The HEOS-1 satellite has observed on day 84, 1969 a shock pair connected with a plasma bulk velocity increase from 400 had a Mach number of 1.7, the reverse shock had Mfast =1.4. The time interval between the two shocks was of 7 hours and 10 minutes. The time delay between HEOS-1 and Explorer 35 reverse shock observation (20±6 minutes) agrees with the computed time delay (11±4 minutes).