If you have Latitude and longitude in your ASCII file you can convert your data in to raster format easily using ArcGIS software. You can convert your ASCII file in to column and row of an excel data. Then read this excel file into ArcGIS directly. Save the file in to .shp and convert this into raster using ArcGIS option "point to Raster. You will be able to generate you raster file. Else you can go through ENVI software where ASCII can directly be read and converted into raster group file.
Hope you will get benefited. You and most welcome for further discussion.