MODIS: Moderate Resolution Imaging Spectroradiometer [Satellite]

Aqua Satellite

What is MODIS Satellite?

Despite popular belief that MODIS is a satellite, it’s actually an instrument on-board a satellite.

MODIS stands for Moderate Resolution Imaging Spectroradiometer. It has 36 spectral bands, 250-1000 meter resolution and averages 2-day revisit period.

Because of this versatility, MODIS has changed how we understand our land, ocean and atmosphere. And due to its enormous coverage, it enables us to monitor activities such as active fires, land use change and volcanic activity.

Let’s dive right in and explore MODIS bands, resolution and temporal frequency.

MODIS Uses and Applications

Since its launch, MODIS had been referred to as the quintessential instrument of Earth Observation. This is because it covers more ground, captures more spectral bands with higher temporal frequency.

For example, it collects essential data about land, ocean and atmosphere about every 2 days. In these 3 examples below, we just barely scratch the surface of the applications and uses of MODIS imagery.

Fire and Hot Spot Detection

Active Forest Fires

The fire detection algorithm uses MODIS to detect active fires. By comparing temperature to neighboring pixels, it determines the severity and extent of the fire. If the difference is over a given threshold, it confirms the “hot spot” as an active fire. But if the fire is too small to detect due to the spatial resolution of the sensor, the satellite cannot detect it.

Land Cover

The MODIS instrument tracks land use change by examining is spectral properties over the land. For example, the 500-meter MODIS Land Cover Maps (17 land cover classes) describes the dominant class based on a 10 year span (2001-2010). Additionally, there is a 23-class ESA global land cover product available at 1km resolution.

Cloud Properties

Clouds are fundamentally important in weather and climate. Before MODIS, it was common to believe that clouds covered about 50% of Earth at any given time. But after examining MODIS imagery, it showed that cloud cover was closer to 70%. In addition, MODIS accounts for temperature and height of clouds as well as composition of ice or water.

READ MORE: 100 Earth Shattering Remote Sensing Applications & Uses

MODIS Imagery and Resolution

Spectral Resolution

MODIS is one of the most versatile sensors with its 36 channel imaging spectrometer. For the first 20 bands, it captures reflected solar radiation. From these bands, we can better understand the physical properties of the environment. For example, we use its 16 thermal bands to measure surface and ocean temperature.

Spatial Resolution

MODIS has a pixel resolution of 250m, 500m to 1 km. Starting with its finest spatial resolution, it can make out features about the size of 3 football fields. But its most important asset is its enormous swath covering a width of 2,330 km at 12-bit radiometric sensitivity.

Temporal Resolution

NASA Worldview
On-board NASA’s flagship satellites Terra and Aqua (A-Train), MODIS has a 2-day repeat coverage of the entire planet. Depending on cloud coverage, it’s temporal frequency makes this sensor a perfect candidate for monitoring any activity on land. MODIS sensors only capture data on the dayside portion because it measures reflected light from the sun. In a polar orbit, the Aqua satellite circles the Earth every 99 minutes.

Reflective Bands

Here is a list of all bands for the MODIS sensor including ground sampling distance and spectral bands.

Band Bandwidth (µm) Resolution (m) Application
1 0.620-0.670 250 Land cover
2 0.841-0.876 250 Vegetation
3 0.459-0.479 500 Soil Properties
4 0.545-0.565 500 Greeness
5 1.230-1.250 500 Leaf Index
6 1.628-1.652 500 Snow/Cloud Properties
7 2.105-2.155 500
8 0.405-0.420 1000 Ocean Biology and Color, Phytoplankton
9 0.438-0.448 1000
10 0.483-0.493 1000
11 0.526-0.536 1000
12 0.546-0.556 1000
13 0.662-0.672 1000
14 0.673-0.683 1000
15 0.743-0.753 1000
16 0.862-0.877 1000
17 0.890-0.920 1000 Water Vapor
18 0.931-0.941 1000
19 0.915-0.965 1000

Thermal Bands

Band Bandwidth (µm) Resolution (m) Application
20 3.660-3.840 1000 Forest Fires, Surface/Cloud Temperature
21 3.929-3.989 1000
22 3.929-3.989 1000
23 4.020-4.080 1000
24 4.433-4.498 1000 Atmosphere Temperature
25 4.482-4.549 1000
26 1.360-1.390 1000 Cirrus Clouds
27 6.538-6.895 1000 Water Vapor
28 7.175-7.475 1000
29 8.400-8.700 1000
30 9.580-9.880 1000 Ozone
31 10.780-11.280 1000 Surface/Cloud Temperature
32 11.770-12.270 1000
33 13.185-13.485 1000 Cloud Top Altitude
34 13.485-13.758 1000
35 13.785-14.085 1000
36 14.085-14.385 1000

Conclusion

Today you’ve learned that MODIS is an instrument on-board both the Terra and Aqua satellites. Over time, it has become pivotal in improving our understanding of our land, ocean and atmosphere.

For example, it gives us a peek inside the ocean and broadens our understanding of its biology and food cycle.

In the atmosphere, it helps us get the whole picture of cloud properties and what percent they cover Earth. Lastly, it assists us in monitoring active wildfires, land use change and volcanic activity.

Can you think of any other applications how scientists are using the MODIS instrument? Please let us know with a comment below.

MODIS Bands

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