Voyager 2’s Magnetic Encounter with Neptune: A Look Back at the Excitement and Anticipation at JPL

Excitement was palpable at the Jet Propulsion Laboratory (JPL) as we eagerly awaited Voyager 2’s encounter with Neptune’s magnetosphere. We set up a prediction pool to guess when the spacecraft would encounter the “bow shock” of the planet’s magnetosphere. A chalkboard in one of the rooms at JPL was used to create a list, which was assigned to the science teams.

The prediction was in Pacific Daylight Time-Earth Received Time (PDT-ERT), which is when the data arrived back at JPL in California. Only five entries were made, starting from Day of Year (DOY) 235, which is August 23rd in non-leap years. The one-way light time during the flyby was 4 hours and 6 minutes. Converting the spacecraft event time (SCET) from PDT-ERT to Greenwich Mean Time (GMT) required adding 7 hours, then subtracting 4 hours and 6 minutes to adjust for the spacecraft’s time.

My guess was later than the others, anticipating a smaller magnetic field that would be seen closer to the planet. I predicted 12 noon on DOY 236, which translates to August 24th at 1454 GMT-SCET. The Plasma Science experiment actually detected the bow shock on August 24th at 1438 GMT-SCET, not too far off from my guess.

It is truly remarkable that this event was documented and that a photo of the prediction list still exists, capturing our excitement and anticipation of Voyager 2’s encounter with Neptune’s magnetosphere.