The life of Tom Gehrels

Page, Arizona, is not known as a launch site for high-altitude research balloons, but that is where Tom Gehrels was with his polariscope balloon payload in 1968. The National Scientific Balloon Facilities (NSBF) team was testing balloon launches in Page, trying a new technique of inflating the balloons in the wind-quiet spot in Glenn Canyon just below the new Glenn Canyon dam. The bubble is released and carries the payload straight up until it rises out of the canyon where it catches the wind above … hopefully not blowing hard enough to slam the payload into the side wall on exit! Polariscope was an instrument to measure the polarization of solar system bodies and interstellar dust grains. It was a prototype for an instrument on the Pioneer space-craft to fly-by the major planets in the 1970s. It was an innovative instrument that detected weak polarization with a rotating polarimeter that scanned repeatedly across the object of interest. It flew four times successfully, providing solid engineering proof of concept. Still, the Pioneer proposal was a long shot since Gehrels and his team did not have previous spaceflight experience. In the end, it was successful based on the ingenuity of the design and balloon test. Interestingly, this polarimeter turned out to be the only imaging instrument on Pioneers 10 and 11 and so made popular headlines for producing the first in situ pictures of Jupiter and Saturn. The Gehrels story leading to Tucson and polarimetry is a fascinating one, known to many through his autobiography On the Glassy Sea (Gehrels 1988). Tom (Anton M. J.) was born in 1925, as the youngest of five children, on a large wheat and potato farm in the Haarlemmermeer polder, not far from Amsterdam. When he was a teenager, one of his older brothers inherited the farm and his family moved away from the polder, settling in the city of Baarn, a suburb of Amsterdam.