### Interplanetary

The 80s could be called the decade of near misses. Only two major projects were initiated in the 1980s, and one was ignored. These projects were the Magellan spacecraft, which was to be sent to the Planet Venus, and the Galileo probe that was to be sent to the Planet Jupiter. Both were launched late in the decade with the majority of their data being collected in the 90s. The one missed opportunity was to send a spacecraft to fly-by Haley's Comet.

Venus was last explored by American spacecraft Pioneer-Venus 1 and 2 and had performed low-resolution radar traces of almost the whole planet. The Magellan probe was to perform a high-resolution radar mapping of Venus. The Russians had done this earlier but at a much lower resolution. Because of increasing scientific mission requirements and rising project costs, Magellan was slated to be canceled. But the project was reduced to totally focusing on the radar-mapping mission only. By borrowing an old communications dish from the Voyager program, and using it for both the radar mapping mission and communicating with Earth lowered the costs enough to keep the mission. Launched in 1989 from the space shuttle and using an Inertial Upper Stage (IUS) to send the spacecraft into outer space, Magellan arrived at Venus in 1990 and completed its mission by 1993. It showed Venus to be more volcanically active than previously thought with many deep canyons and valleys like Mars.

The last time an American probe investigated Jupiter was Voyagers 1 and 2 in the 1970s, which were just fly-by missions. The scientific community wanted a more thorough, focused examination of our solar system's largest planet. Galileo was designed and built by the Jet Propulsion Lab (JPL), and was originally planned to be launched from a space shuttle with a high-performance Centaur upper stage to send it on its way to Jupiter in the mid 1980s. But with the CHALLENGER disaster, use of the liquid oxygen / liquid hydrogen Centaur upper stage on the shuttle was ruled to be too dangerous. So Galileo was put back into storage, and JPL planners looked at the Titan rocket as a new launch vehicle. Because the Centaur vehicle was not quite developed yet, the only available upper stage was the two-stage solid-propellant Inertial Upper Stage, and it would also call for using planet gravity assists to get to Jupiter. This had been done before on the Pioneer 10 and 11 series, the Voyager 1 and 2 spacecraft, and the Mariner 10 probes. But the Galileo gravity-assists required multiple assists that had never been attempted before. Galileo was launched in 1989 aboard a space shuttle, and would not reach Jupiter until the mid-90s. It had troubles from the beginning. The major problem was the inability of the high-gain antenna to completely deploy. Therefore ground controllers had to resort to the low-gain antennas. But high hopes were held out for the program.

The major disappointment for the 1980s was the missed opportunity to send a major American probe to investigate Haley's Comet. Haley's Comet comes in the vicinity of Earth only once every 76 years, but scientists were unable to convince Congress of the importance of the project. Eventually ESA, the Soviet Union and Japan sent spacecraft to explore the comet.

Nicholas M. Short, Sr. email: nmshort@ptd.net
Jim Rosalanka (jrosolanka@worldnet.att.net)