A Space Odyssey: How We Waited for Voyager 2 to Cross the Neptune Boundary and Documented Our Predictions

The anticipation was palpable as we eagerly awaited the moment when Voyager 2 would cross the boundary of Neptune’s influence in the solar wind. To keep things exciting, we organized a prediction pool among the science teams at the Jet Propulsion Laboratory. A chalkboard was used to list the entries, with 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, ranging from Day of Year 235, which corresponds to August 23rd in non-leap years, to Day of Year 236. 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 difference of 2 hours and 54 minutes.

My prediction was set for 12 noon on DOY 236, which was August 24th at 1454 GMT-SCET. The Plasma Science experiment actually detected the bow shock on August 24th at 1438, coming quite close to my guess. What truly stood out was the documentation of this prediction pool and the fact that a photo capturing the event still exists.