Create a new layer by going to Layer>Duplicate Layer. Rename the new layer to whatever makes the most sense to you.
Next go to Filter>Other>High Pass. Set the radius to somewhere between .05 to 3.0. The higher the radius the sharper the image.
Now go to Image>Adjustments>Hue/Saturation. Turn the saturation all the way down. Set blending mode to Overlay.
Enjoy your newly sharpened image.
Disclaimer: Because the quality of the original image was high to begin with, the changes are very slight and may be hard to notice. Use sparingly.