Volume 14, Number 3, September 1998
By Joseph King
At the request of NASA's chief information officer, NSSDC has generated a white paper to be used as the basis for a new science data retention policy of NASA.
Among the chief tenets of the paper is that for each data-generating NASA science investigation there is a definitive data set containing all the science potential of the investigation, and this data set needs to be held within NASA indefinitely. This data set, not yet irreversibly transformed, is often called level 1A in some circles. It either contains or is accompanied by all the supporting material (documentation, calibration files, software, etc.) needed to make the data correctly and independently usable.
To ensure long-term preservation and usability, data sets and sometimes their supporting material need to be transformed, sometimes simply by transcribing bit patterns to new media but sometimes by software modifications or other more expensive transformations. In rare cases the relevant NASA associate administrator may certify that data sets are not appropriate for expensive lifetime-extending transformations if the anticipated future use of the data is too low.
Data sets from an investigation that are earlier than the definitive data set in the processing cycle (for example, the raw telemetry data) may be released after sufficient testing shows that definitive data sets faithfully reproduce the content of the earlier data sets.
Data sets derived from the definitive data sets may be archived indefinitely or may be recreated on demand from the definitive data sets. Which course an archive follows is based on the cost effectiveness of the two approaches; this will depend on, among other things, the nature and volume of the derived data and the anticipated frequency of demand for the data.
A small subset of the data to be retained indefinitely within NASA archives will be designated as permanently important from an historic perspective for the nation's life. A copy of this small subset will be made and transferred to the National Archives and Records Administration for its permanent retention.