Hi,
The mosaic images are defined by expressions where multiple bands can be referenced. That’s why the wavelength is no preserved in the output. You can set it manually when you right click on the band and selected properties. There you can enter the wavelength.
If you want to do this operational or on multiple products you can use gpt and the BandMaths operator.
You can use it to copy the bands and set the wavelength.
We have already an issue for this. [SNAP-745] Band properties in mosaic - JIRA (atlassian.net)
See also: