How to process raw images in Photoshop Elements: steps 15-16
15 Convert the bit depth
Before you can use the Spot Healing Brush tool to remove the sensor spots, you'll need to convert the image from 16-bit to an editable 8-bit version. Choose Image>Mode and choose 8 Bits/Channel. Use the Zoom tool to examine the shot at 100%.
16 Bust the dust
Select the Spot Healing Brush tool. Choose a small soft brush tip from the Brush preset picker, and set the Type option to Proximity Match, then click each sensor spot in the sky in turn. The tool will sample a clear patch of adjacent sky and place it over each spot to hide it.