CAPE CANAVERAL, SEPT. 1 -- The national space agency today delayed Columbia's astronomy mission until late next week to replace an electronic part used for a telescope inside the shuttle, grounded first by fuel leaks and now cargo problems.

Columbia had been scheduled to lift off today with seven astronauts and the $150 million Astro observatory. The flight was called off Thursday night when NASA discovered the fault.

More than 150 million miles in space, however, NASA's Magellan spacecraft, which had been intermittently incommunicado with its handlers on Earth last month, responded to commands today and signaled it was all right, leading NASA officials to predict that it could resume mapping Venus by mid-month.

Workers at Cape Canaveral entered the shuttle's cargo bay Friday to examine an electronic box at the base of Astro's X-ray telescope. Engineers later concluded a quick fix would not be sufficient, saying a component in the unit or the entire unit will have to be replaced. That ruled out a launch attempt any earlier than Thursday or Friday.

The National Aeronautics and Space Administration had hoped to launch Columbia on Wednesday if the component could be fixed easily.

"Any time we get close and don't go, like a kid going to the carnival, we're frustrated and we're anxious to get going," said William Lenoir, head of NASA's space flight program. "But we're not going until we're ready. I think we're getting awfully close to ready."

The last shuttle flight was in April, when Discovery carried the flawed Hubble Space Telescope into orbit.

The latest delay is not expected to affect Astro's observation schedule, said Lennard Fisk, NASA's chief scientist.

Columbia has until Sept. 14 to lift off, otherwise it will be forced to wait until Discovery carries the sun-probing Ulysses satellite into orbit, Lenoir said.

NASA must launch Discovery between Oct. 5 and 23 to take advantage of the alignment of Earth, the sun and Jupiter, whose gravitational field will fling Ulysses back to the sun.

At NASA's Jet Propulsion Laboratory in Pasadena, Calif., commands radioed 152 million miles across the solar system made the errant Magellan spacecraft easier to control as it orbits Venus.

Engineers have not determined why the spacecraft has suffered two long communications blackouts but said they hoped its $744 million mission to map the planet with radar would begin this month.

Controllers began sending commands to Magellan early today to awaken it from a so-called deep-safe mode and put it in a state called random access memory control.

Nearly six hours after beginning the series of orders, the lab received Magellan's confirmation of the new configuration.

Magellan appeared to be stable, its solar panels were properly pointed at the sun and its batteries charged, the lab said in a statement.

If other maneuvers to normalize the spacecraft's condition go without a hitch, Magellan would be ordered on Sept. 12 to send home radar data already stored on its tape recorder, and its radar sensor would resume operation two days later.