As the International Space Station nears completion, NASA and international agencies are ramping up scientific utilization of the outpost, particularly in fields of Earth science.

Credit: NASA

Although basic research has been conducted aboard the outpost since 2000, the addition of new laboratory facilities and a six-person crew are greatly expanding the station's science capacity and broadening the scope of experiments hosted by the complex.

"Assembly is nearly complete and research is really taking off in lots of new directions. We're at the point now where we can take full advantage of the International Space Station for all the uses it was intended for. It has great access to the space environment for investigators, ample power and telemetry for the data to come down, and also to use as a facility for pathfinder or engineering testbed for new activities," said John Uri, NASA's lead scientist for the station program.

Station residents now spend an average of about 40 crew hours per week on research, up from less than 15 hours before the expansion to a six-person crew in May, Uri said.

The station's NASA, European and Japanese labs are now home to 21 refrigerator-sized internal experiment racks. More pressurized payloads are due for delivery next year.

Eighteen power and data ports for large external experiments have already been delivered to the complex's U.S., European and Japanese segments. Ten sites are available on Japan's Kibo laboratory module's exposed facility, and four locations each are located on the European Space Agency's Columbus lab and two ExPRESS logistics carriers brought to the station during the shuttle Atlantis' recently-completed mission.

Two more ExPRESS carriers are scheduled for launch to the station next year, adding four more experiment sites.

Other experiment platforms are on the outpost's Russian segment.

Uri said Earth observation, astrophysics, solar science and materials research payloads could use the exposed sites.

The demand for research on the station is still unclear, and officials could not predict if all the exterior ports would ever be occupied, especially given serious concerns that the space shuttle's retirement will limit opportunities for future experiment deliveries.

In addition to a set of smaller experiments, six instrument packages are currently operating outside the station: a materials science investigation called EuTEF, the SOLAR platform to study the sun, a space environment monitoring system named SEDA-AP, the MAXI all-sky X-ray scanner, the SMILES ozone experiment, and another Earth science payload called HREP.

EuTEF and SOLAR are mounted on Columbus, while the other four experiments are attached to Kibo's exposed facility.

SMILES and HREP opened a new chapter in the station's life when they arrived in September. They are the first large Earth observation payloads operating aboard the orbiting lab.

Both science packages were carried to the station on Japan's H-2 Transfer Vehicle. The Japanese space agency, or JAXA, developed the SMILES experiment and NASA sponsored the HREP payload.

SMILES stands for the Superconducting Submillimeter Wave Limb Emission Sounder, a super-cold instrument built to detect faint atmospheric signals containing information on the health of the ozone layer and concentrations of trace gases.

Scientists expect SMILES will help computational models gauge the recovery of the ozone layer after damage attributed to human activity.

HREP includes a pair of experiments, named HICO and RAIDS, from the U.S. Naval Research Laboratory. HICO is a hyperspectral imager to collect detailed pictures of the world's coastal oceans, and RAIDS is studying the temperature of the lower thermosphere.

HICO imagery of Midway Island. Credit: NASA

HICO imagery is taken in 128 spectral bands, providing new insights of coastal oceans for commercial maritime and military operations. Applications for RAIDS data include predicting atmospheric drag on orbiting objects and forecasting outages of the Global Positioning System, according to researchers.

"We often overlook that, in addition to great pressurized facilities for life and microgravity sciences, given its orbital inclination and altitude, the space station is a great platform for conducting Earth observation and remote sensing, covering roughly 95 percent of the world's populated areas," Uri said.

The complex circles Earth at an altitude of more then 200 miles in an orbit that takes the station over latitudes of 51.6 degrees on both sides of the equator.

Critics have oftened cited the station's orbit as unsuitable for most Earth observation investigations. Remote sensing payloads usually operate in near-polar sun-synchronous orbits, which allow imagers to rapidly revisit locations on the planet with the same sun angle, providing identical viewing conditions.

"Most people doing Earth imaging like sun-synchronous orbits, but we're a demonstration project," said Mike Corson, principal investigator for the HICO experiment. "The traditional sun-synchronous orbit is designed so that everytime you pass over a scene, the sun is in the same place and you're viewing it in the same way, so you can't test out limits of applicability. We can."

Corson and Scott Budzien, chief researcher for the RAIDS experiment, said the space station has advantages that could attract some Earth science payloads.

The complex can support more massive experiments than free-flyer satellites, giving researchers more flexibility in designing imaging instruments.

"The frequent flights and the large cargo capacity of the vehicles traveling to the space station can accommodate the heavy science payload that we built," Budzien said.

HICO was able to employ commercial off-the-shelf components instead of more expensive, smaller parts, thanks to the capabilities of the space station.

SMILES uses an innovative superconducting mixer to chill its sensor to -450 degrees Fahrenheit. The technology draws a high volume of electricity from the station's power system.

"The big advantage of ISS for this experiment is a big power supply and continuous data handling, which enables us to test out these new technologies in space. As a result, SMILES can precisely measure trace gases," said Naoki Nagai, deputy director of JAXA's office in Houston.

RAIDS also benefited from using the station platform, especially in balancing requirements in power, mass, data handling, schedule and budget, according to Budzien.

"Because the space station offers relatively plentiful power, mass and size constraints, that has really relaxed the situation so our engineers could concentrate on optimizing our science and delivering this payload for flight in a very short period of time," Budzien said.

Experiments mounted on the Japanese Kibo exposed facility. Credit: NASA

NASA's fleet of tracking and data relay satellites provide near-continuous communications coverage of the space station's orbit, giving experiments on the complex more chances to beam data back to researchers on Earth.

"The ISS provides real-time data and real-time commanding of our instruments, and this is a real novelty to us," Budzien said.

ESA space station officials issued a call for ideas in October to institutions interested in developing climate change experiments for the complex between 2012 and 2020.

"Potentially, the ISS can be used as an observation platform for instruments and experiments relevant to global change studies, supplementing ongoing and planned observations from dedicated platforms," ESA said in the announcement.

The call for ideas was released with the help of ESA's Earth observation programs directorate.

"I cannot forecast the outcome," said Volker Liebig, director of ESA's Earth observation programs. "ISS could be a platform to demonstrate and test new technologies and instruments."