The Common Data Format (CDF) is developed by NASA's Space Physics Data Facility (SPDF) for time-series and multi-dimensional scientific data from space missions.

Transparent Access: Read CDF files with nc_open() and standard NetCDF functions — no explicit initialization call needed when using .ncrc autoload.

Type Mapping:

CDF_INT4 → NC_INT
CDF_REAL8 → NC_DOUBLE
CDF_TIME_TT2000 → NC_INT64

Attribute Conventions: CDF FILLVAL attributes are automatically renamed to _FillValue.

Note: CDF moved from UDF2 to UDF4 in v2.2.0, eliminating the former mutual-exclusivity with GRIB2.

Use Cases: NASA IMAP, MMS, Van Allen Probes, and other space physics mission data.

Enabling:

cmake -B build -DNEP_ENABLE_CDF=ON # CMake

./configure --enable-cdf # Autotools

Dependencies: NASA CDF library v3.9.x — download from https://spdf.gsfc.nasa.gov/pub/software/cdf/dist/latest/ or spack install cdf.

Resources: NASA CDF Homepage · CDF C Reference Manual

Example:

nc_open("data.cdf", NC_NOWRITE, &ncid);
nc_inq_varid(ncid, "Epoch", &varid);
nc_get_var_longlong(ncid, varid, epoch_data);
nc_close(ncid);