The Measurement of Air Pollution from Satellites (MAPS) instrument, flown on four Shuttle flights in 1981, 1984 and 1994 and is a precursor to EOS-era instruments. The main pollutant measured was carbon monoxide (CO). 

Mission Objectives

The objectives of the MAPS instrument were to measure the global distribution of CO in the troposphere and its role in global tropospheric chemistry.

Technical Specifications

The MAPS instrument was able to detect CO and nitrous oxide using gas filter radiometry to measure the IR absorption wavelength band in the atmosphere for these trace gases (4.67 micrometer). The instrument viewed the Earth simultaneously through three cells:

• One cell filled with CO
• One filled with nitrous oxide
• One filled with helium (which does not absorb at these wavelengths)

The difference in the energy received as seen through cell pairs enabled researchers to derive the amount of CO and nitrous oxide in the atmosphere. The nitrous oxide measurements provided a method for automatically rejecting cloud-contaminated observations of CO.

Instrument Components

The MAPS instrument consisted of four main subassemblies:

• The optical subassembly, which contained the optical elements, blackbodies, gas cells, detectors, preamplifiers, and calibration unit
• The electronics subassembly, which housed the signal processing and control circuits
• The flight tape recorder subassembly
• The aerial camera subassembly, which provided correlative cloud cover photos during the daylight portion of the flight