A Guide to Cygnus’ Orbital Maneuvers

Illustration of Cygnus in orbit. (Credit: Orbital Sciences Corporation)
Illustration of Cygnus in orbit. (Credit: Orbital Sciences Corporation)

Cygnus Mission Update
Via Orbital Sciences Corporation
September 20, 2013

Before Cygnus can rendezvous and berth with the International Space Station (ISS), it must perform several thruster firings to raise its orbit and catch up with the ISS. Cygnus must also perform 10 maneuvers to demonstrate the safety capabilities of the Cygnus. Once each demonstration maneuver is complete, Orbital will send a data package to NASA for review to verify that the demonstration has met its objectives.

Since the launch of the spacecraft at 10:58 a.m. on Wednesday, September 18, the Cygnus team has been busy completing the first two of 10 required in-orbit demonstrations and has successfully conducted three Delta V burns to raise Cygnus’ orbit. On Friday, September 20 , the team will conduct Delta V burn #4 to raise Cygnus’ orbit to within 4 km of the ISS orbit altitude. If needed, an additional burn may be conducted in Saturday, September 21, to “fine tune” Cygnus’ orbit.

The Cygnus team is busiest on Sunday, September 22, the day of rendezvous, grapple and berthing with the ISS. That day, the remaining eight demonstrations and a series of smaller Approach Delta Velocity (ADV) burns will be carried out prior to capture by the station crew and berthing with the ISS.

Once the final demonstration maneuver is deemed successful, NASA will give approval for the approach to within 10 meters of the station where Cygnus will be grappled by the robotic arm and guided to its berthing port.

DATE/
STATUS
MANEUVERGOAL
CompletedFree drift & abort demonstrationDemonstrate the spacecraft’s ability to float freely with all of its thrusters inhibited and to safely move away from the station if necessary
9/22Position and attitude control demonstrationTest the spacecraft’s ability to hold its position
9/22Relative GPS navigation demonstrationVerify the spacecraft’s GPS-based navigation system is operating as expected
9/22Onboard targeting demonstrationConfirm the spacecraft’s ability to maneuver to a targeted position in space
ADV 1Raises Cygnus from 4 km below ISS to 1.4 km
9/22Reaction Engine Assembly (REA) maneuver demonstrationDemonstrate Cygnus’ attitude control system’s ability to maneuver
ADV 2Moves Cygnus closer to R-Bar (directly below the ISS)
9/22Hardware Command Panel (HCP) checkoutVerify that the ISS crew can command Cygnus using the HCP aboard the Station
ADV 3Positions Cygnus to intersect the R-Bar
9/22LIDAR navigation demonstrationConfirm that Cygnus’ laser navigation sensor’s position and velocity data is accurate and as expected in prefight simulations
ADV 4Continues Cygnus’ ascent on the R-Bar toward 250m
9/22ADV 5Continues Cygnus ascent up the R-bar
9/22Retreat demonstrationVerify that the ISS crew can command Cygnus to retreat away from the ISS, if needed
9/22Hold demonstrationVerify that the ISS crew can command Cygnus to hold during approach, if needed
9/22LIDAR single reflector tracking demonstrationDemonstrates Cygnus’ LIDAR’s capability to focus on a single reflector on the ISS