Northrop Partners With DARPA To Build Robotic Satellite Servicer

Hard on the heels of its first Mission Extension Vehicle (MEV) docking with a client satellite in geostationary orbit, Northrop Grumman subsidiary SpaceLogistics has signed on as DARPA’s commercial partner for the Robotic Servicing of Geosynchronous Satellites (RSGS) program.

The role became available in January 2019, when Maxar Technologies’ subsidiary SSL withdrew as DARPA’s commercial partner, citing financial pressures.

• DARPA to supply robotic payload for MRV servicer
• MRV will build on Northrop’s life-extension MEV

Under the agreement, DARPA will provide the robotics payload for Space-Logistics’ Mission Robotic Vehicle (MRV), already planned as its next step in satellite servicing after the MEV. The company will provide the spacecraft bus, launch and operate the MRV during its on-orbit demonstration for DARPA, then continue to own and operate the robotic servicer in geostationary orbit (GEO)—providing services to commercial and government customers.

The MRV bus will leverage the MEV, which is designed to attach itself to a client satellite and extend its operational life in GEO by up to five years. The MEV, in turn, is based on Northrop Grumman’s GEOStar commercial satellite bus.

Northrop’s first MEV docked with Intelsat’s IS-901 satellite just outside GEO on Feb. 25. Once attached, MEV-1 took over position and attitude control of the satellite and is now moving it back to GEO, where it will resume service.

A second servicer, MEV-2, is to be launched this year to dock with a second Intelsat satellite in GEO. On completion of their initial five-year missions, MEV-1 and -2 will undock and are expected to provide life-extension services to other satellites for another 10 years, SpaceLogistics says.

Meanwhile, Northrop has begun development of the Mission Extension Pod (MEP), a smaller and less expensive propulsion module that the MRV will attach to a client spacecraft. The MEP performs orbital control only for up to five years but remains attached permanently to the satellite.

The DARPA-supplied payload for the MRV, developed and integrated by the U.S. Naval Research Laboratory, comprises two dexterous robotic manipulator arms along with multiple sensors and several interchangeable tools.

RSGS plans to demonstrate rendezvous, inspection, repair, reconfiguration, refueling and relocation of a cooperating GEO satellite. “The new robotics technology on this mission advances our vision to build a fleet of satellite-servicing vehicles that provide customers with a variety of options to select the type of life-extension or in-orbit repairs they need,” says Tom Wilson, president of SpaceLogistics.

Northrop and Intelsat hailed the autonomous docking of MEV-1 with IS-901 as “historic.” After launch by a Proton rocket in October from Baikonur, Kazakhstan, the servicing spacecraft used its electric propulsion to raise its orbit, while IS-901 was moved to a graveyard orbit 300 km above GEO. 

On Feb. 1, the MEV-1 arrived in the same orbit as IS-901 and began maneuvering to rendezvous and dock with the satellite. The servicing spacecraft began a series of approach maneuvers during which Northrop tested and tuned the visual, infrared and lidar sensors used for rendezvous and docking.

By Feb. 24, the distance between MEV-1 and IS-901 had been reduced to 80 m (260 ft.), and in the early hours of Feb. 25, the spacecraft approached to its final waypoint. There, it awaited permission from ground control to proceed, says Joe Anderson, vice president of operations and business development for SpaceLogistics.

Mission control gave the command to dock and MEV-1 autonomously inserted its docking probe into the nozzle and through the throat of IS-901’s liquid apogee engine. The probe deployed a capture mechanism and then retracted, pulling stanchions on the servicer up against the satellite’s launch adapter ring and securing the spacecraft together.

The servicing spacecraft then took control of IS-901’s position and attitude, reorienting the satellite back toward Earth within a few seconds, Anderson says. The MEV-1’s propulsion system is now moving the combined spacecraft back to geosynchronous orbit, where it is expected to resume customer service by late April or early May, says Intelsat CEO Stephen Spengler.

Northrop declines to reveal the cost of MEV-1, but IS-901 had only months of fuel remaining and Intelsat “saw a solid business case to use the service to extend the customer service life of IS-901 for another five years,” Spengler says. “The economics made sense for us in terms of revenues generated and capital investment deferred.”

Services were shut down, and IS-901 was moved to graveyard orbit as a safety precaution before the rendezvous with MEV-1, but the transient effects observed during docking of the two spacecraft were “much less than simulated,” says Jean-Luc Froeliger, vice president of space systems engineering and operations at Intelsat.

Due to the low transients, during the next mission the satellite will not be moved to graveyard orbit for its docking with MEV-2. It will instead remain in its operational GEO location providing uninterrupted service to customers, he says.

The feat has excited at least one potential customer: the U.S. Defense Department. “To take a satellite that was at end-of-life and have another satellite take control of it and give it new life—that has opened up a lot of thinking for us,” says John London, chief engineer for space and strategic systems at U.S. Army Space and Missile Defense Command.

“We are now looking at ways that we can repurpose not just communication satellites but other satellites that are at end-of-life—or given up for dead—and finding ways to reuse them, maybe in different ways,” he says.

Satellite manufacturer Airbus is less certain of the value. “We had our own activity, which we called the SpaceTug. We stopped it at the preliminary design review at the end of 2018. The technology was feasible, but we had significant questions about the business case,” 

Oliver Juckenhoefel, Airbus senior vice president of on-orbit services and exploration, told reporters at the Satellite 2020 show.

“In 2017, when we started these initiatives, there was so much confusion in the market. Companies were interested in temporarily prolonging the life of satellites to avoid having to make an investment decision,” he says.

“We don’t know whether there will be a market or not. Northrop seems to be convinced, and I like that very much. We are not investing our own money because we don’t see a commercial market, but we believe we need to be prepared,” Juckenhoefel says.