MWA 'sweet spots' and gridpoint numbers

Owned by Andrew Williams
Last updated: May 16, 2024 by Dev Null
8 min read

The need for 'sweet spots' and a grid of positions that the the telescope can point to is driven by the beamformer architecture. Each dipole can be delayed by an integer multiple of 435 picoseconds, where that integer ranges from 0-31, so the 'sweet spots' are the set of all of the positions on the sky where the geometric delays on every dipole on a tile are equal to an integer multiple of 435 picoseconds.

There's a table in the database that contains all of these positions. When we designed the system, we thought that some groups (like EOR) would only want to use a subset of all of the possible 'sweet spot' positions, so we allowed for multiple 'grids', each with a different name.

The set of every possible pointing with integer delays is called the 'sweet' grid:


  N  |    az    |   el    |                     delays
-----+----------+---------+------------------------------------------------
   0 |        0 |      90 | {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}
   1 |        0 | 83.1912 | {3,3,3,3,2,2,2,2,1,1,1,1,0,0,0,0}
   2 |       90 | 83.1912 | {0,1,2,3,0,1,2,3,0,1,2,3,0,1,2,3}
   3 |      180 | 83.1912 | {0,0,0,0,1,1,1,1,2,2,2,2,3,3,3,3}
   4 |      270 | 83.1912 | {3,2,1,0,3,2,1,0,3,2,1,0,3,2,1,0}
   5 |       45 |  80.348 | {3,4,5,6,2,3,4,5,1,2,3,4,0,1,2,3}
   6 |      135 |  80.348 | {0,1,2,3,1,2,3,4,2,3,4,5,3,4,5,6}
   7 |      225 |  80.348 | {3,2,1,0,4,3,2,1,5,4,3,2,6,5,4,3}
   8 |      315 |  80.348 | {6,5,4,3,5,4,3,2,4,3,2,1,3,2,1,0}
   9 |        0 | 76.2838 | {6,6,6,6,4,4,4,4,2,2,2,2,0,0,0,0}
  10 |       90 | 76.2838 | {0,2,4,6,0,2,4,6,0,2,4,6,0,2,4,6}
  11 |      180 | 76.2838 | {0,0,0,0,2,2,2,2,4,4,4,4,6,6,6,6}
  12 |      270 | 76.2838 | {6,4,2,0,6,4,2,0,6,4,2,0,6,4,2,0}
  13 |  26.5651 | 74.6271 | {6,7,8,9,4,5,6,7,2,3,4,5,0,1,2,3}
  14 |  63.4349 | 74.6271 | {3,5,7,9,2,4,6,8,1,3,5,7,0,2,4,6}
  15 | 116.5651 | 74.6271 | {0,2,4,6,1,3,5,7,2,4,6,8,3,5,7,9}
  16 | 153.4349 | 74.6271 | {0,1,2,3,2,3,4,5,4,5,6,7,6,7,8,9}
  17 | 206.5651 | 74.6271 | {3,2,1,0,5,4,3,2,7,6,5,4,9,8,7,6}
  18 | 243.4349 | 74.6271 | {6,4,2,0,7,5,3,1,8,6,4,2,9,7,5,3}
  19 | 296.5651 | 74.6271 | {9,7,5,3,8,6,4,2,7,5,3,1,6,4,2,0}
  20 | 333.4349 | 74.6271 | {9,8,7,6,7,6,5,4,5,4,3,2,3,2,1,0}
  21 |       45 | 70.4075 | {6,8,10,12,4,6,8,10,2,4,6,8,0,2,4,6}
  22 |      135 | 70.4075 | {0,2,4,6,2,4,6,8,4,6,8,10,6,8,10,12}
  23 |      225 | 70.4075 | {6,4,2,0,8,6,4,2,10,8,6,4,12,10,8,6}
  24 |      315 | 70.4075 | {12,10,8,6,10,8,6,4,8,6,4,2,6,4,2,0}
  25 |        0 | 69.1655 | {9,9,9,9,6,6,6,6,3,3,3,3,0,0,0,0}
  26 |       90 | 69.1655 | {0,3,6,9,0,3,6,9,0,3,6,9,0,3,6,9}
  27 |      180 | 69.1655 | {0,0,0,0,3,3,3,3,6,6,6,6,9,9,9,9}
  28 |      270 | 69.1655 | {9,6,3,0,9,6,3,0,9,6,3,0,9,6,3,0}
  29 |  18.4349 | 67.9813 | {9,10,11,12,6,7,8,9,3,4,5,6,0,1,2,3}
