NASA Ready To Put Robotic Refueling to the Test

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WASHINGTON — The NASA Goddard Space Flight Center team that engineered five successful in-space servicing missions to the flagship Hubble Space Telescope is preparing for a ground-based satellite refueling demonstration next April that will include nearly every constraint the team would face if it tried to robotically service an operational satellite.

The demo, part of a project known as Restore, will be a “full-up, bring-it-all-together” test staged in a converted clean room at Goddard’s Building 29, according to Benjamin Reed, deputy project manager for the 40-person Satellite Servicing Capabilities Office at the Greenbelt, Maryland-based NASA field center. The team, led by veteran robotics wizard Frank Cepollina, was formed after the final Hubble servicing mission in 2009 in order to preserve the expertise and capabilities Goddard developed during nearly two decades of supporting astronaut repair calls to the orbiting telescope.

In the Restore demo scheduled for April, the Satellite Servicing Capabilities Office will take over the same room that once housed the Global Precipitation Measurement satellite, the largest spacecraft ever assembled at Goddard. Reed and his team will stack a dummy satellite above a space-capable robotic satellite servicing craft and, using time-delayed remote control to simulate communications lag from orbit, attempt an end-to-end refueling mission.

The servicing craft will have to cut through the dummy satellite’s thermal blanket, remove a fuel cap that was designed never to be removed, and pipe fake satellite fuel through lines pressurized to roughly 17 kilograms per square centimeter — about the same pressure the servicing robot would encounter refueling an operational satellite.

Unlike February’s Remote Robotic Oxidizer Transfer experiment, in which Goddard operators remotely commanded a robot at the Kennedy Space Center in Florida to pump corrosive, explosive oxidizer into a pressurized fuel tank, the Restore demo on the slate for April will not involve toxic fluids. However, it will use a space-capable robot designed to function in microgravity, and not the heavy, industrial robotic arm used in the remote control experiment this year.

The Satellite Servicing Capabilities Office is trying to figure out how to prolong the life of operational satellites that have working instruments but empty fuel tanks. It is an old idea that has yet to catch on either in the public or private sector, but it has the full support of Sen. Barbara Mikulski (D-Md.), chairwoman of the Senate Appropriations Committee and Goddard’s guardian angel.

Mikulski steered $100 million to the office for 2014, which was reduced to $74 million in NASA’s operating plan, agency spokeswoman Adrienne Alessandro said in a July 17 email. This year, the senior senator from Maryland prescribed $130 million for the office as part of a 2015 spending bill that stalled after clearing the Senate Appropriations Committee in June.

However, months before the Senate Appropriations commerce, justice, science subcommittee, which also is chaired by Mikulski, proposed a raise for the Satellite Servicing Capabilities Office, there were signs the Obama administration and the senator were not seeing eye-to-eye on satellite servicing.

When the White House released its 2015 budget request in April, it proposed moving funds for the Satellite Servicing Capabilities Office out of the international space station program’s nearly $1.5 billion systems operations and maintenance budget and into a roughly $300 million ISS research budget.

The White House also wants to rename the office “In Space Robotic Servicing” and give its activities a more general-purpose slant that could “enable multiple NASA missions, including servicing potential science satellites, non-NASA users, and providing robotic tools for an Asteroid Redirect Mission, as well other applications for use and/or testing on ISS.”

This, according to the report accompanying the stalled 2015 spending bill, “highly frustrated” Senate appropriators, who fumed that NASA’s “most senior leadership” had failed to embrace satellite servicing as a “transformational ap­proach to managing the Nation’s governmental space assets.” The report said the agency should disregard the White House’s plan and continue work on “a Restore Pathfinder mission to be achieved no later than 2017 and which may be used for either a low-earth orbit or geostationary orbit servicing of government assets only.”

The bill report, which is in limbo along with the bill itself, also said NASA’s 2016 budget should include a “full program of record on satellite servicing that includes technology development, the Re­store Pathfinder, and recommendations for a Restore follow-on mis­sion.”

Of the 40 people now working in the Satellite Servicing Capabilities Office, about 30 have been there since 1994, when the office was still known as the Hubble Space Telescope Flight Systems and Servicing Project. About half a dozen of the team’s most veteran technicians, including Cepollina, have been with the office since 1984, when it was known as the Satellite Servicing Project, Alessandro told SpaceNews.

The team’s focus in the early 1980s was much the same as it is now: to develop tools and plans for servicing operational spacecraft. Members cut their teeth on the Solar Maximum Mission, a heliophysics satellite that launched in 1980, malfunctioned in 1981, and had to be repaired in 1984 by the crew of the Space Shuttle Challenger. Astronauts captured the satellite and maneuvered it into the shuttle’s payload bay for repairs. Unlike the spacecraft the Satellite Servicing Capabilities Office wants to work with these days, Solar Maximum was designed to be serviced.

Meanwhile, in Space …

As recently as 2012, the Satellite Servicing Capabilities Office was considering a repair mission to the Tracking and Data Relay Satellite (TDRS)-9, which launched in 2002. The satellite is part of the geostationary communications-relay constellation NASA uses to communicate with the international space station and other spacecraft in low Earth orbit.

TDRS-9 was launched in 2002 and continues to operate despite low pressure in its fuel system that has slowed its maneuvering capability. Alessandro said a mission to refuel TDRS-9 was still possible but not currently planned. Another real-life target that caught the Satellite Servicing Capabilities Office’s eye was GOES-12, but the National Oceanic and Atmospheric Administration took it out of the running when it decommissioned the 12-year-old geostationary weather satellite last year.

Although not as ambitious as topping off one of the primary U.S. weather satellites or repairing a NASA communications spacecraft, the Goddard robotics office has already completed a few on-orbit demos and is planning more.

At the international space station since 2013, specialized Goddard-built satellite servicing tools fitted to the station’s Canadian-built robotic arm have helped ground operators at the Johnson Space Center in Houston — directed by the team at Goddard — transfer an ethanol-based satellite fuel stand-in from one reservoir to another as part of the Robotic Refueling Mission.

In these tests, ground controllers poke and prod Goddard-made dummy satellites known as test boards, which were brought to station by the space shuttle and Japan’s H-2 Transfer Vehicle. The test boards are mounted to a platform on one of the station’s Earth-facing trusses. There are three of these boards on orbit now, and a fourth launched to the orbital outpost July 29 aboard Europe’s Final Automated Transfer Vehicle.

Also along for the ride on the European cargo freighter is a brand new satellite servicing attachment known as the Visual Inspection Poseable Invertebrate Robot (VIPIR): a flexible 90-centimeter-long boroscope equipped with a camera and lights that will help ground operators see what they are doing when they approach a serviceable satellite for the first time.

It is not clear when that tool will first be tested on-orbit, Reed said. Resources are at a premium on the station, including the time it will take to have a controller at the Johnson Space Center install the new VIPIR-specific servicing taskboard on the station’s exterior using the Canadian arm.

Setup could happen either later this summer or early this fall. After that, the station’s “tremendously complex schedule program,” makes things harder to predict, Reed said.

“We will wait for our turn in line to get those activities scheduled,” he said.