Exciting Voyager 2 Encounter: Prediction Pool and Unforgettable Photo Documentation

As we eagerly awaited the arrival of Voyager 2 at the boundary of Neptune’s influence in the solar wind, we decided to keep things exciting by organizing a prediction pool among the science teams at the Jet Propulsion Laboratory. We used a chalkboard to list our entries, based on when we thought the spacecraft would encounter the “bow shock” of Neptune’s magnetosphere in PDT-ERT (Pacific Daylight Time-Earth Received Time).

We had only five predictions to choose from, all falling on or around 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, we added 7 hours 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 noon on DOY 236, which was August 24th at 1454 GMT-SCET. Unfortunately, my guess was not quite right as the Plasma Science experiment detected the bow shock an hour later at 1438. However, what truly stood out was the documentation of this prediction pool and the fact that a photo capturing the event still exists.