Ryuko calls out to Senketsu, who sends down the scissor blades from orbit. Ryuko lost the scissor blades in the final battle with Ragyo. So, how far up were Ryuko and Ragyo?
R = (h/2) + c^2/(8h)
= (27/2) + 873^2/(8 X 27)
= 3541.875 X 2
= 7083.75 pixels
The radius of the Earth is 6371km, and it's diameter is 12742km.
= 2*atan(7083.75/(717/tan(70/2)))
= 2.72067399 rad
= 155.88313705840463 degrees
Enter those values through the trusty angscaler, and the Earth is 1361km away. Now for our timeframe from which the scissor blades fly down from orbit to when they reach the Earth.
T = 1s/24
= 41.6666667ms X 13
= 0.541666667s + 6s
= 6.54166667s
Finally, for our speed.
T = 1361km/6.54166667s
= 208050.955/340.29
= Mach 611.393091
Final Results
Senketsu sends down the scissor blades from space = Mach 611.393