Tehachapi sky watch
Atlantis held up by UFO
By: Dale Hawkins
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Posted by editor Tue Sep 26, 2006 15:48:23 PDT
Viewed 839 times
1 response 0 comments Manned Space Watch
Space Shuttle Atlantis was stopped and boarded by a Klingon Privateer that refused to identify herself, delaying Atlantis' return to earth. The Klingons made off with a case of Scotch and the commander's Mission: Impossible decoder ring. The rest of the ship was considered too primitive to be of value on the interstellar market. After a daring maneuver, Atlantis escaped destruction and landed safely... (Well, if it's in the newspaper, it must be true, right? The little boy in me still loves a good space pirate yarn.)
Actually, Atlantis was “held up” for an extra day due to concerns about the discovery of several “unidentified flying objects” floating in formation with the ship. The objects will probably never be definitively identified, but are believed to be pieces of debris from the work done on the space station during her visit. The primary concern was to ensure that none of the debris, especially a certain black object, was a heat shield tile from Atlantis. After a second look at her hull with the robotic arm, she was cleared for landing and touched down at Kennedy Space Center Thursday morning, just before dawn.
The next shuttle flight is scheduled for December when Discovery will deliver another truss segment and the SpaceHab module to Space Station Alpha. Meanwhile, a Russian Soyuz spacecraft will soon launch two new crewmembers to the station.
Night Sky Watch
The moon dominates the evening sky, setting later and growing brighter all week. If we can keep the smoke out of our sky, we should have excellent viewing after the moon sets. Don't forget your jacket!
Jupiter is still bright in the southwestern sky this week.
Saturn is getting easier to find in the eastern sky before dawn and gets higher in the sky as we head into October.
Aircraft Watch - Contrails
Have you ever wondered what the white cloudy streaks behind high-flying aircraft are, and why we see them only sometimes? This is a question I hear often.
Those beautiful streaks are called “condensation trails,” or “contrails” for short. They seem to look like they're made of the same stuff as clouds - because they are! Clouds and contrails are made of droplets of water. To understand contrails, you need to understand how clouds form.
A mass of air can hold a certain amount of water vapor that remains invisible. The amount it can hold depends on its temperature. Warm air can hold more water vapor than cold air. If the temperature of an air mass drops to the point that it can no longer hold all of its water (the “saturation point” or “dew point”), the water will try to condense into a visible cloud. The air mass temperature can decrease because the sun is no longer warming it, forming “night and morning low clouds and fog,” as is often heard in cool-season forecasts along the coast. The air mass temperature can also decrease if the air rises, since the temperature drops as you go higher in the atmosphere. This kind of cooling leads to the puffy “cumulus” clouds that “accumulate” on a warm afternoon.
However, more than a decrease in temperature to the dew point is needed to make the water condense; you also need a surface for the water to condense on. If it condenses on a car or blade of grass, we call it dew. Clouds condense on tiny particles called “condensation nuclei.” In the lower atmosphere there are plenty of dust, pollen, and pollution particles to condense on.
The upper atmosphere is much cleaner with little or no condensation nuclei for water to condense on. This can lead to a situation in which the air is colder that its dew point, meaning that the air mass is holding more water than it should be able to. It is then said to be “supersaturated.” In this case, any particle that comes along is instantly going to get wet.
The exhaust of high-flying aircraft makes for great condensation nuclei. As soon as the exhaust particles cool, water starts collecting on them and forms a continuous cloud behind the aircraft. Contrails are good evidence that there is considerable moisture in the upper atmosphere and depending on how it's moving and interrelating with other air masses, may signal unsettled weather on the horizon.
Do you have a question about aerospace? Is there a subject you'd like to have me write about? Is there an aerospace event you want me to tell Tehachapi about? Drop me a line at “hawk@ieee.org.” I'd love to hear from you.
Keep you eyes on the sky!
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