SPIRE spectroscopy of the prototypical Orion Bar photodissociation region

Aims. We present observations of the Orion Bar photodissociation region (PDR) obtained with the SPIRE instrument on-board Herschel. Methods. We obtained SPIRE Fourier-transform spectrometer (FTS) sparse sampled maps of the Orion bar. Results. The FTS wavelength coverage and sensitivity allow us to detect a wealth of rotational lines of CO (and its isotopologues), fine structure lines of C and N+, and emission lines from radicals and molecules such as CH+, CH, H2O or H2S. For species detected from the ground, our estimates of the column densities agree with previously published values. The comparison between (CO)-C-12 and (CO)-C-13 maps shows particularly the effects of optical depth and excitation in the molecular cloud. The distribution of the (CO)-C-12 and (CO)-C-13 lines with upper energy levels indicates the presence of warm (similar to 100-150 K) CO. This warm CO component is a significant fraction of the total molecular gas, confirming previous ground based studies.