aareadme file at 
ftp/spacecraft_data/explorer/explorer35/plasma_probe/3-min_interplanetary_plasma_param/old/aareadme.txt
------------------------------------------------------------
This directory provides access to 1967 and 1968 files of
3-min plasma parameter data in ASCII format, from the MIT
Faraday Cup flown on Explorer 35.  There are in this directory
1967 and 1968 files of "Version 1" and "Version 2" data sets.  
Version 1 was created from the EBCDIC-format data originally 
provided by MIT, and Version 2 was used to create Version 3 
described at ftp/spacecraft_data/explorer/explorer35/
plasma_probe/3-min_interplanetary_plasma_param/aareadme.txt.
Versions 1, 2 and 3 are all ASCII and were all created in 2010 
by the Space Physics Data Facility (SPDF).

The main changes between the versions were:
0 -> 1.  Change format from EBCDIC to ASCII.
1 -> 2.  Change time tagging (MMDD>DOY), add spacecraft position data.
2 -> 3.  Delete flow velocity data that were not aberration-
corrected; delete engineering-oriented parameters; change 
flow angle sign conventions for consistency with other data; 
introduce Cartesian representation of flow velocity vector.

Version 1 files have names of the form
explorer35_3min_plasma1967_v1.asc,
while Version 2 files have names of the form
explorer35_3min_plasma1967_v2.txt.

Version 1 files are described in detail in file aareadme_v1.txt
of this directory, while Version 2 files are described in detail
in file aareadme_v2.txt