This paper provides the rationale, objectives, approach, and a brief description of the instrumentation included in the second airborne Chemical Instrumentation Test and Evaluation (CITE 2) mission conducted by NASA. This mission, conducted on NASA's Electra aircraft, was based at Moffett Field, California, and intercompared data from instruments measuring NO2, HNO3, and PAN in the troposphere. Ancillary measurements augmented the intercomparison data in order to address specific questions related to the budged and partitioning of odd nitrogen species in the troposphere. This study, conducted in August 1986, encountered marine and continental air with free tropospheric mixing ratios of NO2, HNO3, and PAN typically less than 120, 150, and 200 parts per trillion by volume, respectively. Other papers in this issue provide the detailed results of the intercomparison tests and also discuss issues related to the budget and distribution of odd nitrogen species in the troposphere.