Iceland Volcano's Ash Cloud No Threat to Space Shuttle Landing

Thisstory was updated at 4:51 p.m. ET.

Theash cloud belched by an erupting volcano in Iceland may have disrupted airtraffic over much of Europe, but it poses no threat to NASA's planned Mondaylanding of space shuttle Discovery, agency officials said.

WhenDiscovery re-enters the Earth's atmosphere Monday morning, it will be flyingover the northern Pacific Ocean on a course that will take it over much ofNorth America before it is due to land at NASA's Kennedy Space Center inFlorida at 8:58 a.m. EDT (1258 GMT).

Thattrajectory is well clear of the ash cloud from Iceland'sEyjafjallaj?kull volcano, which has caused the worst global air trafficdisruption ever seen, except during major wars, according to press reports.

"Thatsmoke cloud will not cause Discovery any sort of issues during its re-entry onMonday," NASA spokesperson Josh Byerly said Saturday during missioncommentary.

Discoverywill re-enter the Earth's atmosphere far to the east of the regions of Europeand Asia where the effects of the volcanic ash cloud have been the most severe,Byerly said. The space shuttle will begin re-entering the atmosphere at a pointover the northern Pacific Ocean about 650 miles (1,046 km) south of the AleutianIslands near Alaska, he added.

Discoveryundocked from the International Space Station early Saturday and iswrapping up a 14-day mission that delivered nearly 8 tons of cargo to theorbiting laboratory. The shuttle is returning about 3 tons of trash andunneeded items back to Earth. [Photosfrom Discovery's April 5 launch.]

Byerlysaid Discovery's seven-astronaut crew and the six astronauts living aboard theInternational Space Station have not been able to actually see Iceland'sEyjafjallaj?kull volcano due to inclination of their orbit. Iceland is at alatitude too far north on Earth for the astronauts on Discovery and station tosee it from their respective orbits, he added.

Thespace station typically flies in an orbit tilted about 51.6 degrees withrespect to Earth's equator and at an altitude of about 220 miles (354 km).

"Thereis a chance that the crew on the station may have been able to get some imagesof the haze that is over parts of Europe," Byerly said. "But so far,the shuttle and the station crews haven't' been able to see any of the remnantsof that volcano, much less the volcano itself because their orbit doesn't takethem high enough to cross over that part of the world."

SeveralNASA satellites, however, have been monitoring the volcano's eruption and ashcloud closely to measure their intensity and effects on the environment.

Inaddition to creating widespread air traffic woes on Earth, the Eyjafjallaj?kullvolcano's ash cloud has led to somespectacular sunsets in parts of the world.

Scientistshave said the eruption is still too small to have a significantimpact on Earth's climate, but could have a larger effect if the eruptionsin Iceland continue or get bigger.

Meanwhile,Discovery and its crew are preparing for a Monday landing to wrap up what hasbeen a busy space mission complicated by antenna malfunctions and sticky boltsand valves of all sizes.                                          

Whenthe astronauts re-enter the atmosphere Monday morning, they will be flying whathas become a rare flight profile over much of North America and the UnitedStates in what NASA flight controllers call a "descending node"profile. NASA has tended to avoid flying over land as much as possible sincethe 2003 Columbia accident, which spread debris over much of Texas andsurrounding regions when that shuttle broke apart during re-entry due to heatshield damage.

Discovery'sheat shield, however, is in tip-top shape and engineers cleared the shuttleSaturday for its upcoming re-entry and landing.

Byerlysaid early-bird skywatchers in North America will get a treat if they rise inthe morning to try to glimpse Discovery's plasma trail across the sky duringits Monday re-entry.

"Itis a once in a lifetime opportunity," Byerly said.

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SPACE.comis providing complete coverage of Discovery's STS-131 mission to theInternational Space Station with Managing Editor Tariq Malik and Staff WriterClara Moskowitz based in New York. Clickhere for shuttle mission updates and a link to NASA TV.