The excitement was palpable as we waited to determine when Voyager 2 would reach the boundary of Neptune’s influence in the solar wind. To keep things interesting, we organized a prediction pool among the science teams at the Jet Propulsion Laboratory. A chalkboard was used to list the entries, with the predictions based on when the spacecraft would encounter the “bow shock” of Neptune’s magnetosphere in PDT-ERT (Pacific Daylight Time-Earth Received Time).
There were only five predictions to choose from, starting on Day of Year 235, which corresponds to August 23rd in non-leap years. The one-way light time from the spacecraft was 4 hours and 6 minutes, and the spacecraft event time (SCET) was typically given in Greenwich Mean Time (GMT). To convert from PDT-ERT to GMT-SCET, 7 hours needed to be added to get to GMT, followed by a subtraction of 4 hours and 6 minutes to adjust for the event occurring on the spacecraft earlier. This resulted in a 2-hour and 54-minute difference.
I predicted that Voyager 2 would reach Neptune’s boundary on DOY 236 at noon PST, which is equivalent to August 24th at approximately 8:00 pm GMT-SCET. However, much to my surprise, I was off by just over an hour as Voyager crossed into Neptune’s influence at around midnight EST on August 23rd, or roughly midnight GMT-SCET. Despite my slight error in prediction, it was still an exciting moment for us all as we witnessed Voyager’s journey into new territory.
