WHILE attention has focused on the Astro observatory that Columbia will take into orbit and on the Hubble telescope, another astronomical spacecraft has quietly arrived at the Kennedy Space Center. It's Ulysses, the NASA-European Space Agency (ESA) solar explorer. Its long-delayed mission to study the sun, the solar wind, and interstellar space has become both a symbol and a test of the United States' ability to act effectively as a partner in international space ventures. The Christic Institute, the Florida Coalition for Peace and Justice, and the Foundation on Economic Trends, which tried to stop the launch of the Galileo Jupiter mission, now are trying to halt Ulysses. They raise again the groundless claim that the spacecraft's plutonium-fueled radioisotope electric generator presents an unacceptable environmental risk.
It would be a tragedy if this protest were to succeed. Failure to launch the mission for this or any reason other than equipment failure would enhance the significant doubts Europeans already have about the ability of the United States to fulfill its international space commitments.
As originally conceived, the Ulysses mission involved two spacecrafts to be supplied, respectively, by ESA and NASA.
In a unilateral move, White House budget manipulators nearly a decade ago forced NASA to renege on part of what ESA still regards as a solemn agreement. NASA canceled the American spacecraft. This left what now is the Ulysses craft to carry out this major mission. As things worked out, ESA has built the spacecraft, NASA and ESA have supplied its instruments, and the shuttle Discovery is to launch it during a 19-day window that opens Oct. 5.
ESA eventually forgave the US action. But suspicion of US integrity as a partner remained. It has surfaced again as the space-station Freedom program - in which ESA is a major partner - has undergone repeated unilateral redesigns. Thus the United States has to show that it can finally come through with the Ulysses mission.
The antinuclear protesters claim, as they did with Galileo, that a launch failure might spread the plutonium in the generator into the environment. This is highly unlikely. As the Galileo court hearings brought out, NASA has carefully explored that contingency. The generator is packaged to prevent plutonium escape.
The protesters claim that NASA has not adequately considered using advanced solar cells to power the craft. But as NASA notes, such cells wouldn't be available until 2000. Radioisotope power is essential for deep-space voyages. The plan is to arrive at Jupiter in February 1992 and to make the first solar approach in May 1994. This timing allows Pioneer and Voyager spacecraft, now leaving the solar system, to work with Ulysses to build up a three-dimensional picture of the sun's sphere of influence.
It is important for this mission to get under way. If a united Europe - including Germany, where Ulysses was built - finds the US irrelevant to its space activities, it could become a formidable space competitor rather than a valued partner.