I have a looked through the spec and can’t see any reference to snow sensor texture. If I change from summer to winter I would need to update the FLIR image accordingly. Am I right in thinking it would involve more than just changing the material values, and a different sensor texture would be required?

1.  6.1.1.1 Visible Spectrum Terrain Imagery (VSTI) Components
The VSTI component provides the visible spectrum imagery that is orthographically draped over the terrain skin generated from Primary Terrain Elevation Dataset.  The CDB specification provides a flexible means to store and retrieve the VSTI components in accordance to time of year.  There are three ways to organize VSTI components of the Imagery Dataset:
1.  Yearly:  The first approach requires a single, year-round representation of the terrain imagery.
2.  Quarterly:  The second approach requires four variants of the terrain imagery, one per season.  In the case of a missing variant, simulator client-devices are required to select the closest variant (in-time).
3.  Monthly:  The third approach requires monthly-variants of the terrain imagery, one per month.  In the case of one or more missing variants, simulator client-devices are required to select the closest variant (in-time).

All three approaches can be stored individually or in combination within the CDB.

004 *.TIF,
*.JP2 Alternate VSTI
Winter representation Winter equivalent of above, i.e., this is the preferred Dataset Component for springtime representative terrain imagery.  Can be used interchangeably with all other Alternate VSTI representations.

Smiffy, as you pointed out, the CDB spec provides support for seasons by having different primary textures. In that case, you would search for files whose names look like D004_S002_T004 which is the code for Alternate VSTI Winter representation.

In the current version of the Specification, the raster material descriptor dataset (006_RMDescriptor) provides only one description of the composite material asssociated with the raster material texture (005_RMTexture).  Meaning you cannot change the material based on the time of the year.

Right now, we have been working on a proposed extension to the Composite Material Table described in section 2.5.2.2 to include alternate materials based on the time of the year… in a manner similar to alternate VSTI representations.

As a result, with version 3.0 of the Spec, a FLIR sensor would be provided with a winter texture (if available) to modulate a single set of raster materials for the terrain.

This may seem a limitation, but having implemented this functionality on our sensor channel, we (and the customer) found the result sufficient for its intended use and training purposes.

I hope this answers your question.