Many of the projects won't yield payoffs until after 2000: For example, the Mars unmanned aircraft would be scheduled to pass over Valles Marineris, a huge canyon on the Red Planet, in 2003 -- on the 100th anniversary of the Wright Brothers' first powered flight. The first high-bandwidth links between Martian probes and Earth probably wouldn't be put in place before that time. Even the centrepiece of NASA's spending plan, the International Space Station, won't be completed until 2004 at the earliest. At $13.6 bn (£8.3 bn), NASA's budget for fiscal year 2000 accounts for 0.8 percent of the overall $1.7 trillion (£1 trillion) federal budget proposal. The NASA request is about $87 million (£53 million) less than the current year's funding, following a downward trend that began in 1994 and has almost become a point of pride for NASA Administrator Daniel Goldin. "For the sixth year in a row, NASA's budget has declined while productivity improves," he told reporters Monday. Goldin hoped the projects initiated in 2000 would have a big impact on the world's imagination years from now. "Because NASA doesn't think small... because we plan for the long term, not the short term... this budget is not designed for the next decade. It is designed for the next millennium," he said. Several NASA officials have raised the idea of setting up high-bandwidth links to Mars, the moon and other outposts in the solar system that could feed continuous video and other data back to Earth. We're going to build a network, a solar system Internet if you will," Goldin said. "A series of communication spacecraft that will relay information from planetary bodies back to Earth." Money to begin work on a Mars Network would be drawn from the $250.7 million set aside in the 2000 budget for Mars exploration, according to budget documents. "Mars Network will develop communications capability to provide a substantial increase in bandwidth and connectivity from Mars to Earth," NASA said in a white paper on space science. NASA said it would also work on the development of self-sustaining robotic networks, building on the success of the Mars Pathfinder probe. The goal would be to create "self-tasking, self-repairing, evolvable networks of small, highly mobile rovers for 'virtual presence' planetary science and exploration in challenging environments," the agency said. The International Space Station ranks as NASA's most controversial project, primarily due to Russia's inability to stick to the construction schedule. Most recently, NASA officials have said the launch of the Russian-built Service Module, which is to serve as the first living quarters for space station crews, would be delayed from July to September, 1999. Some NASA documents appear to indicate that the delay could stretch into the year 2000. In the past, such setbacks have led to billions of dollars in projected cost over-runs and a chorus of criticism from congressional skeptics. Next year's $2.48 billion budget request for the space station includes $200 million as an insurance policy in case Russian setbacks cause new cost overruns, plus $148 million for the development of crew return vehicles that could take the place of Russia's Soyuz capsules. Last year, NASA drew up a plan that would provide the Russians with an added $150 million annually for four years, but Goldin said Monday that the Clinton administration has backed away from assigning a specific amount to the Russian space effort. "We believe it would be inappropriate at this time to specify or put that money in the budget," he said, "because it disincentivizes the Russian government to fund the Russian Space Agency," he said. Rep. James Sensenbrenner, the Wisconsin Republican who chairs the House Science Committee, issued a news release Monday criticizing Russia's role in the space station project. But Sensenbrenner's office said the congressman was not yet ready to comment specifically on NASA's 2000 budget request. The idea of sending a robot-controlled airplane over the Red Planet was first raised several months ago, by partners including NASA's Ames Research Center. However, Goldin provided the first indication that NASA would put money into to the project. "I don't know if your heart pumped as much as mine, but this is going to be an incredible achievement," he told reporters. The plan calls for the flight to reconnoiter Valles Marineris at an altitude of several thousand feet on Dec. 17, 2003, exactly a century after the Wright Brothers flight. Cameras mounted on the craft would scan the canyon, getting an unprecedented look at Martian geology and scouting possible landing sites for future probes. Goldin said the aerodynamic challenge of flying such a plane in Mars' thin atmosphere would be equivalent to flying a plane 100,000 to 130,000 feet above Earth -- something that hasn't yet been done but is a goal in NASA's drive to develop "gossamer spacecraft." The NASA chief said funding for the project would be awarded through a competitive process, to be drawn up in the next three to six months. "We have on the order of $50 million (in fiscal year 2000) to do this mission," he said. Although the airplane mission clearly had romantic appeal for Goldin, not all scientists were smitten. "It's public relations first -- and science, if anything, second. Apparently the science, if there is any to be decided on, comes later," said Robert Park, a University of Maryland physics professor and spokesman for the American Physical Society. Goldin said there would be "significantly lower" funding levels for aeronautics and space transportation technology, partly because of a scheduled fall-off in development funding for an experimental reusable launch vehicle known as the X-33. A larger reduction was achieved by discontinuing research programs into supersonic transport and advanced subsonic technology, he said. Instead, NASA would focus on other aerospace technologies, aimed at developing ultra-efficient engines, "synthetic vision" technologies that would allow airline pilots to "see" in any weather conditions, and revolutionary propulsion techniques that would blur the line between air-breathing planes and rockets.