April 2, 2015

SCARAB images after geometry correction

SCARAB images after geometry correction (level 1A processing)

SCARAB instrument raw data have been processed, with CNES tools, on one orbit (orbit N° 695) to generate an example of level 1 product.

Here is the track on the Earth of the orbit 695:

Here are the 5 images generated by the level 1A processing:

Channel 1:

This channel is a visible channel, on a narrow band from 0.5 µm to 0.7 µm. It essentially allows the comparision with other images from other satellites, because this spectral band is often used. It also serves to determine the context of the measurement. From left to right, one can see:

the Middle-East, the Arabian sea,
a depression on the Arabian sea. This depression is very bright (white) because clouds reflect a lot of the Sun light.
India,
Malaya which disapears under clouds,
a night zone,
Africa, the Red sea, and again the Middle-East.

Channel 2:

This channel is a scientific channel. It detects all the light reflected by the Earth and the atmosphere in the short wave domain, meanning from 0.2 µm to 5 µm.

It is thus "visually" very near channel 1, but it contains precise radiometric data which will enable to get the radiative budget of the Earth.

Channel 3:

This channel is a scientific channel. It detects all the light reflected or emitted by the Earth and the atmosphere in the short wave and the long wave domains, meanning from 0.2 µm to 200 µm.

By substracting the channel 2 to channel 3, the energy radiated by the Earth can be obtained in the 5 µm - 200 µm domain, meanning the thermal domain. These data will enable to get the radiative budget of the Earth.

Contrary to channels 1&2, which are in the short wave domain, this channel detects a thermal signal during nights.

Channel 4:

This channel is a thermal channel, it detects the radiated energy in the 10-13 µm domain. It enables to correct the channel 5 synthetic image and gives an information near the temperature of the targeted zone.

One can see that the Arabian sea depression, very bright in channels 1&2, is very dark in channel 4. This color corresponds to a very cold temperature.

Channel 5:

This channel is a synthetic channel, obtained by substraction of channels 3&2. It represents the radiated energy in the thermal domain, from 5 to 200 µm.