StarWatch: Moravian College Astronomy

StarWatch for the greater Lehigh Valley

JULY 2009

JULY STAR MAP | STARWATCH INDEX | MOON PHASE CALENDAR

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672 JULY 5, 2009: Apollo 11: Landing on the Moon: Getting to the moon (last week’s StarWatch) was not as difficult as landing the Lunar Module (LM) named Eagle onto its surface. The command, service, and lunar module package (CSM-LM) went through two braking maneuvers which would eventually place the CSM into a circular orbit by the time the LM rendezvoused with the CSM after the landing. Some 20 hours later, and after an extensive check-out of the LM systems, which included the deployment of the Eagle’s spider-like landing gear, undocking took place. Michael Collins, who stayed in the CSM during the landing phase of the mission, visually inspected the LM as it moved away. One half orbit later, on the lunar far side, the descent engine fired, bringing the LM to an altitude of 53,000 feet above the lunar surface and within 30 minutes of touchdown. Some 260 nautical miles downrange from the landing site, power descent began, lowering Armstrong and Aldrin to an altitude of 7000 feet above the moon’s surface. At this point Eagle was rotated into an upright, windows-forward position, giving Armstrong a good view of the landing area ahead. At 1500 feet, Armstrong realized that the LM was headed for a 100 yard-in-diameter, steep-walled crater with boulders surrounding it that were the size of Volkswagens, too rough for a landing. Armstrong manually took over Eagle’s descent at 500 feet moving the spacecraft beyond the debris rich West Crater, past a smaller crater, and into a smoother patch of terrain. Below 100 feet, dust blown up by Eagle’s descent engine partially obscured visibility, but Armstrong pressed on to bring the Eagle to a touchdown that was so gentle that the astronauts were unsure that Eagle had even come to a rest. “Houston, Tranquility Base here,” Armstrong stated; “the Eagle has landed.” The time was 4:17-39 p.m. EDT on July 20, 1969.

673 JULY 12 2009: Apollo 11: Preparing to Walk: Getting to and landing on the moon were the subjects of the last two StarWatch articles. They can be found online at the URL below. Walking on the moon 40 years ago was the triumph of our national willpower to achieve the impossible, Kennedy’s 1961 challenge “of landing a man on the moon and returning him safely to the Earth.” Ironically, Neil Armstrong was unmoved by NASA’s decision that he should be the first to walk. He had a job to do—land the lunar module, Eagle—and that was all consuming. Armstrong’s pilot, Buzz Aldrin, argued that landing was the most dangerous part of the mission, and that he should walk first. NASA disagreed, sighting the 235 cubic feet of livable space inside the Eagle. Armstrong had to egress before there was sufficient room for Buzz to clear the hatch. They simply could not switch places. After landing, Neil and Buzz went through a full dress rehearsal to make sure that the Eagle could take off. Then plans called for a meal followed by a four-hour rest period. The sleep never occurred. As Buzz Aldrin recalled, “…we opted to skip the four-hour rest period. We were too excited to sleep anyway.” Aldrin also took Holy Communion, reading from the Book of John, “I am the vine, you are the branches…” It was now time to walk. The procedures for walking which included suiting up, took four and a half hours, an hour longer than expected. Depressurizing the Eagle also went at a slower rate because the air was filtered to cleanse it prior to its release. Still, when Neil Armstrong was able to pull open the hatch, the walk was running five hours ahead of schedule. The technique for getting out of the LM required a full suited Armstrong to crawl backwards onto a small platform called the porch, then down a narrow ladder to the moon’s surface. More in next week’s StarWatch...

674 JULY 19, 2009: One Small Step: Monday marks the 40th anniversary of humankind’s first step onto another world. Although we celebrate that historical week when we departed Earth to walk on the moon, the significance was not the first step, but in the technological advancements which allowed us to travel to the moon, land, walk, and return safely to the Earth. Still, as I write this article, I am infatuated by that moment when the collective spirit of humanity moved with Neil Armstrong as he stepped off the lunar module, Eagle. Even the unflappable Armstrong, who didn’t care whether he would be the first to walk, became so excited that he flubbed his now famous line, “That’s one small step for [a] man, one giant leap for mankind.” He forgot the “a.” In order to egress from the Eagle, Armstrong had to wriggle himself backwards through the hatch and onto the porch. The hatch had been recently redesigned—made smaller—and it was a challenge to pass through it. Hanging off the porch, Armstrong nearly forgot to pull the ring which activated the Modularized Equipment Stowage Assembly. It contained the video camera that would record his historic descent and the first step. Then feeling with his booted leg for the top of the ladder’s nine rungs, Armstrong cautiously backed downwards. At the last rung there was a three-foot jump to the Eagle’s footpad. Once on the pad, Armstrong pulled himself up onto the ladder’s first rung, commenting, “It takes a pretty good little jump.” Armstrong dropped for the second time onto the footpad. He described the surface as “very fine grained as you get close to it. It’s almost like a powder…” Then he continued with, “I’m going to step off the LM now.” Neil, his right hand firmly clutching the aluminum strut of the ladder, swung his booted left leg off the Eagle’s footpad and into the history books for all mankind.

675 JULY 26, 2009: Invasion of the Noctilucent Clouds: I have never seen them, but my curiosity has been piqued by recent reports of noctilucent clouds which have been seen as far south as Colorado and Nevada. These “night luminous” apparitions appear as wisps or tendrils of loosely woven electric blue light stretching across the northwestern sky, 45 to 100 minutes after sundown. The high altitude of these clouds allows them to continue to catch the light of the sun well beyond the brilliant twilight glow of a normal sunset. They are relegated to the summer months and are frequently seen above 50 degrees north latitude, but they have been creeping southward in recent weeks. Icy noctilucent clouds are formed at elevations between 47 and 53 miles in the ultra cold temperatures of the mesosphere of Earth’s ocean of air, the third of a four-tiered structure which is related to temperature. We live in the seven mile deep troposphere where virtually all weather occurs and which cools with altitude as pressures are reduced and the air expands. Temperatures go up in the stratosphere, the second layer, even though the air is still expanding. Absorption of ultraviolet radiation by ozone accounts for this increase in kinetic energy. The mesosphere cools with increasing altitude, but it is much more tenuous than the two layers below it. Finally, the ultra thin thermosphere or ionosphere warms because of the absorption of higher energy UV radiation from the sun. Current observation shows a relationship between the frequency of noctilucent clouds and solar activity. Counterintuitively, when there are fewer sunspots, Sol is actually fainter, producing less ice-destroying UV radiation which allows more mesospheric ice crystals to form and noctilucent clouds to spread southward. The current solar minimum is the deepest in nearly 100 years.

[July Star Map]

[July Moon Phase Calendar]