What is meaning of Emissive in ENVI?

Question

When I view MOD02 data in ENVI directly with ...
File--Open image file, ENVI automatically loads data.
So what is the meaning of Emissive?

The description of MOD02 data can be found in MOD 02 - Level-1B Calibrated Geolocation Data Set and MODIS Data Product Non-Technical Description - MOD 02, 03.

Answer 1

It has nothing to do with ENVI, the term 'emissive' is contained within the dataset (HDF file) and ENVI just uses the HDF subdataset info to generate band names.

The values are scaled radiance for the thermal bands (20-36). See the Level 1B Product User's Guide, section 5.5 "Technical Content of Thermal Emissive Band SDSs"

Answer 2

Simply speaking, emissivity is the amount of energy that is emitted by a body in form of radiation. See the wikipedia article for a proper definition.

Satellite instruments measure the emitted energy at a certain wavelength. These are subdivided to be sensitive to certain objects (on earth’s surface). See the MODIS wikipedia article for more information on the sensitivity of the different MODIS bands.

If this is still hard to understand for you, then I would recommend that you read through a basic text book on remote sensing or through tutorials in the internet. Here is a starter.

Answer 3

After going to the exact product you have defined in your question.
It looks as though you may be viewing the LADDS 1 km band 6. It states that the reflectance is determined for bands 1-19, 26 using the modis solar diffuser data modis data
In the product table the MOD 02 - Level-1B Calibrated Geolocation Data reflectance is determined Through knowledge of the solar irradiance (e.g., determined from MODIS solar-diffuser data, and from the target-illumination geometry).
The emissive library defines emissive values for different materials.

Free dictionary definition is ...

e·mis·sive adj. Having the power or tendency to emit matter or energy; emitting.