A telescope is orbiting the earth at 705 km altitude. The telescope lens diameter is 40 cm, the focal length is 120 cm, and the square focal plane is 20.916 cm on a side.The solar power density at the surface of the earth is 1.37 kW/m2. Ignore losses in the atmosphere.

1. Calculate the power density at the lens if the earth albedo is 50%. Calculate this power density per unit area in the scene , i.e. assume that we collect the reflected power from a 1m x 1m area in the scene.

2. Calculate the total energy intercepted from a 30m x 30m ground pixel if the shutter stays open for 0.1 millisecond.(Hint: Energy is power x integration time)

3. Calculate the field-of-view and the swath width of the telescope.

4. If the instrument is a push broom imager, calculate the number of detectors required to acquire a square image with 30m x 30m pixels on the ground. The satellite velocity of the footprint is 6760 m/sec. Calculate the dwell time if we use a scanning mirror to stare at the same area

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