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VLTI Station Position Technical Data

Observatory Location

The VLTI comprises an array of stations which may be occupied by the commissioning sidereostats, 1.8 m auxiliary telescopes or the 8.2 m unit telescopes. The layout of these stations defines the VLTI array. The sidereostats and auxiliary telescopes may be relocated to any non-unit-telescope station. The unit telescopes may not be moved.

The physical location of the array centre is defined as follows: 

   Longitude: -70.40479659 degrees
    Latitude: -24.62794830 degrees

Station Position Coordinates

Following is a list of the station platform coordinates. The platform coordinates (p,q) are rotated from the geographic grid coordinates (e,n). This platform rotation, nu, defined as a clockwise rotation from geometric north (i.e. east = +90 degrees), is: 
   nu  =  -18.984 degrees
The geographic coordinates may be derived by rotating the (p,q) coordinates: 
   e  =  p * cos(nu)  +  q * sin(nu)
   n  =  q * cos(nu)  -  p * sin(nu)
where positive e is defined as the distance to the geometric east of the array centre and positive n is defined as the distance to the geometric north of the array centre.

Each station is allocated an letter-digit identifier for easier specification, e.g. "A1".

The following data is the station identifier, plus the coordinates of that station in the reference frame of the rotated platform, followed by the coordinates of the station as per an East-North grid, all specified in metres. 

_ID_______P__________Q__________E__________N____
 A0    -32.001    -48.013    -14.642    -55.812
 A1    -32.001    -64.021     -9.434    -70.949
 B0    -23.991    -48.019     -7.065    -53.212
 B1    -23.991    -64.011     -1.863    -68.334
 B2    -23.991    -72.011      0.739    -75.899
 B3    -23.991    -80.029      3.348    -83.481
 B4    -23.991    -88.013      5.945    -91.030
 B5    -23.991    -96.012      8.547    -98.594
 C0    -16.002    -48.013      0.487    -50.607
 C1    -16.002    -64.011      5.691    -65.735
 C2    -16.002    -72.019      8.296    -73.307
 C3    -16.002    -80.010     10.896    -80.864
 D0      0.010    -48.012     15.628    -45.397
 D1      0.010    -80.015     26.039    -75.660
 D2      0.010    -96.012     31.243    -90.787
 E0     16.011    -48.016     30.760    -40.196
 G0     32.017    -48.0172    45.896    -34.990
 G1     32.020   -112.010     66.716    -95.501
 G2     31.995    -24.003     38.063    -12.289
 H0     64.015    -48.007     76.150    -24.572
 I1     72.001    -87.997     96.711    -59.789
 J1     88.016    -71.992    106.648    -39.444
 J2     88.016    -96.005    114.460    -62.151
 J3     88.016      7.996     80.628     36.193
 J4     88.016     23.993     75.424     51.320
 J5     88.016     47.987     67.618     74.009
 J6     88.016     71.990     59.810     96.706
 K0     96.002    -48.006    106.397    -14.165
 L0    104.021    -47.998    113.977    -11.549
 M0    112.013    -48.000    121.535     -8.951

 U1    -16.000    -16.000     -9.925    -20.335
 U2     24.000     24.000     14.887     30.502
 U3     64.0013    47.9725    44.915     66.183
 U4    112.000      8.000    103.306     43.999
The stations U1, U2, U3 and U4 are occupied by the unit telescopes.

Note that due to restrictions of the delay lines and optical feed paths, not every arbitrary pair of stations may be chosen.

Station Map

VLTI station layout Click on the image icon to see the large-scale version (72kbytes) of the map displaying the station positions at the Paranal Observatory site.

Baseline Data

Here are two links to lists of baseline data. These give the stations used, the baseline length in metres and the baseline position angle in degrees clockwise from geometric north (i.e. due east = +90 degrees). There are three lists; the first is sorted alphabetically by station combination, the second by baseline length, and the third is sorted by position angle.

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