Artist rendering of SpaceX Dragon spacecraft berthing to nadir Common Berthing Mechanism on the Harmony module of the International Space Station. (NASA)
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The ExPRESS Pallet Adapter is the platform that SAGE III that will mount to the International Space Station, shown here during vibration testing at NASA's Langley Research Center in preparation for a 2014 launch date. (NASA/Sean Smith)
View large image About 428 miles above Earth, the collective observations from the "A-Train," or Afternoon Train build three-dimensional images of the Earth's atmosphere and surfaces. A team at NASA's Langley Research Center in Hampton, Va., is working to supplement those satellites with an instrument mounted to the orbiting International Space Station, or ISS.
According to Richard Eckman of the Earth Science Division of the Science Mission Directorate at NASA Headquarters in Washington, the satellites provide a means to make near simultaneous measurements of atmospheric processes.
NASA's Stratospheric Aerosol and Gas Experiment, or SAGE III on ISS, team intends to strengthen those measurements by providing important aerosol information concerning particles in the air, such as clouds or air pollution and other atmospheric gases, which are not currently captured. The space station's orbital inclination also provides an ideal view for consistent ozone measurements.
By combining data from SAGE III with data from the Atmospheric Chemistry Experiment, or ACE, a satellite mission on board the Canadian satellite SCISAT-1, a unique data set about the tropopause, the atmospheric boundary between the troposphere and the stratosphere where an abrupt change in environmental lapse rate usually occurs, will become available.
"The tropopause region needs to be fully explored," said Joe Zawodny, SAGE III on ISS project scientist. "ACE and SAGE III on ISS are going to fly concurrently and what we can do with that data is very exciting. We can produce a backbone of international analysis."
Getting Ready for Launch
The SAGE III on ISS team is getting its instruments ready for a scheduled 2014 launch by following a rigorous testing and review schedule. In the fall of 2012, four engineering development components of SAGE III passed vibration testing at NASA Langley. Starting in January, the team began testing flight hardware. Those tests will continue through to launch.
After the project's Critical Design Review, scheduled for February 2013, the team will build additional flight hardware and complete refurbishment of existing equipment. All the pieces are scheduled to be ready for integration and testing in August 2013. After flight component tests are complete, the team will begin the launch-ready process.
Arrival to the International Space Station
SAGE III on ISS is set to launch on a SpaceX Falcon 9 rocket from NASA's Kennedy Space Center. Upon arrival to the space station, the crew will install the instrument onto an ExPRESS Logistics Carrier, or ELC, platform. It will take as long as 30 days to move the payload from the Falcon 9's Dragon truck and install it on the ELC. It will take another 30 days after installation for outgassing and to establish thermal control.
After a series of calibrations and check-outs, and an on-orbit acceptance review, SAGE III will begin taking measurements. The data is downloaded to the ground daily for use by the international science community.
"We are making great progress," said Mike Cisewski, SAGE III on ISS project manager. "It is important to extend the SAGE data record for the science community."
Why Do We Need Measurements from Space?
Like its predecessors SAGE I and II, which collected aerosol data from 1979 to 2005, SAGE III on ISS will measure aerosols, ozone, water vapor and other gases in Earth's atmosphere. According to Zawodny, it is an important time to study atmospheric gases, which help to shield everything on Earth from the sun's harmful ultraviolet rays. Scientists say that the protective ozone layer appears to be recovering and by 2015, it could be restored at least half way back to the initial protective layer that was observed in the late 1980s.
"Greenhouse gases and aerosols can be measured from the ground, but if you want to determine trends accurately, you have to capture it all," Zawodny said.
The complete data that SAGE III on ISS can provide will help to assess the state of recovery in distribution of the ozone, reestablish aerosol measurements needed by climate and ozone models, provide further insight into processes and trends, and predict global warming.
Once measurements begin, the science data will be assessed by the newly formed Science Utilization Team led by Pat McCormick of Hampton University in Hampton, Va. The ISS is expected to operate through at least 2017.