How to Find the Descending Side of a Polar Orbit (for Remote Sensing)

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QuestionHow do you find the descending side of a polar orbit for a remote sensing satellite?
Answer

Most remote sensing satellites inhabit a polar orbit, and it is the descending side of this orbit that is the most important to an operator because the descending side is the interval when the ground is in sunlight and imaging is possible. The scenario described in this article provides an example of an efficient way to visualize and report on the start times of each descending pass of a satellite in a polar orbit.

You will need Analysis Workbench to create the intervals

1. Create a new Scalar Condition. Change the type to Data Element and Name to Descending. Create a new Condition. Set the Type to Scalar Bounds and the Name to DescendingBounds. Set the Scalar to the one you created ("Descending"). Change the Operation to Between Minimum and Maximum. Set the minimum to be -90 and the maximum to be 90 degrees.
2. Create a new Scalar Condition. Change the type to Data Element and Name to Latitude. Create a new Condition. Set the Type to Scalar Bounds to the one you created ("Latitude"). Change the operation to Between Minimum and Maximum. Set the minimum to be -80 and the maximum to be 80 degrees.
3. Create a new Interval List. Change the Type to Filtered and Name to 80_descending.  It takes 'Descending' and filters out the '80to80' times so that both must be Satisfied.  

After completing these instructions, you will have a list of all of the image window times in the 80_descending Interval List.

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