  30 |  71.5651 | 67.9813 | {3,6,9,12,2,5,8,11,1,4,7,10,0,3,6,9}
  31 | 108.4349 | 67.9813 | {0,3,6,9,1,4,7,10,2,5,8,11,3,6,9,12}
  32 | 161.5651 | 67.9813 | {0,1,2,3,3,4,5,6,6,7,8,9,9,10,11,12}
  33 | 198.4349 | 67.9813 | {3,2,1,0,6,5,4,3,9,8,7,6,12,11,10,9}
  34 | 251.5651 | 67.9813 | {9,6,3,0,10,7,4,1,11,8,5,2,12,9,6,3}
  35 | 288.4349 | 67.9813 | {12,9,6,3,11,8,5,2,10,7,4,1,9,6,3,0}
  36 | 341.5651 | 67.9813 | {12,11,10,9,9,8,7,6,6,5,4,3,3,2,1,0}
  37 |  33.6901 | 64.6934 | {9,11,13,15,6,8,10,12,3,5,7,9,0,2,4,6}
  38 |  56.3099 | 64.6934 | {6,9,12,15,4,7,10,13,2,5,8,11,0,3,6,9}
  39 | 123.6901 | 64.6934 | {0,3,6,9,2,5,8,11,4,7,10,13,6,9,12,15}
  40 | 146.3099 | 64.6934 | {0,2,4,6,3,5,7,9,6,8,10,12,9,11,13,15}
  41 | 213.6901 | 64.6934 | {6,4,2,0,9,7,5,3,12,10,8,6,15,13,11,9}
  42 | 236.3099 | 64.6934 | {9,6,3,0,11,8,5,2,13,10,7,4,15,12,9,6}
  43 | 303.6901 | 64.6934 | {15,12,9,6,13,10,7,4,11,8,5,2,9,6,3,0}
  44 | 326.3099 | 64.6934 | {15,13,11,9,12,10,8,6,9,7,5,3,6,4,2,0}
  45 |        0 |  61.691 | {12,12,12,12,8,8,8,8,4,4,4,4,0,0,0,0}
  46 |       90 |  61.691 | {0,4,8,12,0,4,8,12,0,4,8,12,0,4,8,12}
  47 |      180 |  61.691 | {0,0,0,0,4,4,4,4,8,8,8,8,12,12,12,12}
  48 |      270 |  61.691 | {12,8,4,0,12,8,4,0,12,8,4,0,12,8,4,0}
  49 |  14.0362 | 60.7369 | {12,13,14,15,8,9,10,11,4,5,6,7,0,1,2,3}
  50 |  75.9638 | 60.7369 | {3,7,11,15,2,6,10,14,1,5,9,13,0,4,8,12}
  51 | 104.0362 | 60.7369 | {0,4,8,12,1,5,9,13,2,6,10,14,3,7,11,15}
  52 | 165.9638 | 60.7369 | {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15}
  53 | 194.0362 | 60.7369 | {3,2,1,0,7,6,5,4,11,10,9,8,15,14,13,12}
  54 | 255.9638 | 60.7369 | {12,8,4,0,13,9,5,1,14,10,6,2,15,11,7,3}
  55 | 284.0362 | 60.7369 | {15,11,7,3,14,10,6,2,13,9,5,1,12,8,4,0}
  56 | 345.9638 | 60.7369 | {15,14,13,12,11,10,9,8,7,6,5,4,3,2,1,0}
  57 |       45 | 59.8018 | {9,12,15,18,6,9,12,15,3,6,9,12,0,3,6,9}
  58 |      135 | 59.8018 | {0,3,6,9,3,6,9,12,6,9,12,15,9,12,15,18}
  59 |      225 | 59.8018 | {9,6,3,0,12,9,6,3,15,12,9,6,18,15,12,9}
  60 |      315 | 59.8018 | {18,15,12,9,15,12,9,6,12,9,6,3,9,6,3,0}
  61 |  26.5651 |  57.981 | {12,14,16,18,8,10,12,14,4,6,8,10,0,2,4,6}
  62 |  63.4349 |  57.981 | {6,10,14,18,4,8,12,16,2,6,10,14,0,4,8,12}
  63 | 116.5651 |  57.981 | {0,4,8,12,2,6,10,14,4,8,12,16,6,10,14,18}
  64 | 153.4349 |  57.981 | {0,2,4,6,4,6,8,10,8,10,12,14,12,14,16,18}
  65 | 206.5651 |  57.981 | {6,4,2,0,10,8,6,4,14,12,10,8,18,16,14,12}
  66 | 243.4349 |  57.981 | {12,8,4,0,14,10,6,2,16,12,8,4,18,14,10,6}
  67 | 296.5651 |  57.981 | {18,14,10,6,16,12,8,4,14,10,6,2,12,8,4,0}
  68 | 333.4349 |  57.981 | {18,16,14,12,14,12,10,8,10,8,6,4,6,4,2,0}
  69 |        0 | 53.6453 | {15,15,15,15,10,10,10,10,5,5,5,5,0,0,0,0}
  70 |  36.8699 | 53.6453 | {12,15,18,21,8,11,14,17,4,7,10,13,0,3,6,9}
  71 |  53.1301 | 53.6453 | {9,13,17,21,6,10,14,18,3,7,11,15,0,4,8,12}
  72 |       90 | 53.6453 | {0,5,10,15,0,5,10,15,0,5,10,15,0,5,10,15}
  73 | 126.8699 | 53.6453 | {0,4,8,12,3,7,11,15,6,10,14,18,9,13,17,21}
