some other errors: 1) <variableAgg name="dsp_band_1" /> names the field you want to aggregate 2) coordValue="1999-01-01T08:24:17Z", not coord="1999-01-01T08:24:17Z" <catalog xmlns="http://www.unidata.ucar.edu/namespaces/thredds/InvCatalog/v1.0" xmlns:xlink="http://www.w3.org/1999/xlink" name="URI-THREDDS OPeNDAP Data Server" version="1.0.1"> <service name="opendap" serviceType="OPENDAP" base="/thredds/dodsC/" /> <dataset name="Pathfinder AVHRR Northwest Atlantic Aggregation (6km Declouded)" urlPath="AVHRRAggregation.nc" ID="AVHRRAggregation"> <serviceName>opendap</serviceName> <netcdf xmlns="http://www.unidata.ucar.edu/namespaces/netcdf/ncml-2.2"> <dimension name="time" length="0"/> <variable name="time" type="String" shape="time" > <attribute name="_CoordinateAxisType" value="Time" /> </variable> <aggregation dimName="time" type="joinNew"> <variableAgg name="dsp_band_1" /> <netcdf location="http://dods.gso.uri.edu/dods-3.4/nph-dods/Pathfinder/Northwest_Atlantic/6km/declouded/1999/1/f99001082417.hdf" coordValue="1999-01-01T08:24:17Z" /> <netcdf location="http://dods.gso.uri.edu/dods-3.4/nph-dods/Pathfinder/Northwest_Atlantic/6km/declouded/1999/1/f99001181038.hdf" coordValue="1999-01-01T18:10:38Z" /> <netcdf location="http://dods.gso.uri.edu/dods-3.4/nph-dods/Pathfinder/Northwest_Atlantic/6km/declouded/1999/1/f99001195049.hdf" coordValue="1999-01-01T19:50:49Z" /> <netcdf location="http://dods.gso.uri.edu/dods-3.4/nph-dods/Pathfinder/Northwest_Atlantic/6km/declouded/1999/1/f99002081244.hdf" coordValue="1999-01-02T08:12:44Z" /> </aggregation> </netcdf> </dataset> </catalog>