Available with Spatial Analyst license.
Overview
Generates a reducedresolution version of a raster.
Notes
Depending on the value specified for the cell factor (whether the division of the cell factor by the number of cells in a row or column leaves a remainder), the spatial extent of the input cells will not cover the same extent for the last cell in a row or column as the output raster.
Parameters
Parameter  Description 

Raster (Required)  The input raster to be aggregated. 
Cell Factor  The factor by which to multiply the cell size of the input raster. For example, a cell factor value of three would result in an output cell size three times larger than that of the input raster. 
Aggregation Technique 
The method used for aggregation. The values of the input cells encompassed by the coarser output cells are aggregated by one of the following statistics:  Sum—The total of the input cells. This is the default.
 Maximum—The largest value of the input cells.
 Mean—The average value of the input cells.
 Median—The median value of the input cells.
 Minimum—The smallest value of the input cells.

Expand extent if needed  Defines how to handle the boundaries of the input raster when its rows or columns are not a multiple of the cell factor.  Checked—Expands the top or right boundaries of the input raster so the total number of cells in a row or column is a multiple of the cell factor. With this option, the output raster can cover a larger spatial extent than the input raster. This is the default.
 Unchecked—Reduces the number of rows or columns in the output raster. This truncates the remaining cells on the top or right boundaries of the input raster, making the number of rows or columns in the input raster a multiple of the cell factor. With this option, the output raster can cover a smaller spatial extent than the input raster.

Ignore NoData in calculations  Denotes whether NoData values are ignored by the aggregation calculation.  Checked—Specifies that if NoData values exist for any of the cells that fall within the spatial extent of a larger cell on the output raster, the NoData values will be ignored when determining the value for output cell locations. Only input cells within the extent of the output cell that have data values will be used in determining the value of the output cell. This is the default.
 Unchecked—Specifies that if any cell that falls within the spatial extent of a larger cell on the output raster has a value of NoData, the value for that output cell location will be NoData. When the this option is used, it is implied that when cells within an aggregation contain the NoData value, there is insufficient information to perform the specified calculations necessary to determine an output value.

Feedback on this topic?