  74 | 143.1301 | 53.6453 | {0,3,6,9,4,7,10,13,8,11,14,17,12,15,18,21}
  75 |      180 | 53.6453 | {0,0,0,0,5,5,5,5,10,10,10,10,15,15,15,15}
  76 | 216.8699 | 53.6453 | {9,6,3,0,13,10,7,4,17,14,11,8,21,18,15,12}
  77 | 233.1301 | 53.6453 | {12,8,4,0,15,11,7,3,18,14,10,6,21,17,13,9}
  78 |      270 | 53.6453 | {15,10,5,0,15,10,5,0,15,10,5,0,15,10,5,0}
  79 | 306.8699 | 53.6453 | {21,17,13,9,18,14,10,6,15,11,7,3,12,8,4,0}
  80 | 323.1301 | 53.6453 | {21,18,15,12,17,14,11,8,13,10,7,4,9,6,3,0}
  81 |  11.3099 | 52.8056 | {15,16,17,18,10,11,12,13,5,6,7,8,0,1,2,3}
  82 |  78.6901 | 52.8056 | {3,8,13,18,2,7,12,17,1,6,11,16,0,5,10,15}
  83 | 101.3099 | 52.8056 | {0,5,10,15,1,6,11,16,2,7,12,17,3,8,13,18}
  84 | 168.6901 | 52.8056 | {0,1,2,3,5,6,7,8,10,11,12,13,15,16,17,18}
  85 | 191.3099 | 52.8056 | {3,2,1,0,8,7,6,5,13,12,11,10,18,17,16,15}
  86 | 258.6901 | 52.8056 | {15,10,5,0,16,11,6,1,17,12,7,2,18,13,8,3}
  87 | 281.3099 | 52.8056 | {18,13,8,3,17,12,7,2,16,11,6,1,15,10,5,0}
  88 | 348.6901 | 52.8056 | {18,17,16,15,13,12,11,10,8,7,6,5,3,2,1,0}
  89 |  21.8014 | 50.3239 | {15,17,19,21,10,12,14,16,5,7,9,11,0,2,4,6}
  90 |  68.1986 | 50.3239 | {6,11,16,21,4,9,14,19,2,7,12,17,0,5,10,15}
  91 | 111.8014 | 50.3239 | {0,5,10,15,2,7,12,17,4,9,14,19,6,11,16,21}
  92 | 158.1986 | 50.3239 | {0,2,4,6,5,7,9,11,10,12,14,16,15,17,19,21}
  93 | 201.8014 | 50.3239 | {6,4,2,0,11,9,7,5,16,14,12,10,21,19,17,15}
  94 | 248.1986 | 50.3239 | {15,10,5,0,17,12,7,2,19,14,9,4,21,16,11,6}
  95 | 291.8014 | 50.3239 | {21,16,11,6,19,14,9,4,17,12,7,2,15,10,5,0}
  96 | 338.1986 | 50.3239 | {21,19,17,15,16,14,12,10,11,9,7,5,6,4,2,0}
  97 |       45 | 47.8822 | {12,16,20,24,8,12,16,20,4,8,12,16,0,4,8,12}
  98 |      135 | 47.8822 | {0,4,8,12,4,8,12,16,8,12,16,20,12,16,20,24}
  99 |      225 | 47.8822 | {12,8,4,0,16,12,8,4,20,16,12,8,24,20,16,12}
 100 |      315 | 47.8822 | {24,20,16,12,20,16,12,8,16,12,8,4,12,8,4,0}
 101 |  30.9638 | 46.2671 | {15,18,21,24,10,13,16,19,5,8,11,14,0,3,6,9}
 102 |  59.0362 | 46.2671 | {9,14,19,24,6,11,16,21,3,8,13,18,0,5,10,15}
 103 | 120.9638 | 46.2671 | {0,5,10,15,3,8,13,18,6,11,16,21,9,14,19,24}
 104 | 149.0362 | 46.2671 | {0,3,6,9,5,8,11,14,10,13,16,19,15,18,21,24}
 105 | 210.9638 | 46.2671 | {9,6,3,0,14,11,8,5,19,16,13,10,24,21,18,15}
 106 | 239.0362 | 46.2671 | {15,10,5,0,18,13,8,3,21,16,11,6,24,19,14,9}
 107 | 300.9638 | 46.2671 | {24,19,14,9,21,16,11,6,18,13,8,3,15,10,5,0}
 108 | 329.0362 | 46.2671 | {24,21,18,15,19,16,13,10,14,11,8,5,9,6,3,0}
 109 |        0 |  44.656 | {18,18,18,18,12,12,12,12,6,6,6,6,0,0,0,0}
 110 |       90 |  44.656 | {0,6,12,18,0,6,12,18,0,6,12,18,0,6,12,18}
 111 |      180 |  44.656 | {0,0,0,0,6,6,6,6,12,12,12,12,18,18,18,18}
 112 |      270 |  44.656 | {18,12,6,0,18,12,6,0,18,12,6,0,18,12,6,0}
 113 |   9.4623 | 43.8504 | {18,19,20,21,12,13,14,15,6,7,8,9,0,1,2,3}
 114 |  80.5377 | 43.8504 | {3,9,15,21,2,8,14,20,1,7,13,19,0,6,12,18}
