This month's AE presenter: James Aubuchon
Date of presentation: 25-Mar-2019
Subject: How to Build a Space System I, Dealing with the Earth’s Atmosphere
Description: A space system must ascend (and possibly descend) through the atmosphere. We must communicate with that system through the atmosphere. Some very small portion of the atmosphere remains even at the altitude of man-made satellites. The atmosphere has layers determined not by arbitrary boundaries, but by physical characteristics. Still, there is more than one layering system.
The best known (Troposphere, Stratosphere, Mesosphere, Thermosphere, Exosphere) is determined by temperature gradient (not temperature). For example, temperature decreases with altitude in the troposphere and increases with altitude in the stratosphere.
The atmosphere is also layered by chemical composition. The atmosphere can be divided into the lower homosphere in which the atmosphere is well stirred and the higher heterosphere where chemical layering is more pronounced. There is also an ozone layer, and an ionosphere (which, itself, has layers).
There is a lower acoustic zone and a higher anacoustic zone in which sound will not propagate. These classifications schemes overlap one another.
The physical characteristics of the various layers were discussed. The exosphere blends smoothly into outer space where the gravity of the Earth is no longer strong enough to prevent the solar radiation from removing particles from the Earth’s atmosphere.
