To be honest I saw the first thing that popped up when I searched and thought it was interesting that it was something to do with satellite communications. But the rare earth elements is interesting also. I searched again and this ...

https://pubchem.ncbi.nlm.nih.gov/compound/iridium

A metallic element with the atomic symbol Ir, atomic number 77, and atomic weight 192.22.

Iridium atom is a cobalt group element atom and a platinum group metal atom.

USES:

Alloy with platinum for ammonia fuel-cell catalyst, electric contacts and thermocouples, commercial electrodes and resistance wires, laboratory ware, extrusion dies for glass fibers, jewelry. Primary standards of weight and length. /The meter was intended to equal 10-7 or one ten-millionth of the length of the meridian through Paris from pole to the equator. However, the first prototype was short by 0.2 millimeters because researchers miscalculated the flattening of the earth due to its rotation. Still this length became the standard (the platinum-iridium alloy called the "1874 Alloy.") In 1889, a new international prototype was made of an alloy of platinum with 10 percent iridium, to within 0.0001, that was to be measured at the melting point of ice. In 1927, the meter was more precisely defined as the distance, at 0 deg, between the axes of the two central lines marked on the bar of platinum-iridium kept at the BIPM, and declared Prototype of the meter by the 1st CGPM, this bar being subject to standard atmospheric pressure and supported on two cylinders of at least one centimeter diameter, symmetrically placed in the same horizontal plane at a distance of 571 mm from each other. The 1889 definition of the meter, based upon the artifact international prototype of platinum-iridium, was replaced ... in 1960 using a definition based upon a wavelength of krypton-86 radiation. (See http://physics.nist.gov/cuu/Units/meter.html for a discussion of the platinum-iridium bar as the historical standard of length.)