our goal was to  estimate
the abundances of these molecules, determine the physical conditions
of the hot molecular gas, and understand the cooling mechanisms across the
PDR. However, the time estimates given by the first LWS Time Estimator
happened to be severely wrong, and we can only observe two of them within
the time allocated for this project. With only two positions, we are unable
to achieve our objectives. Therefore, we propose to complete our observations
with two positions more.