Your organization may have a collection of aerial photography from three years, such as 1995, 2005, and 2008 and you want to publish these as a web service. These may have different resolutions, such as 1 meter, 2 feet, and 0.5 feet. The earliest collection could be a panchromatic in a Geographic projection and the other two are color in a UTM projection.
The best way to manage this data is as separate source Mosaic Datasets and Derived Mosaic Datasets in a Geodatabase. Using source and derived Mosaic Datasets generally makes the management easier while maintaining best performance.
Step1, create three source Mosaic Datasets with the Create Mosaic Dataset tool. Allow the software to automatically calculate band and bit depths when the data is added. The result will be a 1-band Mosaic and two 3-band Mosaic datasets. Add your imagery with the Add Rasters to Mosaic Dataset tool. You want to build separate overviews so users can view one dataset separately from another at all scales. Use the Build Overviews tool to do this. Modify the attribute table for each by adding a text field for the Year and populate the field with the year.
Step 2, create one Derived Mosaic dataset containing three bands. This is done using the Create Mosaic Dataset tool. This one Mosaic dataset will be used to provide the best color imagery combination. Then add the three source Mosaic Datasets to it using the Table raster type in the Add Rasters to Mosaic Dataset tool. The Table Raster type is very important as it reads all the records from the source Mosaics and populates them in the Derrived Mosaic. If your change the source Mosaic then you can use the Synchronise Mosaic Dataset tool to update the Derrived Mosaic.
You do not build overviews on this Mosaic Dataset as they are built for the source Mosaic Dataset. As you want to view the imagery by year you will need to modify the default mosaic method to be By Attribute and specify the default year, such as 3000 to display using the latest imagery.
Step 3, create a Reference Mosaic dataset to publish the contents of the Derived Mosaic Dataset. This is done using the Create Referenced Mosaic tool. As before you need to update the default mosaic method again to be By Attribute. You now publish this Mosaic as an Image Service with the Image Extension for ArcGIS Server. Users can now either access the Referenced Mosaic Directly or via the Published Image Service.