About a year ago the National Aeronautics and Space Administration announced the formal termination of the extended mission of Pioneer 10 as of 31 March 1997. On 3 March 1997, the 25th anniversary of the launching of Pioneer 10 was celebrated in Washington, DC at NASA Headquarters and at the National Air and Space Museum. I was among those who gave eulogies for the truly pioneering achievements of this Ames Research Center spacecraft to Jupiter and the outer heliosphere.

The services of the outside contractor for Pioneer 10 operations at the Ames Research Center were, in fact, terminated on 31 March 1997. But, by virtue of informal support by the Deep Space Network and the Ames Research Center, Pioneer 10 has continued to yield valuable data on cosmic-ray intensity in the outer heliosphere throughout 1997 and is expected to do so through at least early summer of 1998. The r.f. telemetry link margin, at 16 bits per second, is still satisfactory and the on-board electrical power from the four radioisotope thermoelectric generators (RTGs) is adequate to operate all essential spacecraft systems plus the University of Iowa's cosmic-ray instrument. A precession maneuver to adjust the pointing of the axis of the spacecraft's parabolic antenna was successfully executed on 3 February 1998.

A special scientific objective during 1998 is to learn whether the cosmic-ray intensity starts to diminish from its 1997 maximum as solar activity increases or whether it increases further to signal approach to the modulation boundary of the heliosphere in the antapex direction.

Until 17 February 1998, the heliocentric radial distance of Pioneer 10 has been greater than that of any other manmade object. But late on that date Voyager 1's heliocentric radial distance, in the approximate apex direction, equaled that of Pioneer 10 at 69.419 AU. Thereafter, Voyager 1's distance will exceed that of Pioneer 10 at the approximate rate of 1.016 AU per year.