MLDesign Technologies, Inc.

Mainnavigation

Subnavigation

BORDER

 
 
 

Pagecontent

Space-based Radar Analysis

The se plots and map come from an analysis of a space-based radar system. The script for this analysis is shown below.

Figure 1: Spaced based radar analysis plots
Figure 2: Spaced based radar map
  1. % Space Based Radar
  2. %
  3. % A space based radar in LEO orbit around the earth is aquiring
  4. % targets and observing them over a specified observation angle.
  5. % After observing the one target the SBR is aquiring and observing
  6. % another target. The slew angles of the satellite, the integrated
  7. % observation angle and the angle from the targets to the SBR are
  8. % computed and displayed
  9.  
  10. clear;
  11. clearGraphic;
  12. removeAll;
  13.  
  14. % loadreplaceAll("./SBR.data")
  15.  
  16. % Start of simulation
  17. setSimEpoch(2000,3,21,19,55,0);
  18. addEpoch('equinox',2000,3,21,12,0,0)
  19. addEpoch('Start',2000,3,21,12,0,0)
  20. addSatellite('SBR',6953.137,.03,63.435,0,45,0,'equinox');
  21. addStation('Denver',I_earth,0,39.75,-104.99,1.61);
  22. addStation('Little Rock',I_earth,0,34.74,-92.28,.087);
  23. addStation('Chicago',I_earth,0,41.87,-87.64,.181);
  24.  
  25. %Limits:
  26. %
  27. % Constraint on satellite: 45 < AZ < 135 || -45 > AZ > -135 deg
  28. SAZmin1 = 45*d2r;
  29. SAZmax1 = 135*d2r;
  30. SAZmin2 =-135*d2r;
  31. SAZmax2 = -45*d2r;
  32.  
  33. % Constraint on target: 20 <= EL <= 70 deg
  34. GS_ELmin = 20*d2r;
  35. GS_ELmax = 70*d2r;
  36.  
  37. % Pickup Constraint: 45 <= AZ <= 85 || -45 >= AZ >= -85 deg
  38. PCAZmin1 = 45*d2r;
  39. PCAZmax1 = 85*d2r;
  40. PCAZmin2 = -85*d2r;
  41. PCAZmax2 = -45*d2r;
  42.  
  43. % Integration angle of observation 45 deg
  44. cos_int_ang = cos(45*d2r);
  45. nStations   = NumberOfNodes(1);
  46. nMobiles    = NumberOfNodes(2);
  47. nSatellites = NumberOfNodes(3);
  48. iSatellites = nStations+nMobiles+1;
  49. nNodes      = NumberOfNodes(4);
  50. g_earth     = GeoPosition(1)*r2d;
  51.  
  52. for i=1:nStations
  53.     latitude(i)=g_earth(1,i);
  54.     longitude(i)=g_earth(2,i);
  55. endfor
  56.  
  57. % open display
  58. %id=addMapView();
  59. id=1;
  60. setLineColor(id,"white");
  61. dt  = 3;    % simulation step in sec
  62. maxt = 800; % maximum simulation time in sec
  63.  
  64. t      = 0:dt:maxt;
  65. iStart = 0;
  66. j      = 0;
  67. jj     = 0;
  68.  
  69. setSimStepSize(dt);
  70. for t1 = t,
  71.     [d,r,a,el,v] = RelPosition();
  72.     jj = jj+1;
  73.     EE(jj) = el(3,4)*r2d;
  74.     AA(jj)=a(4,3)*r2d;
  75.     %if satellite is in target constraint start observation
  76.     if iStart < 1,
  77.         ETarget = el(1:nStations,iSatellites);
  78.         condTarget = 0;
  79.         for i = 1:nStations,
  80.             if condTarget==0,
  81.                 if ETarget(i) >= GS_ELmin && ETarget(i) <= GS_ELmax,
  82.                     eTarget = ETarget(i);
  83.                     aSat = a(iSatellites,i);
  84.                     %check pickup criteria
  85.                     if((aSat >= PCAZmin1 && aSat <= PCAZmax1) ||
  86.                          (aSat >= PCAZmin2 && aSat <= PCAZmax2)),
  87.                         condTarget = i;
  88.                     endif
  89.                 endif
  90.             endif
  91.         endfor
  92.     endif
  93.  
  94.     if condTarget > 0,
  95.         eTarget = el(condTarget,iSatellites);
  96.         aTarget = a(condTarget,iSatellites);
  97.         if eTarget >= GS_ELmin && eTarget <= GS_ELmax,
  98.             %if target is in satellite constraint
  99.             aSat = a(iSatellites,condTarget);
  100.             if((aSat >= SAZmin1 && aSat <= SAZmax1) ||
  101.                 (aSat >= SAZmin2 && aSat <= SAZmax2))
  102.                 if iStart < 1,
  103.                     iunitvector = unitvector(aTarget,eTarget);
  104.                     iStart = 1;
  105.                 endif
  106.  
  107.                 uv = unitvector(aTarget,eTarget);
  108.                 cos_sw_angle = uv`*iunitvector;
  109.                 %within observation task
  110.                 if cos_sw_angle >= cos_int_ang,
  111.                     j = j+1;
  112.                     afs(j) = aSat*r2d;
  113.                     eft(j) = eTarget*r2d;
  114.                     D(j)   = d(condTarget,iSatellites);
  115.                     V(j)   = r(condTarget,iSatellites);
  116.                     T(j)   = t1;
  117.                     OA(j)  = acos(cos_sw_angle)*r2d;
  118.                     g_Sat  = GeoPosition(N_satellite)*r2d;
  119.                     lonS   = g_Sat(2);
  120.                     latS   = g_Sat(1);
  121.                     lonT   = longitude(condTarget);
  122.                     latT   = latitude(condTarget);
  123.                     drawLine(id,lonS,latS,lonT,latT);
  124.                 else
  125.                     iStart = 0;
  126.                     condTarget=0;
  127.                 endif
  128.             endif
  129.         endif
  130.     endif
  131.  
  132.     stepSim;
  133. endfor
  134.  
  135. erase
  136. window('111')
  137. title('SBR: h=575 km, Observation Angle = 45 deg')
  138.  
  139. window('221')
  140. plot(T,afs,'grid','red,point=3')
  141. ylabel("AZ from Sat [deg]")
  142.  
  143. window('222')
  144. plot(T,eft,'grid','green,point=3')
  145. ylabel("EL from target [deg]")
  146.  
  147. window('223')
  148. plot(T,D,'grid','red,point=3')
  149. ylabel('Slant Range [km]')
  150.  
  151. window('224')
  152. plot(T,OA,'grid','red,point=3')
  153. ylabel('Observation angle [deg]')
  154. xlabel('time [sec]')
  155.