There is two formats for data files: v1.0 File Format and ES File Format. ES (Extended Storage) is a RAM filesystem in HITACHI SR8000 system, and the ES File Format is used only in that machine.
A NuSDaS data file of v1.0 format is a sequence of records. Each record has a common structure shown in Table 1 (v1.0 Record Format Tables). All fields noted as 'integer' is written in the big-endian byte order. Note that it is similar but DIFFERENT *1 to sequential unformatted file of Fortran.
Possible value of the 'kind of record' field is as follows:
Record of this kind is the first mandatory record of data file. It contains metadata for system administration purpose. Payload of v1.0 NUSD record is described in Table 2.
Record of this kind is the second mandatory record of data file. It contains metadata commonly defined for all NuSDaS datasets such as identification (data type and base time), internal structure (list of member, valid time, plane and element), and grid/geometry structure. Payload of v1.0 CNTL record is described in Table 3.
Record of this kind is the third mandatory record of data file. The payload of the record is an array of 32bit integer, which can be interpreted as byte position of DATA records. Indices of the array is member, valid time, plane, and element: i-th (for simplicity, let us use C style index starting with 0) element of it gives position of a DATA record for e-th element, p-th plane, v-th valid time and m-th member; where i = (e + E * (p + P * (v + V * m))), E the total number of elements, P the total number of planes, and V the total number of valid times.
Record of this kind is optional: there may be no SUBC record, or even many SUBC records. They contains various metadata including vertical grid information, time integration span, and radar operation status. Format of the record is determined by a 4-character field (called 'group name') at byte offset 16. See v1.0 SUBC record for detail of SUBC records.
Record of this kind is optional: there may be no INFO record, or even many INFO records. They contains user-defined metadata. Four bytes from byte offset 16 in the record is called 'group name' and reserved for classification of INFO records. The rest of the record is not defined.
These records contain two-dimensional array data. Eight byte characters from byte offset 56 specifies encoding scheme. See v1.0 DATA record for detail of DATA records.
Record of this kind is the last mandatory record of data file. See v1.0 END record for detail.
ES is a memory-based filesystem of HITACHI SR8000. Since it has special I/O interface, the NuSDaS interface had to support it separately. The file format for ES is largely different. It is direct access file including fixed length records, and has no NUSD, INDX, nor END records. Just one SUBC and one INFO must exist at the beginning of file.
I am not sure about ES for further detail.
*1In NuSDaS, the size of record size fields (4 + 4 = 8 bytes) is
INCLUDED in the record size itself,
while is is NOT INCLUDED in Fortran files.
It may be changed in future versions.
Also note that the Fortran file format is usually written in the native
byte order of creating computer.