SpaceX’s CRS-10 Dragon spacecraft successfully arrived at the International Space Station (ISS) this morning, a day late, but with none of the problems that arose in its first attempt yesterday. Meanwhile, Russia’s Progress MS-05 spacecraft is continuing on its journey to the ISS and will dock tomorrow morning. Together, they are bringing 5.4 metric tons (MT) of supplies to the six person crew.

Dragon’s first attempt was aborted yesterday because of a problem with its GPS navigational system. Dragon’s on-board computers recognized an incorrect value in navigational data about the spacecraft’s position relative to the ISS and automatically terminated the arrival sequence, placing itself into a holding pattern on a “racetrack” trajectory around the ISS while ground controllers diagnosed and fixed the problem. Other than the navigational error, the spacecraft was in perfect shape.

Dragon does not dock with the ISS, but is berthed to it. Once it reaches a point 10 meters from the ISS, astronauts use the robotic Canadarm2 to reach out and grab it. Once it is in Canadarm2’s grasp, ground controllers move it over to a docking port and install it onto the port. In this case. Dragon was grappled by Canadarm2 at 5:44 am Eastern Standard Time (EST), a few minutes ahead of schedule. It will be berthed to the Harmony port at about 8:30 am EST today.

Launched on Sunday, also a day later than originally planned, this is SpaceX’s 10th operational cargo mission to the ISS for NASA under the Commercial Resupply Services (CRS) contract and is designated SpaceX CRS-10 or SpX-10. Dragon is full of 2.5 metric tons (5,500 pounds) of supplies, scientific experiments, and equipment. It will remain docked to the ISS for about a month and then return to Earth. Dragon is the only one of the four spacecraft (Russia’s Progress, Japan’s HTV, and the U.S. Dragon and Cygnus) that resupply ISS that is designed to survive reentry. Thus it can return the results of scientific experiments and equipment that needs repair or replacement.



SpaceX CRS-10 (SpX-10) Dragon captured by International Space Station’s robotic Canadarm2, February 23, 2017. Photo credit: NASA

Russia’s latest cargo spacecraft, Progress MS-05, was successfully launched yesterday. It docks with the ISS under its own power and is due to arrive at 3:34 am EST tomorrow. It is carrying 2.9 MT of propellant, oxygen, water, and dry cargo.

ISS is a partnership of the United States, Russia, Canada, Japan and 11 European countries. The crew members currently aboard are NASA’s Peggy Whitson and Shane Kimbrough, Europe’s Thomas Pesquet, and Russia’s Andrey Borisenko, Sergey Ryzhikov, and Oleg Novitsky. Pesquet and Kimbrough were at the Canadarm2 controls this morning for the grapple.