WASHINGTON, Feb. 11 -- Private U.S. firm SpaceX on Wednesday launched a satellite to monitor solar activity in what marked its first deep space mission, with its rocket softly landing on the Atlantic Ocean rather than on a floating ocean platform due to rough seas.

The satellite for the U.S. National Oceanic and Atmospheric Administration (NOAA), known as Deep Space Climate Observatory (DSCOVR), blasted off atop a SpaceX Falcon 9 rocket at 6:03 p.m. EDT (2303 GMT) from Cape Canaveral Air Force Station, Florida.

"Spacecraft head towards the sun! All good there," SpaceX CEO Elon Musk tweeted after launch.

The California-based company originally planned to land the rocket's first stage on a floating ocean platform, but said early Wednesday that such a recovery is impossible due to extreme weather at the landing site.

"We are experiencing just such weather in the Atlantic with waves reaching up to three stories in height crashing over the decks. Also, only three of the drone ship's four engines are functioning, making station-keeping in the face of such wave action extremely difficult," SpaceX said in a prelaunch statement.

Instead, SpaceX chose to land the rocket softly in the ocean, and Musk described the chance of survival as less than 1 percent shortly before the liftoff.

But the outcome appears to be a surprise. "Rocket soft landed in the ocean within 10m of target & nicely vertical!" the billionaire technology entrepreneur later wrote. "High probability of good droneship landing in non-stormy weather."

This would have been the company's second attempt to test so-called "precision landing." Its first attempt on Jan. 10 ended with the first stage landing hard on the platform, which is about 91 meters long and 52 meters wide.

The primary mission of the rocket is to send the DSCOVR, a 340-million-U.S. dollar partnership between the NOAA, the U.S. space agency NASA and the U.S. Air Force, to a place about a million miles (1.6 million km) away from Earth where the gravity of Earth and the Sun is balanced.

From that location, also known as Lagrangian point 1, the spacecraft will succeed NASA's 17-year-old Advanced Composition Explorer (ACE) to observe the solar wind that can affect power grids, communications systems and satellites close to Earth.

The U.S. agencies said this satellite location is the only place to provide 15-to-60 minute warning time before a potentially dangerous solar storm could hit Earth.

The DSCOVR, formerly known as Triana, was originally conceived in the late 1990s by then Vice President Al Gore as a NASA Earth science mission that would primarily provide a near continuous view of Earth and measure how much sunlight is reflected and emitted from our planet.

The Triana program was suspended and the satellite was put in storage in 2001 by the George W. Bush administration. Seven years later, the U.S. government re-examined the satellite and determined that it was the optimal solution for meeting NOAA space weather requirements.

NASA then renamed the satellite DSCOVR and repurposed it as a solar observatory to replace the aging ACE spacecraft, which will go into a backup status for the NOAA after the replacement.

"It was inspiring to witness the launch of the Deep Space Climate Observatory," Gore tweeted Wednesday. "Grateful to all the team members...who made #DSCOVR's mission possible."