 115 |  99.4623 | 43.8504 | {0,6,12,18,1,7,13,19,2,8,14,20,3,9,15,21}
 116 | 170.5377 | 43.8504 | {0,1,2,3,6,7,8,9,12,13,14,15,18,19,20,21}
 117 | 189.4623 | 43.8504 | {3,2,1,0,9,8,7,6,15,14,13,12,21,20,19,18}
 118 | 260.5377 | 43.8504 | {18,12,6,0,19,13,7,1,20,14,8,2,21,15,9,3}
 119 | 279.4623 | 43.8504 | {21,15,9,3,20,14,8,2,19,13,7,1,18,12,6,0}
 120 | 350.5377 | 43.8504 | {21,20,19,18,15,14,13,12,9,8,7,6,3,2,1,0}
 121 |  18.4349 | 41.4255 | {18,20,22,24,12,14,16,18,6,8,10,12,0,2,4,6}
 122 |  71.5651 | 41.4255 | {6,12,18,24,4,10,16,22,2,8,14,20,0,6,12,18}
 123 | 108.4349 | 41.4255 | {0,6,12,18,2,8,14,20,4,10,16,22,6,12,18,24}
 124 | 161.5651 | 41.4255 | {0,2,4,6,6,8,10,12,12,14,16,18,18,20,22,24}
 125 | 198.4349 | 41.4255 | {6,4,2,0,12,10,8,6,18,16,14,12,24,22,20,18}
 126 | 251.5651 | 41.4255 | {18,12,6,0,20,14,8,2,22,16,10,4,24,18,12,6}
 127 | 288.4349 | 41.4255 | {24,18,12,6,22,16,10,4,20,14,8,2,18,12,6,0}
 128 | 341.5651 | 41.4255 | {24,22,20,18,18,16,14,12,12,10,8,6,6,4,2,0}
 129 |  38.6598 | 40.6123 | {15,19,23,27,10,14,18,22,5,9,13,17,0,4,8,12}
 130 |  51.3402 | 40.6123 | {12,17,22,27,8,13,18,23,4,9,14,19,0,5,10,15}
 131 | 128.6598 | 40.6123 | {0,5,10,15,4,9,14,19,8,13,18,23,12,17,22,27}
 132 | 141.3402 | 40.6123 | {0,4,8,12,5,9,13,17,10,14,18,22,15,19,23,27}
 133 | 218.6598 | 40.6123 | {12,8,4,0,17,13,9,5,22,18,14,10,27,23,19,15}
 134 | 231.3402 | 40.6123 | {15,10,5,0,19,14,9,4,23,18,13,8,27,22,17,12}
 135 | 308.6598 | 40.6123 | {27,22,17,12,23,18,13,8,19,14,9,4,15,10,5,0}
 136 | 321.3402 | 40.6123 | {27,23,19,15,22,18,14,10,17,13,9,5,12,8,4,0}
 137 |  26.5651 | 37.3163 | {18,21,24,27,12,15,18,21,6,9,12,15,0,3,6,9}
 138 |  63.4349 | 37.3163 | {9,15,21,27,6,12,18,24,3,9,15,21,0,6,12,18}
 139 | 116.5651 | 37.3163 | {0,6,12,18,3,9,15,21,6,12,18,24,9,15,21,27}
 140 | 153.4349 | 37.3163 | {0,3,6,9,6,9,12,15,12,15,18,21,18,21,24,27}
 141 | 206.5651 | 37.3163 | {9,6,3,0,15,12,9,6,21,18,15,12,27,24,21,18}
 142 | 243.4349 | 37.3163 | {18,12,6,0,21,15,9,3,24,18,12,6,27,21,15,9}
 143 | 296.5651 | 37.3163 | {27,21,15,9,24,18,12,6,21,15,9,3,18,12,6,0}
 144 | 333.4349 | 37.3163 | {27,24,21,18,21,18,15,12,15,12,9,6,9,6,3,0}
 145 |        0 |  33.912 | {21,21,21,21,14,14,14,14,7,7,7,7,0,0,0,0}
 146 |       90 |  33.912 | {0,7,14,21,0,7,14,21,0,7,14,21,0,7,14,21}
 147 |      180 |  33.912 | {0,0,0,0,7,7,7,7,14,14,14,14,21,21,21,21}
 148 |      270 |  33.912 | {21,14,7,0,21,14,7,0,21,14,7,0,21,14,7,0}
 149 |   8.1301 | 33.0368 | {21,22,23,24,14,15,16,17,7,8,9,10,0,1,2,3}
 150 |       45 | 33.0368 | {15,20,25,30,10,15,20,25,5,10,15,20,0,5,10,15}
 151 |  81.8699 | 33.0368 | {3,10,17,24,2,9,16,23,1,8,15,22,0,7,14,21}
 152 |  98.1301 | 33.0368 | {0,7,14,21,1,8,15,22,2,9,16,23,3,10,17,24}
 153 |      135 | 33.0368 | {0,5,10,15,5,10,15,20,10,15,20,25,15,20,25,30}
 154 | 171.8699 | 33.0368 | {0,1,2,3,7,8,9,10,14,15,16,17,21,22,23,24}
 155 | 188.1301 | 33.0368 | {3,2,1,0,10,9,8,7,17,16,15,14,24,23,22,21}
