A compact, lightweight multichannel laser and heterodyne spectrometer is under development for the ExoMars-2018 landng platform. The instrument is aimed at sensitive measurements of the ambient atmosphere composition, isotopic ratios and structure, both in situ and on the open path by direct Sun observations. Begin the abstract two lines below author names and addresses. The abstract summarizes key findings in the paper. It is a paragraph of 250 words or less. For the keywords, select up to 8 key terms for a search on your manuscript's subject.