Discover how radar satellites observe our changing Earth
Dancing with the SARs | THIS WEBSITE HAS BEEN CREATED BY SAJAN SARAVANAN
NISAR stands for NASA-ISRO Synthetic Aperture Radar. It is a joint Earth-observation satellite mission developed by NASA and ISRO.
NISAR studies Earth's land, ice, vegetation and other surfaces using radar technology.
Study flooded areas and changes in water-covered land.
Study forest structure and changes in vegetation.
Measure ground-surface movement using radar observations.
Study ice movement and changes in glaciers.
Observe changes in crops and agricultural landscapes.
Monitor wetlands and changing water conditions.
NISAR uses a technology called Synthetic Aperture Radar, commonly known as SAR.
Radar sends its own energy towards Earth and measures the returning signal.
Example: NISAR
Sensors measure naturally available energy, such as sunlight reflected from Earth's surface.
Example: Many optical satellite sensors
When NISAR sends microwave signals towards Earth, different surfaces scatter the radar energy in different ways. Scientists study the returning signal to understand the surface.
Smooth surfaces such as calm water often reflect radar energy away from the satellite. Therefore, they may appear dark in a radar image.
Forests and vegetation contain leaves, branches and stems. Radar signals can scatter between these different parts of the vegetation.
Radar energy can bounce between two surfaces, such as the ground and a vertical building wall or tree trunk. This can produce a strong return.
NISAR carries two radar systems that use different microwave wavelength ranges.
Frequency: Approximately 1.2 GHz
Wavelength: Approximately 24 cm
L-band has a relatively long wavelength. It is useful for studying vegetation, forests, soil and ground movement.
Frequency: Approximately 3.2 GHz
Wavelength: Approximately 9.4 cm
S-band has a shorter wavelength than L-band. It provides another view of Earth's surface and vegetation.
Polarisation describes the direction in which a radar wave is transmitted and the direction in which its returning signal is received.
There are four common polarisation combinations:
Click HH, HV, VH or VV to learn what each combination means.
The transmitted and received waves have the same polarisation.
HH VVThe transmitted and received waves have different polarisations.
HV VHRadar images are not ordinary photographs. They represent measurements of radar signals returned from Earth's surface.
In a grayscale image, different brightness levels represent different radar return strengths.
Dark pixels represent lower displayed intensity, while bright pixels represent higher displayed intensity.
Scientists can assign different radar measurements to red, green and blue display channels. This creates a false-colour composite.
The colours help highlight differences between measurements. They are not the actual colours of the land.
NISAR data is available in different products. Each product is designed for particular scientific uses.
Geocoded Covariance Matrix
GCOV provides map-projected radar measurements describing surface scattering and polarimetric information.
It can help scientists study vegetation, flooding, agricultural areas and surface changes.
Geocoded Unwrapped Interferogram
GUNW is an interferometric product made using radar observations from different acquisitions.
It can help scientists investigate ground movement and deformation.
Scientists can study changes by comparing observations collected at different times.
Radar observations can help map flooded areas, including during cloudy weather.
Radar measurements can help investigate forest structure and changes.
Interferometric radar techniques can reveal patterns of ground deformation.
Radar observations can help study crop growth and changing field conditions.
Satellite radar can help scientists study glacier and ice movement.
Radar can support monitoring of wetlands and changing water conditions.
Try these questions to check what you have learned.
What does SAR stand for?
Which radar band has the longer wavelength?
What does HH mean?
Which product is an interferometric product?
Does a dark pixel always mean water?
Use these resources to learn more about NISAR, radar remote sensing and satellite data.
NASA-ISRO NISAR Mission Website NASA Alaska Satellite Facility Data Search NISAR Data User Guide NASA Earthdata Search NASA Earthdata: What is Synthetic Aperture Radar? NASA Earthdata: What is Remote Sensing? NASA ARSET Training Resources NASA UAVSARDancing with the SARs is our student project that connects users with real NISAR observations.
Users can select a date, choose a location on the interactive map, and select GUNW or GCOV to search available observations.
Our goal is to make satellite radar data easier for students to explore and understand.
Visit the Image Explorer to search for NISAR observations from different locations.
→ Open NISAR Image Explorer