Update 9/18 at 8:15 p.m. EDT: The National Hurricane Center has declared Hurricane Maria a "potentially catastrophic category 5 hurricane." This article has been updated to show that the storm has been upgraded from a category 4 to category 5 hurricane. 

The Arecibo Observatory in Puerto Rico will cease observations today (Sept. 18) through Thursday (Sept. 21) and keep its visitor center closed through Sept. 28, due to the impending arrival of Hurricane Maria, officials said today on Twitter.

The facility is home to the second-largest radio telescope in the world, with a primary dish measuring 1,000 feet wide (305 meters) and 167 feet deep (50.9 meters), set into a slight depression in a mountain range. The telescope is used to study a wide variety of cosmic phenomena, look for near-Earth asteroids that could potentially collide with the planet and search for signs of alien civilizations. 

This image of Hurricane Maria was taken by NOAA's GOES East satellite on Sept. 18 at 10:45 a.m. EDT (1445 GMT) as it strengthened to a Category 3 hurricane just east of the Leeward Islands. Puerto Rico, home to the Arecibo Observatory, is just to the upper left of the storm.
This image of Hurricane Maria was taken by NOAA's GOES East satellite on Sept. 18 at 10:45 a.m. EDT (1445 GMT) as it strengthened to a Category 3 hurricane just east of the Leeward Islands. Puerto Rico, home to the Arecibo Observatory, is just to the upper left of the storm.
Credit: NASA/NOAA GOES Project

High winds from the storm are expected to reach Puerto Rico early Tuesday (Sept. 19), with the storm likely making landfall about 8 p.m. EDT (midnight GMT on Sept. 20). Earth-observing satellites from NASA and the National Oceanic and Atmospheric Administration (NOAA) have been tracking the storm's path through the Atlantic. 

"Due to the threat of Hurricane Maria, The Arecibo Observatory has begun hurricane readiness procedures," officials said on Twitter. "The preparations will include securing the telescope, physical facilities and research equipment."

Officials also said they were delaying planned social media posts in celebration of National Hispanic Heritage Month. 

This graphic shows areas affected by Hurricane Maria, and the expected dates and times when the storm will arrive at those locations.
This graphic shows areas affected by Hurricane Maria, and the expected dates and times when the storm will arrive at those locations.
Credit: NOAA

Hurricane Maria is barreling down on many Caribbean islands that were devastated by Hurricane Irma, which swept through the region earlier this month. The Arecibo Observatory also closed during Hurricane Irma, although officials reported no significant damage from the storm. 

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