This stamp has a hidden date on the earth's sphere on the right side of the stamp.
Alouette II, the focus of the design used on this stamp, is Canada's newest satellite. It was launched recently from a site in California, and was designed to augment and extend the work of the first Canadian satellite, Alouette I, which was launched on September 29th, 1962 and is still operating. Alouette II has been substantially modified to provide added reliability and for adaption to a new orbit. While Alouette I followed a circular orbit, the path of Alouette II is elliptical, and is substantially higher at certain points that its predecessor. The Canadian satellites have four primary purposes; to measure the hour-to-hour electron densities of the ionosphere directly below the satellites, to determine the electron densities at the height of the satellites, to listen to the very-low-frequency noise in the frequency range of 1 to 10 kc/s and to measure primary cosmic ray particles outside the earth's atmosphere, including electrons, protons and alpha particles. An additional experiment has been designed by the United States National Aeronautical and Space Administration for Alouette II. It involves an electron probe to determine the temperature of electrons in the vicinity of the orbiting satellite. Alouette II's two antennas have been developed to do these particular jobs. One measures 240 feet from tip to tip, the other 75 feet.