OA-5 Cygnus completes journey to the ISS
Orbital ATK’s latest Cygnus resupply ship completed rendezvous and capture operations with the International Space Station (ISS) on Sunday morning. The OA-5 Cygnus – packed with equipment and supplies for the crew of the orbital outpost – had to wait her turn to arrive, allowing for the docking of the Soyuz MS-02 spacecraft on Friday.
Cygnus OA-5 Arrival:
The latest Cygnus arrival is a significant milestone for the resupply needs of the ISS, having launched on the first upgraded Antares rocket.
The requirement to upgrade the Antares with new engines was due to the loss of the CRS-3 mission, which failed just seconds after lift-off from the Wallops launch site two years ago.
Two interim missions – OA-4 and OA-6 – were successfully launched on United Launch Alliance (ULA) Atlas V rockets, flying out of Cape Canaveral Air Force Station SLC-41 in Florida in December 2015 and March 2016, respectively.
For those missions, the extended Cygnus spacecraft was pushed uphill by the Centaur upper stage. This was also the debut of the larger capacity cargo craft.
During the March mission, the Centaur came to the aid of Cygnus’ orbital requirements, following a shortfall in the Atlas V booster’s performance.
With Antares making her comeback from the CRS-3 failure, the OA-5 mission marked the first time this larger Cygnus will enjoy a push from Orbital ATK’s beefy upper stage.
Both the new Antares 230 configuration and the Castor 30XL upper stage performed without issue, allowing Cygnus to begin her pursuit of the ISS.
However, due to the timing of the mission, Cygnus had to “loiter” on orbit, waiting for the docking of Soyuz MS-02 – containing the precious cargo of three new station occupants – which was completed on Friday.
While patiently waiting her turn, Orbital ATK mission controllers in Dulles, Virginia, spent the early days of Cygnus’ mission uploading and executing the first of a series of rendezvous phasing burns (called DV – Delta Velocity burns) to refine the spacecraft’s trajectory toward the Station.
The first DV burn was conducted in the early phasing period. Lasting approximately 10 minutes, this was designed to raise Cygnus from its initial near-circular 230km orbit to the 400km orbit of the ISS.
A similarly long DV burn followed, again to raise Cygnus to its proper orbital altitude.
This was then followed by a planned phasing burn to align Cygnus into the exact orbital corridor of the Station. A final set of DV burns – conducted over the weekend – brought Cygnus to its “Go/No-Go for Joint-Ops” decision point, which it reached roughly five hours prior to capture.
Once Cygnus received the “go” from MCC-H (Mission Control Center – Houston) for Joint Ops, Cygnus slowly approached the Station to the Joint Targeting Reference Point (JTRP), which it arrived at just over three hours prior to capture.
From this point until capture and berthing, every step of the rendezvous required a strong communications link through the JEM (Japanese Experiment Module) PROX system between Cygnus, the ISS, and ground controllers.
This communication structure ensured the ability to manually abort – or at least retreat – Cygnus’ approach to the Station in the event of a problem with the spacecraft or the ISS.
Once at the JTRP, Cygnus stopped relative motion with the ISS and awaited a second Go/No-Go decision from MCC-H.
At this point, Cygnus was in the Joint Operations Phase (JOPS) of approach, as overviewed in documentation acquired by L2.
Approximately three hours before capture, and with MCC-H providing a “go” to proceed, Cygnus performed the first of four ADV thruster burns (ADV1) to begin moving closer to Station.
During these proximity ADV burns, Cygnus – until capture – made use of the TriDAR vision system designed by Canadian company Neptec with the support of NASA and the Canadian Space Agency.
TriDAR – tested during several Space Shuttle missions – provides Cygnus controllers with real-time visual guidance for navigation, rendezvous and docking procedures.
After Cygnus’ completed her first two ADV burns, the ISS maneuvered to capture attitude – a 5 minute process that took place just over two hours prior to targeted capture time.
Then, MCC-H issued another Go/No-Go decision regarding two more ADV burns for Cygnus, which took the spacecraft to its 250m hold point below the ISS.
MCC-H then gave the “go” for Cygnus to depart the 250m hold point and enter the Keep Out Sphere (KOS) of the ISS.
Cygnus pulsed its thrusters and enter the KOS.
Up until this point, Orbital ATK controllers at their facility in Dulles had full control over Cygnus.
Once Cygnus entered the KOS, NASA controllers at MCC-H joined the Orbital ATK team for the tricky rendezvous and berthing of Cygnus.
Just under half an hour prior to capture, Cygnus arrived at the 30m Hold Point.
Five minutes later, Cygnus received the “go” to proceed to the capture point, at which time it departed the 30m Hold Point just over 15 minutes prior to capture.
Cygnus then arrived at its capture point 12m from the ISS 8 minutes prior to the first capture attempt Expedition 49 astronauts Kate Rubins of NASA and Takuya Onishi of the Japan Aerospace Exploration Agency using the space station’s robotic arm to grapple Cygnus.
Using the Station’s 17.5m Space Station Remote Manipulator System (SSRMS) robotic arm to grab hold of Cygnus, the capture was completed at approximately 07:28 EDT.
After Cygnus was firmly in the SSRMS’s grip, robotic operations maneuvered the craft to Node-1 Unity (delivered by Space Shuttle Endeavour during the first ISS construction mission in December 1998) where the craft was berthed at the ISS.
Next week, the crew will start to unpack than 5,100 pounds of science and research in support of dozens of research investigations, as well as crew supplies and hardware.
This mission involves the seventh Cygnus spacecraft, designated CRS Orbital ATK 5 (OA-5).
Orbital name their Cygnus spacecraft after astronauts, with OA-5 being named the SS Alan Poindexter.
Born in November 1961, Poindexter served in the US Navy including as an F-14 pilot in the First Gulf War and later as a test pilot, before joining NASA in 1998.
He flew aboard two Space Shuttle missions; the first as pilot of Atlantis during the STS-122 mission that delivered the Columbus module to the International Space Station in February 2008.
Cygnus will remain at the space station until November 18, when the spacecraft will be used to dispose of several tons of trash during its fiery reentry into Earth’s atmosphere, and conduct the spacecraft fire experiment.
(Images: Orbital ATK, NASA and L2 including renders from L2 artist Nathan Koga – The full gallery of Nathan’s (SpaceX Dragon to ITS, SLS, Commercial Crew and more) L2 images can be *found here*)
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