This collection of images shows Saturday's Pegasus mission from takeoff of the L-1011 to launch of the rocket. Photos: NASA TV/Spaceflight Now

Cruising about 39,000 feet above the open waters of the Atlantic, an air-launched Pegasus rocket was dropped from the belly of a carrier jet Saturday afternoon to blast a science satellite into orbit to study the Sun's influence on Earth's environment.

After taking off from the Cape Canaveral Air Force Station's Skid Strip runway, the modified L-1011 aircraft flew off the east coast of Florida, battling a stiff tailwind to release the winged Pegasus at the prescribed location.

At around 3:13:35 p.m. EST (2013:35 GMT), the pilot aboard the "Stargazer" jet pushed a button to cast free the Orbital Sciences-built rocket. The 55-foot long, 50,000-pound booster fell for five seconds before its first stage solid-fuel motor ignited.

About 11 minutes later, the NASA's Solar Radiation and Climate Experiment satellite was successfully deployed into low-Earth orbit from the rocket's third stage, completing the 32nd Pegasus mission since 1990, the 22nd for the stretched "XL" version of the launcher and the first in nearly a year.

Controllers established contact with SORCE within seconds, confirming the Orbital-built satellite was alive.

"Everything is wonderful," NASA Launch Manager Omar Baez proclaimed.

"Today's successful launch adds to our constellation of Earth-viewing satellites that help us to understand and protect our home planet," said Ghassem Asrar, NASA's associate administrator for Earth Sciences.

The $122 million SORCE mission is supposed to last five years -- though scientists hope it will last much longer -- to measure how the radiation streaming from the Sun affects the Earth's atmosphere and climate.

"For more than 40 years, NASA has been involved in studies of the Earth's environment from space. The SORCE contribution will be to try to improve our understanding of the amount of solar energy that comes into the Earth's environment," explained SORCE Program Manager Donald Anderson.

"This mission will help to distinguish between natural and human-induced influences in climate change," Asrar said. "Incoming light energy from the Sun is ultimately what powers our climate system. Past NASA missions showed the amount of solar radiation is not constant, but rather varies over time. SORCE will help us understand these variations, and the role of solar variability in climate change."

An artist's concept of SORCE. Credit: NASA

"Everything about climate, from droughts and ozone loss to human health problems like eye cataracts and skin cancer revolve around our understanding of the Sun," added Tom Sparn, the SORCE project manager.

Scientists say long-term records of the Sun's energy input is needed to paint a clear picture of how the planet's climate is changing.

"This is one of the climate system variables that we measure," said Gary Rottman, the SORCE principal investigator. "And by measure I don't mean for five years, I mean for the indeterminate future. We're building a long-term climate data set that I really hope that generations from now, people refer back to the measurements we make. What is the output of the Sun today to what their future measurements are."

"We need to integrate our long-term solar data with supercomputers that model Earth's climate system to see what is occurring in the big picture," Sparn added.

Such measurements have been collected over the years by previous satellites, but SORCE officials say their satellite will provide data that is more precise.

"We've been monitoring solar irradiance from space since the 1970s. So we've made improvements in the accuracy. But SORCE is really going to make the giant step forward. We're looking for improvements of at least a factor of 10," said Bill Ochs, NASA's SORCE project manager.

The SORCE spacecraft. Photo: Orbital Sciences

The five science instruments aboard SORCE are scheduled to be turned on in the coming days. In about three weeks, the instruments will start initial science data collection, measuring incoming X-ray, ultraviolet, visible, near-infrared and total solar radiation.

The SORCE project is managed by NASA's Goddard Space Flight Center, while the spacecraft's mission will be run by the University of Colorado's Laboratory for Atmospheric and Space Physics in Boulder. The university also designed, built, calibrated and tested the SORCE instruments.

Saturday's launch was the first of four Pegasus missions stacked up on the calendar through late-May.

The next flight is currently targeted for April 4 when NASA's Galaxy Evolution Explorer will be launched in a mission also originating from Cape Canaveral. But NASA Launch Manager Omar Baez says Saturday's on-time flight could allow the GALEX mission to be moved up.

"Now that we've got this mission off we'll probably accelerate the next Pegasus mission, the GALEX mission, to late March."

A launch of the long-delayed OrbView 3 commercial Earth imaging satellite for OrbImage is planned for late-April from California's Vandenberg Air Force Base.

The quartet of launches is scheduled to conclude with the Canadian SciSat 1 ozone monitoring satellite mission off the California coast around May 20.

Vandenberg is the home base for Pegasus, the site where technicians process the rockets for launch.

Video coverage for subscribers only:
   VIDEO: WATCH ENTIRE 11-MINUTE LAUNCH OF PEGASUS QT or RV
   VIDEO: TAXI OF ORBITAL CARRIER AIRCRAFT TO RUNWAY QT or RV
   VIDEO: L-1011 CARRIER JET TAKES OFF FROM CAPE QT or RV
   VIDEO: T-38 DEPARTS THE KENNEDY SPACE CENTER QT or RV
   VIDEO: AERIAL INSPECTION BY T-38 CHASE PLANE QT or RV
   VIDEO: POST-LAUNCH COMMENTS BY NASA MANAGER QT or RV
   VIDEO: PRE-LAUNCH NEWS CONFERENCE QT or RV
   VIDEO: AN OVERVIEW OF THE SORCE PROJECT QT or RV
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