The OA-9 (S.S. J.R. Thompson) Cygnus has arrived at the International Space Station early Thursday morning. During the approach, Cygnus became the first craft to use the new Common Communications for Visiting Vehicles (C2V2) radio – which will be instrumental for the upcoming commercial crew vehicles. During its stay at ISS, Cygnus will hopefully perform a Station orbit raising test – making Cygnus the first American craft to reboost the Station since the retirement of the Space Shuttle fleet seven years ago.
After a flawless launch from the Mid-Atlantic Regional Spaceport in Wallops, Virginia, the OA-9E Cygnus completed the arrival sequence to the International Space Station following four days of orbit-raising and phasing maneuvers to properly bring itself to the vicinity of the ISS.
The exact timing, duration, and delta-Velocity (delta-V) changes to the phasing burns Cygnus performed changed from the pre-launch plan given that the craft launched at the end of its five minute launch window instead of at the beginning. Click this link to compare the detailed burn times and delta-V changes between the anticipated launch and actual launch times on L2.
Nevertheless, the trajectory the S.S. J.R. Thompson followed its Final Approach to the Station the same as previous Cygnus missions, with the craft approaching the ISS from behind and underneath (between the Station and the Earth) before arriving on the R-Bar, radial velocity vector, and drifting upward to its 10 m capture point.
However, one element of this arrival was vastly different from all previous Cygnus missions. Those eight prior Cygnus flights have made use of the JEM (Japanese Experiment Module) PROX system between Cygnus, the ISS, and ground controllers to ensure continuous communications between the three entities.
This use of the JEM PROX system was completely different than the one used by SpaceX’s Dragon cargo capsule. Therefore, in an effort to streamline communications for all visiting vehicles to the USOS (U.S. Operating Segment) of the Station, NASA mandated that all vehicles switch to a new communication system known as the Common Communications for Visiting Vehicles (C2V2) radio.
With this Cygnus flight, this was the first time the new C2V2 radio was used, with Orbital ATK’s Frank DeMauro, Vice President and General Manager of its Advanced Programs Division, in an exclusive interview with NASASpaceflight’s Chris Gebhardt stating, “NASA, for CRS2, put the requirement that we had to switch to C2V2, and so we decided to do that earlier than CRS2 and this is going to be the first mission that we fly that system.
“It has been through enormous amounts of testing. It’s a very important system, not only at the hardware level but at the spacecraft level. We’ve done interface tests with NASA and the TDRS (Tracking and Data Relay Satellite) network, and NASA has done their own testing, making sure that the entire network checks out. So we have very high confidence in the system, and we’re looking forward to demonstrating this comm system on this mission.”
The new C2V2 system operates in much the same way as previous Cygnus communication systems did, with Cygnus transmitting and sharing its data simultaneously with its control center in Dulles, Virginia; Mission Control Houston; and the Station crew working in the Robotics Work Station in the Cupola lab.
From Cupola, the Station crew had the ability to not only monitor all of Cygnus’ health parameters as it approaches the ISS but also to initiate an abort of the rendezvous sequence should Cygnus demonstrate an off nominal condition – as has happened before.
“When we’re in the proximity of ISS, we have to share telemetry [through the C2V2], but it’s also how the crew can command the vehicle if we ever need an abort,” noted Mr. DeMauro. “They could command it directly from the ISS, and that signal would get sent directly to Cygnus and we would fly away. So [the C2V2 is] a very important system.”
The C2V2 will eventually eliminate the use of multiple communication systems from the various Visiting Vehicles arriving to the U.S. segment of the Station, unifying all communications through a single system. This will be especially important when SpaceX’s crew Dragon and Boeing’s CST-100 Starliner crew vehicles perform their uncrewed test flights later this year and begin carrying crew after those initial demonstration flights are complete and validated.
For the S.S. J.R. Thompson, the new C2V2 radio guided the vehicle through its approach and various hold points during the rendezvous sequence, eventually bringing Cygnus to its 10 m capture point, at which time the Station crew reached out with the Space Station Remote Manipulator System (or Station Arm) and grapple Cygnus.
Grapple came at approximately 05:26 EDT (09:26 UTC) Thursday morning followed by berthing to Node-1 Unity’s nadir Common Berthing Mechanism port, expecting two hours later at 07:30 EDT (1130 UTC).
Arrival of the S.S. J.R. Thompson marked the commencement of nearly two months of berthed operations, with the craft currently set to depart the international outpost on 15 July 2018. However, during this berthed period, Cygnus will do much more than just deliver cargo to the Station.
For the first time since the retirement of the Space Shuttle fleet in July 2011, a U.S. spacecraft holds the potential to perform a reboost of the International Space Station’s orbit. The reboost – in this case – would be small and negligible, classed officially as a Detailed Test Objective in which Cygnus will fire its main engine for just a few seconds to demonstrate its capability to perform more robust ISS orbit raising maneuvers in the future.
“We actually started engaging NASA on this topic in the fall of last year,” said Mr. DeMauro. “We have a large engine on the back of the spacecraft that puts out a lot more thrust [than the 32 maneuvering thrusters on Cygnus], and this is the engine we use for orbit raising burns.
“And so we started talking with NASA at the program office about the possibility of Cygnus providing some form of orbit raising capability using that engine. And one of the things we decided to do earlier this year is to put this Detailed Test Objective in place and at least work through the process of seeing if we could get that approved by NASA and of course specifically the safety review panel.”
The NASA program office showed great interest in this potential capability from Cygnus, and NASA and its safety office have been moving through the process of performing the various analyses needed to ensure that using Cygnus while berthed to the Node-1 nadir port to reboost the ISS does not impart dangerous thrust loads onto the structure of the Station.
“If we’re going to be imparting thrust or forces on the ISS by thrusting our engine, [NASA] has to do work on their side, and they’ve done that,” noted Mr. DeMauro. “As far as if it’s going forward, we expect it to go forward. We are waiting for the final sort of dot the Is and cross the Ts with the safety panel, but we don’t expect any issues closing that all out.”
If the Detailed Test Objective receives final clearance to proceed, Orbital ATK anticipates performing this test in the latter part of Cygnus’ mission at the ISS. Assuming this test is successful, Orbital ATK hopes to offer this capability to NASA on future Cygnus missions both as part of the extended CRS1 and upcoming CRS2 contracts for cargo resupply of the orbital lab.
If for some reason the Detailed Test Objective cannot be accomplished on this mission, Orbital ATK will simply move the test to the following flight of Cygnus later this year.