 156 |      225 | 33.0368 | {15,10,5,0,20,15,10,5,25,20,15,10,30,25,20,15}
 157 | 261.8699 | 33.0368 | {21,14,7,0,22,15,8,1,23,16,9,2,24,17,10,3}
 158 | 278.1301 | 33.0368 | {24,17,10,3,23,16,9,2,22,15,8,1,21,14,7,0}
 159 |      315 | 33.0368 | {30,25,20,15,25,20,15,10,20,15,10,5,15,10,5,0}
 160 | 351.8699 | 33.0368 | {24,23,22,21,17,16,15,14,10,9,8,7,3,2,1,0}
 161 |  33.6901 | 31.2488 | {18,22,26,30,12,16,20,24,6,10,14,18,0,4,8,12}
 162 |  56.3099 | 31.2488 | {12,18,24,30,8,14,20,26,4,10,16,22,0,6,12,18}
 163 | 123.6901 | 31.2488 | {0,6,12,18,4,10,16,22,8,14,20,26,12,18,24,30}
 164 | 146.3099 | 31.2488 | {0,4,8,12,6,10,14,18,12,16,20,24,18,22,26,30}
 165 | 213.6901 | 31.2488 | {12,8,4,0,18,14,10,6,24,20,16,12,30,26,22,18}
 166 | 236.3099 | 31.2488 | {18,12,6,0,22,16,10,4,26,20,14,8,30,24,18,12}
 167 | 303.6901 | 31.2488 | {30,24,18,12,26,20,14,8,22,16,10,4,18,12,6,0}
 168 | 326.3099 | 31.2488 | {30,26,22,18,24,20,16,12,18,14,10,6,12,8,4,0}
 169 |  15.9454 | 30.3331 | {21,23,25,27,14,16,18,20,7,9,11,13,0,2,4,6}
 170 |  74.0546 | 30.3331 | {6,13,20,27,4,11,18,25,2,9,16,23,0,7,14,21}
 171 | 105.9454 | 30.3331 | {0,7,14,21,2,9,16,23,4,11,18,25,6,13,20,27}
 172 | 164.0546 | 30.3331 | {0,2,4,6,7,9,11,13,14,16,18,20,21,23,25,27}
 173 | 195.9454 | 30.3331 | {6,4,2,0,13,11,9,7,20,18,16,14,27,25,23,21}
 174 | 254.0546 | 30.3331 | {21,14,7,0,23,16,9,2,25,18,11,4,27,20,13,6}
 175 | 285.9454 | 30.3331 | {27,20,13,6,25,18,11,4,23,16,9,2,21,14,7,0}
 176 | 344.0546 | 30.3331 | {27,25,23,21,20,18,16,14,13,11,9,7,6,4,2,0}
 177 |  23.1986 | 25.4582 | {21,24,27,30,14,17,20,23,7,10,13,16,0,3,6,9}
 178 |  66.8014 | 25.4582 | {9,16,23,30,6,13,20,27,3,10,17,24,0,7,14,21}
 179 | 113.1986 | 25.4582 | {0,7,14,21,3,10,17,24,6,13,20,27,9,16,23,30}
 180 | 156.8014 | 25.4582 | {0,3,6,9,7,10,13,16,14,17,20,23,21,24,27,30}
 181 | 203.1986 | 25.4582 | {9,6,3,0,16,13,10,7,23,20,17,14,30,27,24,21}
 182 | 246.8014 | 25.4582 | {21,14,7,0,24,17,10,3,27,20,13,6,30,23,16,9}
 183 | 293.1986 | 25.4582 | {30,23,16,9,27,20,13,6,24,17,10,3,21,14,7,0}
 184 | 336.8014 | 25.4582 | {30,27,24,21,23,20,17,14,16,13,10,7,9,6,3,0}
 185 |        0 | 18.4768 | {24,24,24,24,16,16,16,16,8,8,8,8,0,0,0,0}
 186 |       90 | 18.4768 | {0,8,16,24,0,8,16,24,0,8,16,24,0,8,16,24}
 187 |      180 | 18.4768 | {0,0,0,0,8,8,8,8,16,16,16,16,24,24,24,24}
 188 |      270 | 18.4768 | {24,16,8,0,24,16,8,0,24,16,8,0,24,16,8,0}
 189 |    7.125 | 17.0922 | {24,25,26,27,16,17,18,19,8,9,10,11,0,1,2,3}
 190 |   82.875 | 17.0922 | {3,11,19,27,2,10,18,26,1,9,17,25,0,8,16,24}
 191 |   97.125 | 17.0922 | {0,8,16,24,1,9,17,25,2,10,18,26,3,11,19,27}
 192 |  172.875 | 17.0922 | {0,1,2,3,8,9,10,11,16,17,18,19,24,25,26,27}
 193 |  187.125 | 17.0922 | {3,2,1,0,11,10,9,8,19,18,17,16,27,26,25,24}
 194 |  262.875 | 17.0922 | {24,16,8,0,25,17,9,1,26,18,10,2,27,19,11,3}
 195 |  277.125 | 17.0922 | {27,19,11,3,26,18,10,2,25,17,9,1,24,16,8,0}
 196 |  352.875 | 17.0922 | {27,26,25,24,19,18,17,16,11,10,9,8,3,2,1,0}


