A panel of experts evaluating the space shuttle's readiness to return to flight said yesterday that NASA is still analyzing potential ice damage to the orbiter's heat shielding and said that the agency intends to fly even though in-flight techniques for repairing damage may not be adequate.

Nevertheless, the panel said it found no "show stoppers" to impede a planned July launch and approved several safety measures undertaken after the Columbia disaster, including plans to use the international space station as a "safe haven" for the shuttle crew if the orbiter is too badly damaged to return to Earth.

"We haven't flown yet, and there's ongoing work that still has to be done," said former astronaut and retired Air Force Col. Richard O. Covey, co-chairman of the NASA-appointed Return to Flight Task Group. But "there is nothing out there that we have big questions about that are not the same questions the program itself is looking at."

Chief among these are the effects of chunks of ice breaking off the shuttle's external fuel tank and slamming into the heat shielding during launch. Concerns about ice forming around fittings on the tank, which holds liquid hydrogen and oxygen at temperatures far below zero, caused NASA Administrator Michael D. Griffin in April to postpone the flight of the shuttle Discovery from May to a new launch window that opens July 13.

"The issue is taken very seriously," said Joseph W. Cuzzupoli, head of the task group's technical panel. "I would say only that they're taking the steps they need to take. It's a source [of debris] that could cause a major problem."

For nearly two years, the task group, headed by Covey and retired Air Force Lt. Gen. Thomas P. Stafford, a former astronaut, has been monitoring NASA's compliance with 15 safety recommendations made by the independent Columbia Accident Investigation Board. Leaders of the group briefed reporters on their latest meeting in a telephone news conference from Houston's Johnson Space Center.

Stafford said the group had endorsed NASA's efforts on all but three recommendations, as well as an additional one that NASA imposed on itself: the ability to use the space station as an emergency refuge for seven astronauts from a damaged shuttle until another shuttle could rescue them. Retired Army Col. James C. Adamson, a former astronaut, said NASA had fulfilled the recommendation "in an extremely competent and professional fashion."

The unresolved recommendations involve the issues of ice debris, "hardening" the orbiter and in-flight repairs. The panelists said they expect to complete work on all three by June 27, after completing debris testing and evaluating new windows, new seals and other measures designed to make the shuttle less vulnerable.

But Adamson, the panel's operations chief, acknowledged that the task group was deeply divided on whether NASA's onboard repair techniques for the heat shielding met the intent of the accident board. Several methods will be tested on Discovery, but NASA has acknowledged that all are "works in progress."

"We will either say NASA has met or has not met the intent" of the accident board, Adamson said. "It won't stop us from flying."

Richard O. Covey, co-chairman of the NASA-appointed Return to Flight Task Group, listens to comments by panel member Kathryn Clark during a meeting in Webster, Tex.