Normally, MDRs are seen to be of little use once the relevant information is extracted from them. Scientific measurements
are extracted, packaged in the appropriate form, and sent to the corresponding experimenters for further processing and
evaluation. Engineering telemetry is used by the spacecraft operations team to control and guide the spacecraft. MDRs are not
necessarily considered worth preserving once the scientific data has been extracted, and the engineering telemetry is no longer
needed for spacecraft operations. Indeed, the MDR retention schedule prescribed that the tapes be destroyed after 7 years.
Fortunately, most of the MDRs for the Pioneer 10 and 11 projects have been preserved nevertheless (see discussion in [397
]).