NASA - National Aeronautics and Space Administration

Description

This document describes the file naming convention used by the ESPO data archive for Ames-format files. The Ames file name conventions were originally developed in 1987, when file names could be at most 12 characters in length. In 1998 Ames File Format version 2.0 was introduced, allowing longer file names (up to 30 characters in length), but because the changes aimed to be backwards-compatible, typical Ames-format file names have remained 12 characters in length.

The structure of a typical Ames-format file name is:
CCyyyyMMdd.ext
Where CC is a two-letter file code, yyyyMMdd is the date, and .ext is an extension, typically providing the aircraft used for the measurements. The full representation of an Ames-format file name is:
CCyyyyMMdd[_[hh[mm[ss]]][_c][_Rn][_Ln][_Vn]].ext
The square brackets [ ] enclose optional parameters. The remainder of this document explains the components of this file name.

Character Set

File names must conform to the ISO 9660 file name convention. This convention permits the full file name (including extension) to be at most 30 characters in length. The only characters that can appear in the file name are:
0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ_.
Notice that the alphabetic characters are upper case. Files can be submitted to the archive using lower-case alphabetic characters, but the names will automatically be capitalized as part of the upload process. Only one period (.) can appear in the file name, namely at the start of the file name extension.

File Name Components

CC

represents a two-character prefix for the file name (0-9, A-Z). Ideally, this will be a mnemonic code for the measurement, instrument, or subject of the file. If more than two characters are necessary to create a unique file code, component c (see below) can be used to expand the length of the file code.

yyyy

represents four digits specifying year (i.e. 1997, 2011, etc.).

MM

represents two digits specifying month number (01-12).

dd

represents two digits specifying day number (01-31).

hh

represents an optional two digits which specify an hour(00-23).

mm

represents an optional two digits which specify minutes (00-59).

ss

represents an optional two digits which specify seconds (00-59).

c

represents an optional identifier for a particular type of file, where c can be one or more characters (letters, numbers, or underscores). c is used whenever CC (above) is not sufficient to provide a unique file name. There are some restrictions on the allowed values of c, necessary to ensure that c can not be confused with other components of the filename. For example, R2 or L0 are not allowed because they are too similar to possible revision numbers or launch counters.

Rn

represents the revision number for this file. The first revision of a given file that is uploaded to the archive is assigned revision R0; the revision number increases for each time a new version of that file is uploaded to the archive. Note: Rn was not part of the Ames file format prior to version 2.1 of the format specifications. By default, Ames-format file names in the ESPO data archive do not contain revision numbers, although as of September 2011 the revisions are tracked for all archive files.

Ln

represents an aircraft launch counter. When the contents of a file pertain to a second or third aircraft launch on the indicated date then use Ln to indicate the launch number (i.e. L2, L3, etc.). When this parameter is omitted from the file name then launch number one is implied.

Vn

represents a volume counter for a multi-volume set of files. This option is effectively obsolete, being a holdover from when files had to be split to fit onto floppy disks.

1. For ASCII data files, the volume number (the n in Vn) must match the volume number (IVOL) in the sixth line of the file header.
2. The number of digits used in each volume number must be the same (V1, V2, V3, ..., or V01, V02, V03, ..., etc.).
3. If Vn is omitted from the file name then volume number one of a one-volume file set is implied (the default).

ext

represents two or more characters to identify the measurement platform, source, or association of the data (for data files), or image file type (for image files).

Notes

1. Dates and times in file names are always UTC.
2. In general, the date and time in the file name give the date/time at which the data within the file begin (data files), or date/time at which the image applies (image files).
   • For aircraft data files, the date always refers to the UTC date of launch, and further specification of time in those file names is discouraged.
   • If multiple flights of the same aircraft occur on the same date, the aircraft launch counter (Ln) should be used to distinguish between the flights.
3. There can be two, four, or six digits following the first underscore, which represent the time as hh, hhmm, or hhmmss.
4. If a file name does not include a time but does include other optional parameters then the first of those parameters is separated from the date by two underscores, e.g., CCyyyyMMdd__Ln.ext.
5. File name codes are constructed from the constant parts of the file names and used as a shorthand way to reference a particular type of file. File name codes have one of the following forms (the date/time and Ln and Vn are variable parts of a file name):
   1. CC.ext
   2. CC__c.ext
6. For any given mission, each file name code must be unique, and therefore each file name will also be unique.
7. If two or more file codes use the same prefix CC and extension ext then all of those codes must also include a c identifier, and each CC__c.ext code must be unique.
   • Without this rule, an archive directory could include some AA.DC8 files and some AA__5HZ.DC8 files, and there would not be a simple way for users to list or download just the AA.DC8 files.
8. File catalogs (datatable.* and imagetable.*) are included in the docs directory of each archive account to link file name codes, and therefore file names, with the contents or subject of each type of file.

Examples

Some examples of file name codes, file names, and explanations of the meaning of the file names are given below to illustrate the construction of file codes and file names.