This lesson is a case study of atmospheric ozone levels developed from observations over Thule, Greenland in 2002. Students will download a composite graph of this stratospheric ozone data taken from two different sources: the SAGE III satellite and an ozone sensor on a weather balloon. Instructions for downloading the graph to either a computer or a graphing calculator (the TI-84 Silver Plus is recommended) are included in the lesson. Students will then compare and analyze the two data sets shown on the graph. Emphasis is placed on the applicability of using the weather balloon data to validate the satellite data. This lesson uses student- and citizen science-friendly microsets of authentic NASA Earth system science data from the MY NASA DATA project. It also includes related links, extensions, and an online glossary.