Both missions--the first originally scheduled for September and the second for October--have been temporarily sidelined while engineers inspect all four shuttles for possible wiring problems.

Managers ordered the inspections after a bent wire was found to be the cause of an electrical short that took out two key main engine computers during the last shuttle launch.

A second flawed wire was later found in shuttle Columbias cargo bay, prompting concerns that the other spaceships could have sustained similar damage during past routine maintenance.

The inspections forced NASA to delay shuttle Endeavours planned launch next month on a scientific mission to map the Earth with radars. The radars were removed from the shuttles cargo bay last week, allowing workers to begin inspections over the weekend.

Shuttle Discovery, which was slated for a mid-October launch to service the Hubble Space Telescope, also is still undergoing inspections.

Kennedy Space Center spokesman Joel Wells said the technicians have uncovered about four potential problem areas in Discovery, but nothing compared to the degree of damage found on Columbia.

Before NASA managers decide which shuttle mission to fly next, they need to know exactly how much work it will take to complete the inspections and any corrections or reinforcements. Each shuttle has about 300 miles of wiring housed in cable trays that line both sides of the orbiters 60-foot-long cargo holds.

Shuttle Endeavour will not be ready to fly its radar-mapping mission until at least Oct. 7. Shuttle Discovery also is targeted for an October flight to the Hubble telescope.

The wiring inspections are not expected to effect schedules for shuttle Atlantis, which is being prepared for a December mission to the International Space Station, or shuttle Columbia, which ferried an X-ray observatory into orbit last month and will soon be taken out of service for a year for refurbishment and upgrades at the shuttles manufacturing plant in California.