Because satellites are much closer than most celestial objects astronomers observe, they will be seen in different parts of the sky from difference vantage points on the surface of the Earth. To predict where a satellite will be observed in your night sky, your observing location on the Earth must be known.
The observing location of the GlobalStar M047 satellite at time t0 was Brockville, Ontario Canada at the following coordinates:
= -75o.6883 (West is Negative)
The Longitude and Latitude of a location on the Earth are in a convention called "Earth Center Fixed" (ECF). This indicates that no matter where you are on the Earth as it rotates, your longitude and latitude coordinates remain fixed. This is very convenient for locating objects on the Earth, but not convenient for locating objects in space. In order to perform the coordinate translation, we must transform the observer's longitude and latitude to the "Earth Center Inertial" (ECI); the convention used by the Equatorial Coordinate System.
Fortunately, the ECI Latitude of a location on the Earth is nearly the same as its ECF Latitude. In other words, the observer's Latitude on the Earth is nearly the same as the Declination of the same location as viewed from the center of the Earth. For this example, we will treat them as equal:
di = l
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Step 11: Choosing a Location Was Last Modified On April 01, 2014