When an observation is scheduled, it finds the closest 'sweet' grid position (by default) to the supplied RA/Dec, Az/El or source position, and uses those delays for the beamformers.

The 'EOR1' grid only has 11 positions, and was used during the observations for the first few EoR observing seasons:


 n  |    az    |   el    |                  delays
----+----------+---------+-------------------------------------------
  0 |        0 |      90 | {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}
  1 |       90 | 83.1912 | {0,1,2,3,0,1,2,3,0,1,2,3,0,1,2,3}
  2 |      270 | 83.1912 | {3,2,1,0,3,2,1,0,3,2,1,0,3,2,1,0}
  3 |       90 | 76.2838 | {0,2,4,6,0,2,4,6,0,2,4,6,0,2,4,6}
  4 |      270 | 76.2838 | {6,4,2,0,6,4,2,0,6,4,2,0,6,4,2,0}
  5 |       90 | 69.1655 | {0,3,6,9,0,3,6,9,0,3,6,9,0,3,6,9}
  6 |      270 | 69.1655 | {9,6,3,0,9,6,3,0,9,6,3,0,9,6,3,0}
  7 | 104.0362 | 60.7369 | {0,4,8,12,1,5,9,13,2,6,10,14,3,7,11,15}
  8 | 255.9638 | 60.7369 | {12,8,4,0,13,9,5,1,14,10,6,2,15,11,7,3}
  9 | 101.3099 | 52.8056 | {0,5,10,15,1,6,11,16,2,7,12,17,3,8,13,18}
 10 | 281.3099 | 52.8056 | {18,13,8,3,17,12,7,2,16,11,6,1,15,10,5,0}


