With the Earth in the background, the International Space Station is featured in this image photographed by an STS-130 crew member from aboard the Space Shuttle Endeavour in this photo released by NASA and taken February 9, 2010. REUTERS/NASA Handout

The space shuttle Endeavour is silhouetted against the backdrop of Earth's horizon prior to docking with the International Space Station in this picture taken by an Expedition 22 crew member on February 9, 2010 and released by NASA February 12, 2010.

A setting last quarter crescent moon and the thin line of Earth's atmosphere are photographed by an Expedition 24 crew member as the International Space Station passes over central Asia September 4, 2010 in this NASA handout photo obtained September 10, 2010. Picture taken September 4, 2010. REUTERS/NASA/Handout

The space shuttle Discovery is seen with Earth in the background as the shuttle approaches the International Space Station for docking in this February 26, 2011 photograph by an Expedition 26 crew member released by NASA. Shuttle Discovery astronauts worked alongside the International Space Station crew on Sunday to prepare the orbital outpost for life after the United States retires its three existing spaceships. Picture taken February 26, 2011. REUTERS/NASA

This unprecedented view of the space shuttle Atlantis, appearing like a bean sprout against clouds and city lights shows the shuttle on its way home as photographed by the Expedition 28 crew of the International Space Station through a window of the station in this July 21, 2011 NASA handout photo. Airglow over Earth can be seen in the background. The Atlantis and its four-member crew returned to the Kennedy Space Center in Florida on Thursday after a mission to resupply the International Space Station, ending a 12-year program to build and service the orbital research outpost. REUTERS/NASA/Handout (SCI TECH IMAGES OF THE DAY) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS

A full moon is visible with part of the International Space Station's solar array wing in this view above Earth's horizon, photographed by a crew member from the International Space Station while Space Shuttle Discovery (STS-128) remains docked with the station in this NASA handout photo taken September 3, 2009. REUTERS/NASA/Handout (UNITED STATES SCI TECH IMAGES OF THE DAY) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS

A night time photograph made by an International Space Station Expedition 25 crewmember shows the bright lights of Cairo and Alexandria, Egypt on the Mediterranean coast as well as the Nile River and its delta which stand out clearly in this image released by NASA and taken October 28, 2010. REUTERS/NASA (UNITED STATES - Tags: SCI TECH) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS

The International Space Station is visible with the Earth in the background in this photo released by NASA and taken November 25, 2009. Picture taken November 25. REUTERS/NASA/Handout (UNITED STATES SCI TECH IMAGES OF THE DAY) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS