ISS Resupply - Orbital ATK
OA-7 delivered 3800 kg of supplies and science experiments to the ISS
On April 18, 2017 an ATLAS V rocket blasted off from Kennedy Space Center. This rocket was used to launch the Orbital ATK built Cygnus Commercial Resupply Vehicle on the OA-7 mission to the International Space Station (ISS).
Orbital ATK developed the Cygnus advanced maneuvering spacecraft in conjunction with NASA under the agency’s Commercial Orbital Transportation Services (COTS) program. For the OA-7 mission, the Cygnus advanced maneuvering spacecraft carried approximately 3800 kg of supplies and science experiments for the ISS. This work was carried out under the Commercial Resupply Services (CRS) contract that Orbital ATK has with NASA. OA-7 represents the seventh of these resupply missions.
Neptec’s TriDAR provides 3-D eyes for Cygnus
Installed on Cygnus were two of Neptec’s TriDAR rendezvous and docking laser systems. A combination of high-precision, near-field triangulation with a long-range Time-of-Flight (LiDAR) sensor, TriDAR provides automated, real-time visual guidance for navigation, rendezvous and docking procedures.
The Cygnus spacecraft is equipped with Star Trackers and an absolute GPS system to determine its position in orbit during free flight. During rendezvous with the ISS, Cygnus switches to relative GPS to determine its position relative to the station. When beginning proximity operations, Cygnus starts using Neptec’s TriDAR system.
How does TriDAR work?
TriDAR does not rely on any reference markers positioned on it’s target, instead it uses a laser-based 3D sensor and thermal imagers to collect 3D data of its target that is then compared by software to the known shape of the target spacecraft. TriDAR uses this information to calculate relative range, rates and 6 degrees of freedom relative position between the spacecraft and the ISS. This information is used by the vehicles automated systems to allow the Cygnus Service Module to approach the station and position itself for capture by the station’s robotic arm. The TriDAR systems are used during the final rendezvous phases for a maximum range of approximately 1000m (1km) down to the final capture location at ~10m from the ISS. At this capture location the vehicle is grappled by the station’s crew using the station’s robotic arm and then subsequently connected to the station via a node port.
Neptec has provided Orbital ATK with TriDAR units for the completion of the first phase of the CRS program. Currently Neptec is under contract to provide additional TriDAR units for the next program phase (CRS2).
Cygnus Image credit NASA