Published: 2015-09-25 05:00:00
Updated: 2015-09-27 21:40:10
Posted September 25, 2015
Updated September 27, 2015
By Tony Rice
There will be a rare supermoon total lunar eclipse on Sunday evening. The moon will enter the most visible part of Earth’s shadow (the umbra) at 9:07 p.m. Totality will last from 10:11 p.m. through 11:23 p.m., and the moon will exit from the shadow by 12:27 a.m.
Unfortunately this weekend's forecast isn’t promising for us to be able to see it. The southeast will be socked in by cloudy conditions into early next week.
While Sunday’s lunar eclipse is the last that will be visible from North America until January 2018, supermoon lunar eclipses are even rarer. The last we saw a lunar eclipse at perigee (the moon’s closest point in the moon's orbit to Earth, making it appear up to 14 percent larger to us) was back in 1982. We won't see this again until 2033.
The Morehead Planetarium plans an observing session at the sundial in front of the planetarium in Chapel Hill beginning at 9 p.m. Sunday. A special "eclipse edition" of the planetarium show will be presented at 8 p.m. The Raleigh Astronomy Club also plans a skywatching session at 9 p.m. at North Cary Park. Changes due to weather are a definite possibility, so check before you go.
If the forecast holds true, we can still experience this rare eclipse online. Scientists at NASA’s Marshall Spaceflight Center in Alabama will host a live web stream beginning at 8 p.m. Sunday night. In addition to views from Huntsville, Ala., (which is expecting similarly cloudy conditions), there will be views from the Adler Planetarium in Chicago and Griffith Observatory in Los Angeles which are expecting better weather.
Eclipses are beautiful and interesting events for skywatchers, but they can present some challenges for the scientists and engineers operating spacecraft studying our solar system.
The flight operations team at NASA’s Goddard Spaceflight Center in Maryland have been preparing for this eclipse for months to ensure the Lunar Reconnaissance Orbiter (LRO) makes it safely through its fourth eclipse. Now in its sixth year, LRO was originally designed for a two-year mission.
As the Earth passes between the moon and sun, the surface of the moon and any spacecraft orbiting it are plunged into darkness with only a bit of light refracted through Earth’s atmosphere making it to the moon. It takes LRO about two hours to complete a trip around the moon. That means that the spacecraft spends about an hour in sunlight and about an hour behind the moon in darkness. A total lunar eclipse increases that period of darkness and amount of time the spacecraft must operate on battery power by more than an hour.
Starting Sunday afternoon, mission controllers will be on console continuously to monitor the one-by-one shutdown of instruments putting LRO into hibernation during the eclipse. This will conserve power and help onboard heaters stay operational during the prolonged period of lower temperatures as the moon passes through Earth's shadow.
Not all instruments will be powered down Sunday however. Based on experience with the last three eclipses, the team will not power down Diviner, a radiometer which measures the temperature of the moon’s surface along with reflective energy. That instrument along with a star tracker to improve navigation will be left on to study how particles on the moon’s surface cool during this unique time.
Tony Rice is a volunteer in the NASA/JPL Solar System Ambassador program and software engineer at Cisco Systems. You can follow him on twitter @rtphokie.