WASHINGTON — A long-delayed NASA ozone mapping instrument is undergoing testing and is slated to fly to the international space station in 2014 aboard a Falcon 9 rocket that also will deliver supplies to the orbital outpost.
The 76-kilogram Stratospheric Aerosol and Gas Experiment 3 (SAGE 3), which has spent the past nine years stored in a shipping container at NASA’s Langley Research Center in Hampton, Va., was built to fly on the space station as early as 2005. That plan was scrapped, however, when NASA altered the design of a logistics palette needed to mount the SAGE 3 instrument on the station’s Earth-facing exterior.
NASA now plans to refurbish SAGE 3 before launching it to the orbiting platform in June 2014 inside the unpressurized trunk of a Dragon capsule during a routine resupply run atop a Falcon 9 rocket. Both vehicles are built by Hawthorne, Calif.-based Space Exploration Technologies (SpaceX).
Michael Cisewski, SAGE 3 project manager at Langley, said the space station’s robotic arm will attach the instrument and a specially designed nadir viewing palette to an ExPRESS Logistics Carrier platform already aboard the station.
“Both of them will ride up in the Dragon trunk, Dragon will go ahead and berth with the space station and the robotic arm will bring out the nadir viewing platform and install it, and then come back and get the SAGE payload and install it onto the nadir viewing platform,” Cisewski said in a March 24 interview.
Previously SAGE 3 was to be mounted on a Brazilian-built platform, but the hardware was never delivered to NASA , forcing the agency to put the instrument on ice.
Since coming out of storage in June 2009, SAGE 3 has undergone a series of assessments at Langley. In mid-February the instrument was tested in various solar and lunar operational modes, allowing engineers to make minor modifications to the instrument. Cisewski said the effort has benefited from participation by NASA personnel who worked on SAGE 3 before it was shelved.
“We’ve been successfully able to pull some of the people that worked on it before, so there are people [involved] who are familiar with SAGE 3 from when we initially developed it and we initially looked at flying it on the space station,” he said.
In 2009, NASA awarded Boulder, Colo.-based Ball Aerospace & Technologies a contract worth up to $9.7 million over five years to assess and possibly refurbish SAGE 3. Ball built three copies of SAGE 3, the first of which flew aboard a Russian Meteor-3M satellite launched in 2001. That instrument stopped working in 2006 when a power failure cut off communication with the spacecraft. The third SAGE 3 instrument, which served as the original Meteor 3M flight model, was disassembled to diagnose a problem with the azimuth drive system. Cisewski said the instrument subassemblies are currently in storage.
The first SAGE instrument launched in 1979, and was followed by SAGE 2 in 1984. SAGE 2 gathered data for more than 20 years, making it one of NASA’s longest-running Earth observing missions.
Cisewski said that in addition to ongoing technical assessments and in preparation for requalifying the instrument, NASA is in talks with the European Space Agency (ESA) to refurbish a hexapod built by Thales Alenia Space of France and Italy to keep the SAGE 3 pointing in the right direction as the space station maneuvers.
“We’ve had discussions with ESA about utilization of the hexapod for this mission and we’re in the process of securing that commitment,” he said. “It’s currently being stored in Italy. We’re going to have the Europeans recertify it for flight and we’ll have it delivered here and integrate it for the mission.”
Cisewski said Langley also plans to build an avionics box to provide a communications link among SAGE 3, the hexapod and the space station.
“All of those activities will be complete and we will have the palette and the cable harnesses and everything we need here by August of 2013,” he said, adding that once integration and testing are complete, the full-up unit will be delivered to NASA’s Kennedy Space Center, Fla., in March 2014.
Cisewski said the space station offers unique benefits to the SAGE 3 mission, including its inclined orbit around the Earth.
“Because the station orbit is an inclined orbit, we get quasi-global measurements, so we cover the mid-latitudes,” he said. “The station orbit is really a big advantage. If we had a choice to fly in an inclined orbit we would absolutely pick that every time.”
However, Cisewski said there are some challenges to flying SAGE 3 on the space station rather than a free-flying satellite.
“Some of that is that the station flies a bit of a lower altitude that’s beneficial for some things, but the attitude stability is not the same as you would have on a free-flying satellite,” he said. “That’s why we need the hexapod, if you have visiting vehicles and things like that, so the configuration can kind of change, whereas on a free-flying satellite once you launch it that’s the configuration that it’s going to be in forever.”
NASA plans to operate the instrument through the end of the decade, Cisewski said. “We’re looking at what the future holds and when we would fly [another] SAGE, and we’re having those discussions right now,” he said.
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