BS ISO 11104:2011 pdf free download – Space data and information transfer systems – Time code formats.
d) Subsets may NOT consist of partial subfields (e.g., must use ‘ss’, not ‘s’). In particular, consistent use of the complete four-character YYYY subfield is required (e.g., ‘1989’ instead of ‘89’) because of the need to accommodate the upcoming century rollover in only 11 years. It should be noted, however, that each fractional second (‘d’ character) is considered to be a complete subfield, and so any number of fractional seconds may be used.
e) If calendar and time SUBSETS are then brought together to form a single time code format (joined with the ‘T’ separator) the CALENDAR subset may NOT have been truncated from the RIGHT, and the TIME subset may NOT have been truncated from the LEFT. That is, the format must be integral around the ‘T’.
f) Standardization on the use of these time code formats for purposes OTHER than identifying an instant of calendar or time in UTC (e.g., unconventional use as a counter or tool for measuring arbitrary intervals) is not recommended. It is felt such a specialized application can best be viewed not as a time code format but rather as an engineering measurement format. Any such application of these time code formats is considered beyond the scope of this Recommended Standard.
3.5.2 P-FIELD
There is no P-field identifying the ASCII Time Code Formats. The P-field information is implicit in the parsing of the ASCII time code.
Instrument data acquired from spacecraft have little value unless it is possible to recreate the significant environment of the instrument during the measurement collection phase. Such ancillary data parameters as time, position, velocity, attitude, instrument temperature, concurrent ground truth measurements and many other parameters may be essential for the proper interpretation of the instrument data. Of these ancillary data parameters, the time of the instrument measurements is certainly the most vital parameter. The reasons for this are the following:
(I) In many cases, the instrument analysis can be based, nearly exclusively, on the sampled sensor time series.
(2) Time provides the most efficient and often the only possible linkage between instrument data and externally generated ancillary parameters. Two independent measurement processes, each correlated with time, can then be correlated with each other.
However, the resulting proliferation of slightly different codes is not desirable. The selection of one particular code will depend on the chosen optimization criteria in the given application. For example, table B-I compares the four Recommended codes in terms of the three selection criteria identified by the CCSDS.