Looking now at Arctic Ocean coverage by the newly available ASTER imagery (green, red, near infrared; 15 m resolution 8-bit precision) at EarthExplorer, it is very similar to Landsat-8 in that satellite admin decided to
only keep near-coastal imagery in the belief no one is interested in images of sea ice. This could amount to shutting down acquisition, download, storage, or provisioning.
The first image shows recent swaths through the Beaufort Sea. There are some nice images of the Mackenzie delta, land-fast ice, and floes on the shelf. Coverage does not extend to very much of the Beaufort Gyre; for example, Big Block floe is well out of range (red star 73.3º, -147.3º).
The second image shows one of the outer floes at full resolution -- which reveals many tiny pieces of sea ice that would not be visible with Modis and are very unlikely to be used in calibrating extent, area, or volume products.
The small round 'blue' circle may be a melt pond. There is no way however to make 'natural color' since the satellite has no blue channel. It might be approximated by duplicated the green channel (which will be highly correlated) and discarding the infrared. The 4th image shows various channel combinations with the potential to resolve this.
The 3rd image below decomposes the colors of the supposed pond into their RGB channels. The 'red' channel seems to provide the most detail; it is probably band 1 (red wavelengths, second image). The 'green' channel then corresponds to band 2 green wavelengths and the blown-out contrast to band 3 infrared.
The interesting thing about ASTER is the 15m infrared channel. The nearest counterpart on Landsat-8 is the 30 m band 5 which is farther out in the infrared: 0.85–0.88 vs 0.76-0.86 µm. We have done very little on these forums with band 5. There is mass confusion over how to interpret anything not in the visible.
On ASTER, band 3 has both nadir and backward looking options, designated 3N or 3B. The purpose of 3B is unclear; it involves a time lag.
There's quite a good interactive applet tutorial on color mixing at the links below, helpful in understanding mixing of monitor color channels and human color perception. The ASTER infrared channel is somewhat outside the gamut of what the eye can see. The gaussian-type peaks represent the likelihood that a photon of the given wavelength will register with the sensor. That's most likely at the peak wavelength but falls off on the shoulders.
https://graphics.stanford.edu/courses/cs178-10/applets/colormatching.htmlhttps://graphics.stanford.edu/courses/cs178/applets/colormixing.htmlASTER images typically come in a HDF-EOS file format but can be converted to Geotiff files in several projections.Tools for carrying out data transformations can be found at
https://lpdaac.usgs.gov/tools. though this seems not to go anywhere useful to ordinary users.
Level 3 ASTER images classify each pixel of polar scenes into one of eight classes: water cloud, ice cloud, aerosol/dust, water, land, snow/ice, slush ice, and shadow. Sounds promising but where do we get them? EarthExplorer has only the DEM and L1T images.
http://wiki.landscapetoolbox.org/doku.php/remote_sensor_types:asterhttps://en.wikipedia.org/wiki/Advanced_Spaceborne_Thermal_Emission_and_Reflection_Radiometer