MODIS Terra

MODIS Terra Satellite System

Overview/History

MODIS stands for Moderate Resolution Imaging Spectroradiometer. MODIS is an important instrument that is aboard both Aqua and Terra Satellites. This instrument provides high radioactive sensitivity in 36 spectral bands. MODIS Terra was launched in 1999, and MODIS Aqua was launched in 2002. Both of these MODIS instruments provide an unprecedented look at our Earth’s phenomenology for a wide range of users.

Terra was the first Earth Observing System satellite to be launched in 1999. The goal of Terra is to understand the Earth’s changing climate and to explore the connections between atmosphere, ocean, land, and energy balance. Terra also provides data to analyze the impact of human activity and natural disasters on the Earth’s environment. The main question for the Terra mission is: How is Earth changing and what are the consequences for life on Earth?

Like other satellites, Terra has some specialized instruments onboard that allow for different types of data collection and analysis. The five instruments are: Advanced Spaceborne Thermal Emmission and Reflection Radiometer (ASTER), Clouds and the Earth’s Radiant Energy System (CERES), Multi-angle Imaging SpectroRadiometer (MISR), Moderate Resolution Imaging Spectroradiometer (MODIS), and Measurement of Pollution in the Troposphere (MOPITT). The Unites States is responsible for CERES, MISR, and MODIS, while Japan has ASTER and Canada has MOPITT.

Spatial/Spectral/Time Resolution

ASTER obtains high resolution images at a range of 15-90 square meters per pixel. It is known as the zoom lens for other Terra instruments. MODIS has a 2,330km wide viewing swath, which sees every point on Earth every 1-2 days. MOPITT’s spatial resolution is 22km at nadir with swaths that are 640km wide. Terra has a repeat cycle of 16 days, and orbits the Earth at 705km.

Pros

Terra’s instruments are effective in disaster assessment applications because of their fast processing and near real-time images. ASTER’s high resolution images are very useful in studying climate change and effects of natural disasters. MOPITT is valuable in measuring human-induced changes in the atmosphere such as carbon monoxide and other greenhouse gases.

Cons

Terra is now thirteen years old, which is relatively old for a satellite. Occasional malfunctions occur, resulting in loss of data and power outages to the state of the art instruments. Terra MODIS has data transmission problems at times, which takes the satellite offline until it is repaired. Like other satellites, Terra requires occasional maintenance and updates to function properly.

Examples of Use

The Environmental Protection Agency (EPA) uses data collected from MISR, MOPITT, and MODIS for air quality measurements. The Federal Aviation Administration (FAA) uses ASTER, MODIS, and MISR to monitor and measure volcanic eruptions and ash emissions. The US Forest Service relies on ASTER, MISR, and MODIS to monitor wildfires. The measurements taken by Terra’s instruments show how Earth’s surface is changing as a result of both short-term climate variability and climate change such as glaciers and melting ice sheets. The real time data that these instruments provide is very valuable for each of these agencies and organizations to monitor the Earth and its phenomena.