You can see that EOR1 grid point 0 has the same delays (and az/el) as 'sweet' grid point 0, but EOR1 grid point 1 matches 'sweet' grid point 2, EOR grid point 2 matches 'sweet' grid point 4, etc.

The full mapping between the two is here:


EOR1  sweet      delays
0     0    [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
1     2    [0,1,2,3,0,1,2,3,0,1,2,3,0,1,2,3]
2     4    [3,2,1,0,3,2,1,0,3,2,1,0,3,2,1,0]
3    10    [0,2,4,6,0,2,4,6,0,2,4,6,0,2,4,6]
4    12    [6,4,2,0,6,4,2,0,6,4,2,0,6,4,2,0]
5    26    [0,3,6,9,0,3,6,9,0,3,6,9,0,3,6,9]
6    28    [9,6,3,0,9,6,3,0,9,6,3,0,9,6,3,0]
7    51    [0,4,8,12,1,5,9,13,2,6,10,14,3,7,11,15]
8    54    [12,8,4,0,13,9,5,1,14,10,6,2,15,11,7,3]
9    83    [0,5,10,15,1,6,11,16,2,7,12,17,3,8,13,18]
10   87    [18,13,8,3,17,12,7,2,16,11,6,1,15,10,5,0]


For the first few years of MWA observations, EOR observations were scheduled with the 'EOR1' grid point numbers, but then everyone started using 'sweet' gridpoint numbers for all observations. The only important thing is what actual delays are sent to the beamformers, not what the grid point number name is.

East-West Pointings

EoR observations typically only use the pointings directly east or west of zenith. The EoR group refers to these pointings with labels from -3 to +3.

This table shows the mapping between:

  • SW - gridpoint number when gridpoint_name="sweet"
  • E1 - gridpoint number when gridpoint_name="eor1"
  • EW - "east-west" pointings
  • az/el - azimuth and elevation (degrees)
  • lsts range of local sidereal times for observations of the eor0 field at right ascension 0 (in degrees)
| EW | E1 | SW |  az |    el |        delays |    lsts  |
|----+----+----+-----+-------+-------------- | -------- |
| -3 |  5 | 26 |  90 | 69.16 | {0,3,6,9,...} | -28..-20 |
| -2 |  3 | 10 |  90 | 76.28 | {0,2,4,6,...} | -19..-12 |
| -1 |  1 |  2 |  90 | 83.19 | {0,1,2,3,...} | -12..-4  |
|  0 |  0 |  0 |   0 | 90.00 | {0,0,0,0,...} |  -4..+4  |
| +1 |  2 |  4 | 270 | 83.19 | {3,2,1,0,...} |  +4..+12 |
| +2 |  4 | 12 | 270 | 76.28 | {6,4,2,0,...} | +11..+19 |
| +3 |  6 | 28 | 270 | 69.16 | {9,6,3,0,...} | +19..+28 |