Earth’s Flagship: Terra

Have you ever stopped to wonder what exactly NASA is? Sure, they have sent probes to investigate other planets, but NASA is also partly responsible for designing technology that gives us information about our very own planet. Some of that technology includes satellites such as Terra, the flagship of the Earth Observing System (EOS).  Launched on December 18, 1999, Terra is 6.8 meters long, 3.5 meters wide and weighs 11,442 pounds1—basically the size of a small school bus! If that isn’t impressive enough, the satellite orbits north to south every 99 minutes at an altitude of 705 kilometers above the Earth’s surface1. The satellite’s one simple mission: to help scientists better understand pollution and how it spreads throughout the globe. Using data collected daily, Terra examines atmospheric trends, such as global carbon monoxide spread, and what it could mean for the future of our earth.

The satellite itself has five sensors, each dedicated to specific monitoring tasks.  

  1. ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) gathers high resolution images in a wide range of electromagnetic spectrums.1
  2. CERES (Clouds and the Earth’s Radiant Energy System) measures the Earth’s total radiation budget, thus enabling scientists to assess clouds’ roles in radiative fluxes.1
  3. MISR (Multi-angle Imaging SpectroRadiometer) inspects clouds from different angles.1
  4. MODIS (Moderate-resolution Imaging Spectroradiometer) measures the properties of clouds, among other tasks.1
  5. MOPITT (Measures of Pollution in the Troposphere) helps us better understand the lower atmosphere and how it interacts with the land and ocean biospheres.1


MOPITT’s specific focus is the sources, transport and distribution of carbon monoxide in the troposphere, the lowest region of our atmosphere. It is also the first satellite sensor to use gas correlation spectroscopy, meaning the sensor measures emitted and reflected light from the Earth in three spectral bands.1As this light enters the sensor, it passes along two different paths containing carbon monoxide, which absorb different amounts of energy.  The small differences in the resulting signals correlate with the presence of carbon monoxide and other gases in the atmosphere.  

Carbon monoxide (CO) is not a particularly powerful greenhouse gas, but when elevated levels are present in the atmosphere it reacts with other air particles to create hazardous ground level ozone. If the CO levels are left untreated, many health hazards can arise due to the fact that large amounts of CO are toxic to blood-bearing creatures. Some of these health hazards include irritation of respiratory system, increased asthma, allergies that seem to persist and lung inflammation. MOPITT aims to better understand the patterns of these gases, and help mitigate or reverse the effects.1

With the help of other sensors, MOPITT has made it possible to track pollution plumes as they are transported across the ocean and land, allowing us to observe numerous plumes worldwide and their effect. The findings show that air pollution is a global issue, since the atmosphere does not respect international borders, thus meaning that pollution and air quality initiatives will require international cooperation. Through Terra, we aim to better understand our green planet and hopefully keep it green for centuries to come.   


(Image source:

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