LOS ANGELES (AP) -- NASA officials ordered a 48-hour delay in thelaunch of an atmospheric studies satellite after engineers discovered that ashield was not aligned properly.

The Aura satellite was to have been launched from Vandenberg AirForce Base at 3:01 a.m. PDT (1001 GMT) Sunday aboard a two-stage Boeing DeltaII rocket.

Liftoff was rescheduled for Tuesday, said NASA launch directorChuck Dovale.

An inspector spotted an apparent problem with the satellite'sfairing during a standard walkdown Friday, Dovale said Saturday.

The fairing is a shield that surrounds the satellite duringliftoff. Four seconds after ignition of the second stage, detonators aresupposed to separate the fairing to let it fall away.

The misalignment would have prevented mating the connectors to thedetonation blocks, work that is done close to launch for safety reasons, Dovalesaid. The fairing alignment work is done by Boeing engineers, he said.

Aura, which cost $785 million to develop, carries instruments tostudy the composition of Earth's atmosphere.

The mission's goal is to answer questions about whether thedepleted stratospheric ozone layer is recovering, what processes control airquality, and how climate is changing.

Sunday's launch date was itself the result of a 24-hour delay.

Earlier in the week NASA engineers began reviewing whether``suspect transistors'' affecting an unrelated, non-NASA mission were aboardthe Aura satellite and the Delta II booster and whether they could affect themission.

Engineers determined the transistors were not a problem.