Orbital’s CRS-2/ORB-2 spacecraft has completed her successful mission to the International Space Station (ISS), following unberthing on Friday. The vehicle then spent two days on orbit prior to conducting a destructive re-entry on Sunday – marking the end to Cygnus’ latest Commercial Resupply Services (CRS) mission.
Cygnus ORB-2 EOM (End Of Mission):
Cygnus began her mission last month, launched atop of the Antares rocket from the Wallops spaceport in Virginia.
The spacecraft was carrying a total of 1,664 kg (3,669 pounds) of supplies, including research investigations, crew provisions, hardware, and science experiments from across the country.
“I am very proud of our Antares and Cygnus teams for their exceptional performance on the mission to deliver vital equipment and supplies to the crew aboard the Station,” noted Mr. David W. Thompson, Orbital’s President and Chief Executive Officer.
“I also want to pay tribute to our former Orbital colleague and NASA astronaut, the late Dr. Janice Voss, for whom this spacecraft is dedicated.”
Once berthed to the ISS, the Station crew removed the array of supplies via their “Cargo ops” – that involved the removal of cargo from the “top layers” on port and starboard pallets to make room in pressurized module.
They then removed components from the Secondary Structure, ahead of emptying the forward and aft pallets to gain access to the Standoff pallets, which they then emptied and repacked.
The repack was a near reverse of the cargo ops sequence, filling the Cygnus with cargo to be disposed when the spacecraft is destroyed via re-entry. As such, this cargo won’t be classed as downmass, because – unlike Dragon – Cygnus won’t be returning to the ground or water.
For Cygnus’ departure, ISS management cleared the vehicle for unberthing. The first task was to complete vestibule depressurization, prior to releasing the 16 bolts that had secured Cygnus to the ISS.
The 16 bolts were driven in two stages, while the SSRMS held a firm grip on the spacecraft.
Once released, Cygnus was carefully translated 10 meters away from the Station, eased through pre-planned manuevers to position the vehicle into her release stance.
The Latching End Effector on the end of the Station’s arm then drove the snares to literally let go of Cygnus, allowing her to be free once again, followed by the ISS crew slowly moving the arm back away from the ship from their viewing position in the Cupola’s Robotic Work Station (RWS).
The unberthing operations were conducted by NASA Flight Engineer Reid Wiseman and Expedition 40 Flight Engineer Alexander Gerst of the European Space Agency.
With Cygnus able to abort, should she wander back towards the arm – as was the case with the HTV-3 unberthing – controllers both at MCC-Dules and MCC-Houston conducted system checks, prior to the opening departure burn.
This initial departure was a commanded abort, a nominal procedure to allow the HTV console to inform Cygnus she can begin to move away.
Cygnus then headed out of the Keep Out Sphere (KOS), before eventually departing the Approach Ellipsoid, marking the point where joint operations between NASA and Orbital ended. Orbital’s controllers in Dulles then took control of the spacecraft.
To complete her mission, known as EOM (End Of Mission) she conducted two standard burns and the final deorbit burn – towards a destructive re-entry, with break up occurring high above the Pacific Ocean at 75 km altitude.The event occurred on Sunday, allowing Station crew members an opportunity to photograph Cygnus’ fiery reentry back to Earth in order to gather engineering data that could be applied to the entry path of the European Space Agency’s Automated Transfer Vehicle cargo ship in January, 2015.
The final phase of the Cygnus mission was called the Descent & Reentry Operations Phase (DROPS), as Cygnus ended her life in a disposal corridor during entry, marking the conclusion of the latest in a series of CRS mission for the Cygnus fleet.
The deal to carry out ISS resupply flights – under the $1.9 billion CRS contract – encompasses eight missions between 2012 and 2015 carrying approximately 20,000 kg of cargo to the ISS.
Additional missions will be ordered via the CRS2 contract awards in the near future, based on the recent US decision to back an extension of the ISS’ lifetime to 2024.
(Images: via L2′s Cygnus Section – Containing presentations, videos, a vast set of unreleased hi-res images, interactive high level updates and more, with additional images via Orbital and NASA).
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