As we eagerly anticipated the moment when Voyager 2 would reach the boundary of Neptune’s influence in the solar wind, we decided to keep things interesting by organizing a prediction pool among the science teams at the Jet Propulsion Laboratory. To do so, we used a chalkboard 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, all 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, we needed to add seven hours and then subtract four hours and six minutes to adjust for the event occurring on the spacecraft earlier. This resulted in a two-hour and fifty-four minute difference.

My prediction was set for 12 noon on DOY 236, which was August 24th at 1454 GMT-SCET. To my surprise, 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 not only this remarkable achievement but also the documentation of our prediction pool and the fact that a photo capturing this historic moment still exists.