ARRGEN

Examples

1. Create User-Specified Array on Moon

% arrgen
  Radius     = 1738000
  LATitude   = 0:00:00
  LONgitud   = 0:00:00
  NSTAT      = 12
  EWoffset   =   0.0000,  452.7406, -498.3997,     403.3182, -208.2298,
              -402.4793, -454.2729,    0.55871205, 207.2576,  497.9849,
	       295.9012, -292.7386

  NSoffset   = 500.0000,  212.1913,   39.967656, -295.5227, 454.5767,
	      -296.6645,  208.8913, -499.9995,    455.0205,  44.839311, 
	      -403.0411, -405.3441
  OUTPUT     = "STATIONS"
  ARRNAMe    = "LUNAR"
  ZENANG     = 85.0
  /

2. Generate WYE Array on Moon

% arrgen
  Radius     = 1738000
  LATitude   = 0:00:00
  LONgitud   = 90:00:00 WEST
  NSTAT      = 12
  DIAMETER   = 1
  ROTATE     = -5
  OUTPUT     = "STATIONS"
  ARRNAMe    = "WYE"
  ZENANG     = 85.0
  ARRTYPe    = "WYE"
    ARRDIAM    = 1000
    EXPON      = 1.716
  XYPLOT
    PLOTFILE = wyearr.plt/ps
    LINEWIDTH=1
    DOTSIZE  =5
    MARK     =-1
  /

Parameters

R = x                                   [ 637000 ]
LAT = dd:mm:ss                          [ 00:00:00 ]
LON = dd:mm:ss                          [ 00:00:00 ]
EAST, WEST                              [ EAST ]
NSTAT = n                               [ 2 ]
OUTPUT = "filename"                     [ "STATIONS" ]
ARRNAM = "arrayname"                    [ "ARRAY" ]
ZENANG = x                              [ 89.90 ]
ROT    = x                              [ 0.0 ]
ARRTYP = "arraytype"                    [ "SPECIFY" ]
  EW = x1,x2,x3,...                     [ compulsory if ARRTYP="SPECIFY" ]
  NS = y1,y2,y3,...                     [ compulsory if ARRTYP="SPECIFY" ]
  ARRDIAM = x                           [ -1 ]
  EXPON   = x                           [ 1.0 ]
  RINGORD = n                           [ 3, i.e., a WYE array ]
XYPLOT                                  [ default is no plot ]
  PLOTF  = "filename/plottype"          [ compulsory if XYPLOT is true ]
  DIAM   = x                            [ 0.0 ]
  MARK = n                              [ -1, i.e. a dot ]
  LINEW = n                             [ 1 ]
  FONT = n                              [ 1, i.e. a simple font ]
  DOTSIZE = n                           [ default is LINEWidth ]

Discussion

The user has three choices of how to generate the coordinate offsets -- controlled by the parameter ARRTYP:

• If ARRTYP="SPECIFY", the offsets (in meters) of each station's coordinates from the latitude and longitude of the array center must be specified. At least two stations must be listed in this case.
• If ARRTYP="WYE", a three-armed wye array is generated, with one arm pointing toward the north. If NSTAT is not divisible by 3, the odd telescopes are distributed counterclockwise at the outermost positions starting on the north arm. Along each arm, the telescopes are placed at distances from the array center proportional to N**EXPON, where N is the ordinal telescope number along the arm, in such a way that the entire array has a diameter of ARRDIAM in meters.
• If ARRTYP="CRING", a crystalline (or Cornwell) ring set is generated. The order of the ring is given by RINGORD; the maximum for RINGORD is 12 at present. If NSTAT=RINGORD, a simple crystalline ring is generated. If NSTAT < RINGORD, an incomplete ring is generated starting with the northernmost position and maximizing the baselines between subsequent telescopes. If NSTAT > RINGORD, two or more concentric rings are generated, with the telescopes in each ring lying along radial arms. If NSTAT is not evenly divisible by RINGORD, the odd telescopes are distributed by maximizing the baselines between outer telescopes; the first odd telescope is placed on the northernmost arm. As with the wye array, the placement of telescopes along each arm is determined by parameter EXPON, with the distance being proportional to N**EXPON and the entire array having the diameter of ARRDIAM meters. Setting RINGORD to 3 produces almost identical results to the wye array above.

In the output STATIONS file there are NSTAT lines, and each station name is formed from the first 5 characters of the ARRNAM parameter. (In the first example above, the stations would be LUNAR-1, LUNAR-2, etc.) All telescopes are assumed to have an ALTAZ mount with the zenith angle limit given in degrees by ZENANG.

The algorithm for placing the telescopes on the planet surface lays out the array in a plane tangent to the point (R,LAT,LON) on the surface of the planet and then projects the telescopes radially down to the surface. (The infinite plane is mapped to a hemisphere centered at LAT and LON.) As such, ARRGEN is most useful for arrays which are small compared to the radius of the planet.

An XY plot of the stations can be created on the PGPLOT file given by PLOTF. The snapshot (u,v)-coverage for a source at the zenith is also plotted on the same page. The (u,v) positions are in meters and are computed after the stations are projected onto the planet's surface. Parameters affecting the plot are: the symbol used for plotting each (u,v) point (MARK), the width of the border and other lines (LINEWidth), the FONT used (1=simple, 2=roman, 3=italic, 4=script), and the pen size for the drawing symbols (DOTSIZE). To test the consistency of the telescope spacing, the user can specify the DIAMeter of each telescope, resulting in appropriately-scaled circles at the position of each array element in the XY plot.

History