Japan’s HTV Delivered U.S. Navy Experiments to Station

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WASHINGTON — A pair of experimental instruments built by the U.S. Naval Research Laboratory were delivered to the international space station aboard Japan’s H-2 Transfer Vehicle (HTV) in mid-September where they will monitor space weather and map the Earth’s coastal regions.

NASA’s program scientist for the international space station, Julie Robinson, said the newly activated suite of sensors comprises the most complicated Earth observation instrument currently in service aboard the orbital outpost.

Launched Sept. 10 aboard the HTV cargo tug from Tanegashima Space Center in Japan, the dual-experiment payload arrived at the station Sept. 17 and was later deployed to an external payload platform astronauts added to the outside of the Japanese Experiment Module, Kibo, this past summer.

One of the payload’s two instruments, the Hyperspectral Imager for the Coastal Ocean (HICO) was designed and built by the Naval Research Lab’s Remote Sensing Division under a fast-paced 16-month program. Project officials say it is the first spaceborne hyperspectral imager optimized for characterization of the coastal environment.

The second instrument is the Remote Atmospheric and Ionospheric Detection System (RAIDS). Built by the Naval Research Lab’s Space Science Division in cooperation with the Los Angeles-based Aerospace Corp., RAIDS is a hyperspectral sensor suite for global remote sensing of the Earth’s ionosphere and thermosphere.

Together, the experiments will provide the first-ever high-quality and real-time monitoring of space weather and coastal ocean environment from the orbiting lab. Although space station astronauts frequently photograph the Earth using handheld cameras equipped with powerful lenses as part of NASA’s Crew Earth Observation program, Robinson said the two Pentagon-funded experiments are the most sophisticated observation sensors currently operating on the station. A NASA-funded imager called AgCam — short for Agricultural Camera — was added to the space station in 2008 to take frequent looks at vegetated areas on Earth, specifically focusing on the northern Great Plains and Rocky Mountain regions of the United States. Software problems, however, have rendered the imager idle.

Design and development of the HICO and RAIDS instruments for the station began in 2007 when the Defense Department’s Space Test Program administered by the U.S. Air Force Space and Missiles Systems Center in Los Angeles approached the Naval Research Lab with a proposal to develop an experimental payload that could be ready for HTV integration in a little over a year.

“On the HICO side, we gulped, but did our best to take advantage of this wonderful opportunity,” said Mike Corson, the Naval Research Lab’s principle investigator for the coastal imaging project.

Funded by the U.S. Office of Naval Research through its Space Innovative Prototype program, HICO is the first type of spectral imager optimized for scientific investigation of the coastal ocean and nearby land regions. Corson said the one-year experiment is designed to capture data across all four seasons related to on-shore vegetation, and water clarity and depth, among other attributes. Corson said the Defense Department, and the Navy and Marines in particular, are interested in complex coastal properties that can influence operational decision-making on the ground.

“Water clarity bears on how well a diver can see in the water,” he said, “Or the bathymetry maps … on the trafficability of small craft.”

Corson said HICO’s imagery will be streamed from the space station to the NRL Remote Sensing Division here before going to the NRL Oceanography Division at Stennis Space Center in Hancock County, Miss., for archiving and distribution to other government entities and collaborative universities. Corson said the National Oceanic and Atmospheric Administration and National Geospatial-Intelligence Agency also are logical users of HICO imagery.

RAIDS, meanwhile, combines a suite of eight optical instruments designed to study the Earth’s thermosphere and ionosphere using hyperspectral limb scanning, according to Scott Budzien, NRL’s principle investigator for the experiment. He said the payload will gather data continuously, transmitting it in real-time, allowing live monitoring of the upper atmosphere for more accurate space-weather forecasting.

Budzien said RAIDS is a basic research capability that could improve the Defense Department’s ability to track orbital debris.

“As the atmosphere heats up due to solar wind or solar flares, it expands, causing drag on satellites and space junk to increase,” he said. “And that causes tracking problems for radar systems and folks that have to track all of that space junk.”

Budzien said the RAIDS experiment, based on an existing hardware design intended for another mission on a sun-synchronous satellite, was adapted to utilize characteristics of the space station.

“One of the features we gain by going to the space station is that because the station is at a lower altitude, it brings us closer to the lower part of the thermosphere, and gives us better spatial resolution because it’s closer to what we’re looking at,” he said. “And by not flying it on a sun-synchronous satellite, it allows us to sample a whole range of times of day.”

In addition, he hopes the instrument will demonstrate advanced remote-sensing techniques that could lead to follow-on capabilities in an operational environment, including new ionospheric sensors and new ways to measure the temperature of the upper atmosphere.

Budzien said the RAIDS data will be distributed to “pretty much anybody in the scientific community who is interested,” including a number of universities that already partner on the project.

Budzien said the Naval Research Laboratory appreciates the opportunity to be the first to fly U.S. scientific payloads aboard the HTV.

“One of the biggest challenges was being the first one,” he said. “We were the first American payload going through this process, and a lot of the work has been learning the best ways to negotiate the requirements of [the Japan Aerospace Exploration Agency] and NASA and all of the various agencies.”

The HTV is nearly 4.5 meters in diameter, stands over 9 meters tall and is capable of hauling some 6 tons of pressurized cargo to the space station. When flown with an unpressurized segment, the HTV can carry even more gear.

Budzien said the HTV’s accommodating payload capacity helped make it possible to develop RAIDS on such a short schedule.

“That really facilitated the development of this program, the fact that they could accommodate a great deal of mass for this experiment,” he said.

Corson said the work they have done will pave the way for integration of future payloads aboard the Japanese transfer vehicle, and could prove especially useful after NASA retires its aging space shuttle fleet next year.

“[It’s] potentially a real workhorse for taking future payloads to the station,” he said. “I’m not speaking for NASA, but shuttle is at risk of being phased out in the fairly near future, so there is certainly an interest in finding other vehicles that can launch payloads to station.”