Published online 20 January 2011 | Nature | doi:10.1038/news.2011.32

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NASA goes for Glory

Mission to monitor solar energy and aerosols set to join 'A-Train' of climate satellites.

Glory satelliteInstruments on Glory will help researchers understand Earth's overall energy budget.NASA

NASA is preparing to launch an environmental monitoring satellite designed to maintain and bolster a continuous record of solar energy, while providing new details about aerosols, which reflect and absorb the Sun's rays passing through the atmosphere.

The Glory mission is scheduled to launch on 23 February aboard a four-stage Taurus XL 3110 rocket from Vandenberg Air Force Base in California. Once in space, Glory will join the Afternoon Constellation, or A-Train — an ensemble of satellites studying changes in Earth's climate system.

The A-Train, which orbits some 700 kilometres above Earth, travels at a speed of more than 24,000 kilometres per hour — managing a full orbit every 100 minutes to map the Earth roughly once every 16 days. There are currently four satellites in the ensemble.

Glory itself carries two scientific instruments. The Total Irradiance Monitor faces the Sun to measure its energy output — data then used to calculate, on an area basis, the total solar energy entering the Earth's atmosphere. The Aerosol Polarimetry Sensor points towards Earth and studies atmospheric aerosols.

Both instruments will help scientists to better understand Earth's overall energy budget, says Hal Maring, project scientist for the Glory mission at NASA headquarters in Washington DC. "This really is a climate mission," Maring says. "We've got to know how much energy is coming in, if it's changing and how that energy affects the climate system."

Beyond the SORCE

The monitor, built by the University of Colorado's Laboratory for Atmospheric and Space Physics in Boulder, is a second-generation instrument designed to extend a continuous record of space-based measurements dating back to 1978. Those data have proved critical as scientists try to gauge how the 11-year solar cycle and other smaller fluctuations affect Earth's climate. The monitor is roughly three times more accurate than its predecessor aboard the Solar Radiation and Climate Experiment, known as SORCE.

The sensor, built by Raytheon Space and Airborne Systems in El Segundo, California, will analyse the way airborne particles reflect and absorb light. Collecting data at nine wavelengths — from the visible to the near-infrared regions of the electromagnetic spectrum — the sensor will provide highly accurate estimates on the quantity and to a certain extent the location of aerosols in the atmosphere.

And, by analysing the polarization of light, which is highly dependent on the micro-physical properties of the particles, scientists should have a better idea of whether they are looking at disc-like particles of dust, crystal-shaped salts or spherical particles of sulphate pollution.

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Although the aerosol sensor provides a measurement only of the total aerosols in a given column of air and cannot pinpoint their exact location, it will be flying with a suite of other instruments in the A-Train that can help to fill those gaps and extrapolate the data to a broader volume of the atmosphere.

"The data will be important, there's no question," says John Seinfeld, an expert on aerosols at the California Institute of Technology in Pasadena. Aerosols are one of the largest areas of uncertainty in Earth's climate system, he says, "and the Glory aerosol instrument will provide key data to improve our knowledge of the quantity and type of aerosols worldwide".

Once Glory goes up next month, NASA will turn its attention to Aquarius, a joint effort with Argentina's National Space Activities Commission to measure salinity levels throughout the world's oceans. Aquarius is scheduled to launch in June, but not as part of the A-Train. 

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