As it stands now, Atlantis and its crew are scheduled to return to Earth Feb. 18. The planned March 1 launch of sister ship Discovery, as a result, is being delayed until March 8 to give engineers ample time to review critical systems performance data from the Atlantis flight.

"The March 8 launch date will accommodate the time needed between the Atlantis landing and the Discovery launch to complete the flight data review from the Atlantis mission," Kennedy Space Center (KSC) spokesman Joel Wells said Thursday.

NASA typically allots a week or two between a landing and launch of its next shuttle flight so that engineers can perform preliminary inspections of recovered solid-fuel rocket boosters and pore over performance data from other critical systems.

The idea is to allow enough time to flag any dangerous technical problems that might jeopardize the crew of a follow-on shuttle flight.

A good case in point: Post-flight inspections of the solid-fueled rockets used to propel shuttle Endeavour into space Nov. 30 showed that small explosive device associated with the ships booster-separation system failed to fire.

A backup worked as expected, and the shuttles left-hand booster separated cleanly. But the failure -- which was traced to a damaged cable -- prompted the extra inspections that delayed the upcoming Atlantis flight.

Similarly, inspections after shuttle Discoverys most recent flight in October showed that 10 of its steering thrusters would have to be replaced. That work prompted an initial delay from Feb. 15 to March 1 in that shuttles next mission to ferry a fresh crew up to the international station.

With the Discovery launch now off until March 8, the stations current crew -- U.S. astronaut Bill Shepherd and Russian cosmonauts Yuri Gidzenko and Sergei Krikalev -- wont return to Earth until about March 20 -- or almost a month later than originally planned.

Shepherd and company, however, say a tardy return is no big deal.

"I think you have to approach it from the standpoint of you get home when you get home," Shepherd said earlier this week.

"Yuri and I are military folks and weve been in this kind of arrangement for some time. Sergei has a lot of experience flying in space [and] hes probably the expert on flight delays, having done two increments back to back on the Mir [space station]," he said.

"So I think its something we have been conditioned to. We dont expect big delays, but certainly were mentally prepared to deal with it."

Like waves on a pond, meanwhile, the Atlantis delay will have a ripple effect on other shuttle missions scheduled for launch this year.

A planned April 19 launch of shuttle Endeavour on a mission to deliver a Canadian-built robot arm to the station remains on track. But the scheduled May 17 launch of shuttle Atlantis with a station airlock is being bumped to no earlier than June 8, Wells said.

Consequently, the planned June 21 launch of Discovery on a follow-on station assembly mission will be pushed back to a still-to-be-determined date in July -- probably around July 12.

The rest of NASAs shuttle schedule for the year, meanwhile, is "under review," Wells said.

Endeavour still remains scheduled for an Oct. 4 mission to the station, but only one of two planned missions aboard Columbia is expected to get off the ground this year.

NASA had hoped to launch Columbia -- which now is undergoing extensive inspections and repairs at a shuttle assembly plant in California -- on a science mission in August and then a Hubble Space Telescope servicing flight in early December.

Some seven to eight months of work, meanwhile, will be needed to prepare Columbia for its next launch once it returns to KSC in late February -- or about five months later than planned.

Consequently, NASA officials say either the science mission or the Hubble servicing flight likely will be delayed until sometime in early 2002.