Maximum precision for a new look to the universe

The observatory Alma, in the desert of Atacama north of Chile, is the most powerful radio telescope, and the terrestrial observatory more complex of the world. With Alma, shortening of ‘Atacama Large Millimeter/Submillimeter Array', the astronomers have like aim investigate remote galaxies and look for the basic components of solar systems and planets habitables. The construction of the observatory still has not finalised, and the first images, of an unexpected precision, have caused already furor to world-wide level.

To date have erigido on the desértica plateau to 5.000 metres of height roughly a third of the total of 66 radius-planned antennas. Alma does not use an only antenna to observe the cosmos, but diverse receptors positioned of precise form and interconnected between yes to form an only telescope. Alma-Correlator, one of the supercomputadores skilled faster of the world, processes the data of the images of the antennas to produce a global image.

angular Systems of measure

designates typically angular system of measure to devices of measure with a better precision of ±5 angular seconds and with more than 10.000 lines. These angular systems of measure employ in applications that require a highly precise measurement of angles in the rank of few angular seconds, as for example in rotary tables and cabezales basculantes of machines tool, axes C of lathes, and also in devices of measurement and in telescopes.

The attachment of the antennas to produce a gigantic telescope allows to Alma capture images of celestial bodies that find to several million years light of distance. For this is determinante the precise positioning of the antennas that weigh several tonnes. The most minimum imprecision falsea the result and drives to images no nítidas.

For the 25 European antennas, the managers decided by angular systems of measure of Heindenhain. This company of Traunreut, in Alta Baviera (Germany), develops and produces angular systems of measure from does almost 60 years, and is thus pioneering in this field. His extraordinary precision of measurement and his high stability on a long-term basis guarantee in Soul the precision required for the alineamiento of the antennas.

The special strong point of the angular systems of measure of Heindenhain resides in his excellent precision inside a period of signal. These systems work without contact, being thus especially indicated for his employment in devices of precision.

For the alineación exact of the horizontal angle (azimut) the European antennas of Alma use the new angular system incremental of measure WAS 7480C with 247.800 lines on the rule and a diameter of 3155 millimetres. The ERA 7480C was made specifically for his use in Alma, and the length of the strip was adapted of precise form to the diameter required. The precision alcanzable was simulated with antelación like part of the development of the project. The angular systems of measure of the range WAS 7000 compose of the cabezal captador and a strip of steel of a stretch like support of the graduation.

The vertical angle (elevation) adjust it the researchers in Chile with help of the angular system of measure Heindenhain WAS 4282C. The especially precise angular system of measure of the range WAS 4000 with drum of graduation of steel has 32.786 lines of graduation and a diameter of 209 millimetres.

The electronics equipment dealers equipment dealers of interface of Heindenhain adapt the signals of the systems of measure to the interface of the subsequent electronics equipment dealers equipment dealers. The new external box of interface EIB 749 interpola and compensates the signals of exit of the cabezales captadores. The values of position are issued through Ethernet to the computer of control of the antenna.

Principle of measurement

The angular systems of measure Heindenhain use supports of measurement to base of regular structures called graduations. Like material of support for these graduations employ substrates of glass or of steel.

In the method of incremental measurement, used also in the space telescope Alma, the graduation composes of a reticular structure regulate. The information of the position obtains explaining the individual increases (steps of measurement) from a point zero situated to will. Since for the determination of positions requires an absolute reference, the support of measurement has of a second track with the calls mark of reference encoded in distance. The absolute position of the rule, established by means of the marks of reference, is assigned exactly to a step of measurement.