More detailed explanations can be found at

​http://www.romsaf.org/general-documents/rsr/rsr_28.pdf

and

​http://www.romsaf.org/general-documents/rsr/rsr_31.pdf (eventually).

CASE_ref1d.png

Changes to the 4 standard cases, of varying degrees of difficulty, are shown here:

Generally, the bending angle profiles penetrate much deeper in ROPP9.1. This is a result of the change to the smoothing window. And in case 12 ('challenging': max |refrac gradient| above 100m between 0.1 and 0.157 N-units/m), ROPP9.1 reproduces the extremely large (0.07 rad) bending angles seen in forward modelling and high res wave optics propagators. This is a result of the inclusion of the extra term in the Fourier integral giving the signal at the LEO. Finally, without the change to the FSI code, ROPP-9.1 cannot generate a bending angle at all on case 7 ('intermediate': max |refrac gradient| above 100m between 0.079 and 0.1 N-units/m).

CASE_12_ref1d_nsample.png

There is another component of the ROPP9.1 changes: the reduction in the default number of points per 'mini-screen' from 100 to 32. Obviously this means that there are about three times as many mini-screens as before, so the propagation of the signal from the final screen to the LEO takes about three times longer, but the change is essential to capture the improvement in case 12 above. This is shown here:

Top left: (ROPP9.0_nsample=100, ROPP9.1_nsample=100); top right: (ROPP9.0_nsample=100, ROPP9.1_nsample=32);

bottom left: (ROPP9.0_nsample=32, ROPP9.1_nsample=100); bottom right: (ROPP9.0_nsample=32, ROPP9.1_nsample=32)

Comparing rows, we see that reducing nsample in ROPP9.0 smooths the bending angles but does not really increase the maximum value. On the other hand, comparing columns, we see that reducing nsample to 32 in ROPP9.1 increases the low level noise on the bending angles, but does allow the maximum value of 0.07 rad to appear.

These changes have been committed to the ic_wopt development branch at r5513, r5514 and r5515.

These have been merged into the ROPP91 prototype branch at r5626.

Sean is happy with these results, so close ticket.