A spacewalk originally scheduled for Thursday, October 19, will be postponed until later this year as NASA managers and engineers review a leak of coolant from the backup radiator of the International Space Station's Science Multipurpose Experiment Module.

Four members of Expedition 70 took a group photo in the crew module of the International Space Station's "Harmony". Clockwise from bottom are: NASA astronaut Jasmin Moghbeli, ESA (European Space Agency) astronaut Andreas Mogensen, JAXA (Japan Aerospace Exploration Agency) astronaut Satoshi Furukawa and NASA astronaut Loral O'Hara. Source: NASA

The spacewalk date was adjusted to give engineers more time to complete analysis of coolant leaks. The coolant is not toxic or hazardous to occupants, but experts are discussing how best to prevent trace amounts of the substance from entering some internal systems to avoid equipment degradation over time. The mission of this spacewalk plan is not time-sensitive, and time adjustments will have no impact on the operation of the space station.

The spacewalk planned for Monday, October 30, now becomes U.S. Spacewalk 89. During this spacewalk, NASA astronauts Loral O'Hara and Jasmin Moghbeli will exit the space station's exploration airlock to complete the removal of a failed electronics box (called a radio frequency group) from a communications antenna bracket and replace one of the twelve shaft bearing assemblies of the port side truss Sun Alpha swivel joint. These bearings allow the space station's solar arrays to rotate properly to track the sun as the station orbits the Earth. During this spacewalk, Mogbeli will serve as EVA crew member No. 1, and O'Hara will serve as EVA crew member No. 2. This will be O'Hara and Mogbeli's first spacewalk.

The north coast of Baja California Sur, Mexico, in the Pacific Ocean, taken from the International Space Station, which was orbiting 258 miles above. Image source: NASA

Later this year, O'Hara and ESA astronaut Andreas Mogensen will conduct the United States' 90th spacewalk to collect samples for analysis to determine whether microorganisms are present outside the orbital module. They will also replace high-definition cameras on the station's port truss and perform other maintenance work in preparation for future spacewalks.

Meanwhile, the spacewalk of Roscosmos cosmonauts Oleg Kononenko and Nikolai Chub is still scheduled to take place on Wednesday, October 25. During this spacewalk, Kononenko and Chubu will install a synthetic radar communications system on the Russian portion of the orbiting laboratory and deploy a nanosatellite to test solar sail technology. In addition, they plan to inspect and photograph the leaking spare radiator on the Nauka multi-purpose experimental module.

Southern Italy (right side of the picture) borders Sicily (left side), the largest island in the Mediterranean and one of Italy's 20 regions. Sicily is only 2 miles (about 3.2 kilometers) away from the nearest mainland, and the two are connected through the Strait of Messina. From an altitude of 260 miles, the International Space Station provides a unique perspective on the intersection of these two regions. Source: NASA

Preparations for a spacewalk on the International Space Station continue, with Expedition 70 astronauts and astronauts overhauling their spacesuits on Monday. Cargo operations are also underway, with orbiting residents working inside the Cygnus space cargo vehicle and looking ahead to the next SpaceX Dragon cargo mission.

A photo of the Caspian Sea and coastal towns in northern Iran taken from the International Space Station, which was orbiting 259 miles above. Image source: NASA