Author Topic: Existing software for Impulse Response Function determination  (Read 501 times)

June 08, 2018, 08:38:17 AM

ddequal

  • Newbie
  • *
  • Posts: 3
    • View Profile
Hi everybody from Matera,

I'm trying to make some analysis of the returns from Lageos ans Starlette satellites, and I'd like to perform a simulation of the retroreflected pulses from CCR array. So far I've used the John Degnan paper "Millimeter accuracy satellite laser ranging: a review". In particular, I used 6.1.4 and 6.1.8a for the cross section of each CCR and 6.5.1 for the time delay. The results don't match the data of figure 5.5-1 of "Prelaunch  Optical characterization of the Laser Geodynamic Satellite", where a different model is used (see appendix A). Unfortunately I couldn't find any other documentation of the RETRO program used for the prelaunch analysis.

I'd like to know if any of you have worked on IRF and has some advices on how to properly reproduce them, maybe including interference and far field diffraction patterns.

Cheers

Daniele

June 18, 2018, 12:03:11 PMReply #1

jose_sgf

  • Newbie
  • *
  • Posts: 6
    • View Profile
Re: Existing software for Impulse Response Function determination
« Reply #1 on: June 18, 2018, 12:03:11 PM »
In what way your results don't match those of fig. 5.5.1? The models given in Degnan's paper are based on empirical approximations, if I remember correctly, so I wouldn't expect the intensities to be spot on. But the geometry (delay) should be fine. Did you get this bit right for the orientation shown in the figure, i.e. a laser incident on the north pole of the satellite?

June 19, 2018, 03:21:36 PMReply #2

ddequal

  • Newbie
  • *
  • Posts: 3
    • View Profile
Re: Existing software for Impulse Response Function determination
« Reply #2 on: June 19, 2018, 03:21:36 PM »
Dear Jose,

thanks for the reply, actualy both intensity and delay don't match, see the attached figure. The delay between the first and third peak is 95 ps, while in the paper is clearly more than 100. The intensities however are much more in disageement. One thing that surprises me in the ficure 5.5.1 is the ratio between the first and the third peak, which I'd expect to remain constant also when varying the pulse duration. On the contrary, I see that for 10 ps they are almost equal, for 30 ps the first peak si much smaller than the third, for 60 ps they are again similar and for 130 ps the first is again smaller. 

Cheers

Daniele

June 29, 2018, 05:04:18 PMReply #3

jose_sgf

  • Newbie
  • *
  • Posts: 6
    • View Profile
Re: Existing software for Impulse Response Function determination
« Reply #3 on: June 29, 2018, 05:04:18 PM »
Sorry for the late reply.

You are right, the intensities in the LAGEOS-2 report figure are funny. In any case, I wouldn't sweat it trying to match that data. As for the geometry, I get about 111 ps from the retro in the north pole and the third ring. It may be worth checking the expressions for the delay provided in the reports by D. Arnold, just in case what you are using is somehow different...

July 24, 2018, 02:40:22 PMReply #4

ddequal

  • Newbie
  • *
  • Posts: 3
    • View Profile
Re: Existing software for Impulse Response Function determination
« Reply #4 on: July 24, 2018, 02:40:22 PM »
Dear Jose,

I didn't check the forum for a while, however I made a comparison between the formula I found on some Arnold's papers and the one I was using, here are the results:

Peak           Arnold     my simulation
distance
1-2            28.9680   24.9776
1-3          110.7177   95.8031
1-4          243.2109  211.6056
1-5          423.1052  370.6967

the new value seems to reproduce correctly the data from RETRO. Now I'll try to see what can I do on the peak intensities.

Thanks again

Daniele