Modification, Characterization and Evaluation of a Quantum/Interband Cascade Laser Spectrometer for simultaneous airborne in situ observation of CH&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;, C&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;H&amp;lt;sub&amp;gt;6&amp;lt;/sub&amp;gt;, CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;, CO and N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O