In the __[1]__ It Was Discovered Through ________[2]________ of the Atmosphere

In the __[1]__ it was discovered through ________[2]________ of the atmosphere that the ozone layer was being depleted at an alarming rate.
Answer 1 Choices:
1900s
1930s
1960s
1980s
2000s
Answer 2 Choices:
aerial photography
images taken by NASA's Total Ozone Mapping Spectrometer (TOMS)
remote sensing
satellite photography
satellite remote sensing