A SpaceX Dragon supply ship aborted its initial rendezvous with the International Space Station (ISS) on Wednesday.
Spaceflight Now reports that the cargo vessel, carrying about 5,500 pounds of supplies, experienced difficulties processing GPS navigation data and had to postpone its docking procedure.
The Dragon ship was about 1,200 feet from the ISS when its safety system caused the craft to abort its docking attempt. SpaceX’s mission director reported the bailout to NASA at 3:25 a.m. EST. The craft will attempt another approach as early as Thursday.
“The SpaceX engineers are tracing this issue to an incorrect value that was detected in the spacecraft’s Relative Global Positioning System hardware, which basically tells Dragon’s computers, for its burn plan, where it is in the sky relative to the International Space Station,” Rob Navias of NASA said. “Dragon itself is in excellent shape. Its Global Positioning System hardware is also in excellent shape.”
The approach and docking positioning procedure is designed to be entirely automated, with a few manual commands available as needed. The Dragon uses GPS data to approach the space station, then uses a laser ranging instrument and thermal camera on its close approach.
“SpaceX mission officials are fully confident that that issue can be mitigated, and that the spacecraft can be protected from an incorrect value during the re-rendezvous attempt on Thursday morning,” Navias said. “That will allow Dragon to safely approach the station for a grapple and a berthing to the Earth-facing port on the Harmony module.”
If the Thursday docking attempt is successful, the capsule should be attached to the ISS around 6:00 a.m. EST.
“Dragon has plenty of propellant,” Navias said. “Its other systems are in excellent shape, and all of the science on-board the Dragon can withstand a 24-hour re-rendezvous.”
Experiments arriving on the Dragon ship include equipment for monitoring Earth’s ozone layer, a lightning imager and a testbed that will collect data for satellite servicing missions.