ImgSPEC was designed specially for the imaging spectroscopy use case. While the design and interfaces for accessing and working with the data are specific to imaging spectroscopy, any data can be used uploaded by the user or via a drop down search for other NASA data.
What is Imaging Spectroscopy?
Imaging Spectroscopy is a powerful technology that measures the full electromagnetic spectrum of light from 400 to 2500 nm. This is unique from multi-spectral data from a camera or even Landsat/MODIS satellites because the features of these spectra indicate the presence of different materials, allowing us to precisely measure the chemical and physical composition of the objects in the image.
Figure modified from image courtesy of Rob Green, Jet Propulsion Laboratory, California Institute of Technology.
How does it work?
Each chemical compound has a unique structure. Many of these structures absorb and reflect visible and infrared light differently, imparting unique peaks and valleys in the distribution of light reaching the sensor. Because we know the unique signatures of many common materials, we can process these data to determine the amount of a particular material that is present. What materials or chemicals we can detect and how sensitive we are to their concentration depends on a number of factors related to how an image was collected.
What are the Data Products?
Through a series of processing steps that clean the data to account for different effects, we can identify the chemical fingerprint of the Earth’s surface and atmosphere. Each processing step is called a level, with the most raw and unprocessed step starting at Level 0.
Data Product Level | Product Short Name | Description |
0 | Digital Numbers (DN) | Photon count |
1 | Radiance | Photons reflected and absorbed in the atmosphere and the surface |
2 | Reflectance | Photons reflected off the surface |
2A | Topographic, Bi-directional Reflectance Corrected | Corrections to normalize an image to compare one place to another independent of the surface texture, sensor view angle, and sun angle. |
2B | Functional Traits | Chemical concentrations and structure attributes of the surface |
2C | Fractional Cover | % of a pixel that represent a given land cover, which has a unique signature of functional traits |
For what is it used?
Imaging spectroscopy data can be used in a range of disciplines including:
- Hydrological Cycles, Water Resources and Aquatic Ecosystems
- Weather and Air Quality
- Terrestrial Ecosystems and Natural Resource Management
- Climate variability and Change
- Earth Surface/ Geology
These data are useful for not only research, but also providing decision support for every-day decision making including fire response and mitigation, agriculture, and so much more! For example, imaging spectroscopy data that can differentiate functional traits of the surface can be used to make maps of biodiversity used in conservation planning. Maps of fractional cover of green vegetation and non-photosynthetic (dead/dormant) vegetation can tell us how stressed the landscape is and how flammable it is.