The second set in a series of three issues of Russian stamps commemorating the International Geophysical Year (IGY). The stamps were issued on 29 July, 1958, but the covers here were postmarked on 30 July, 1958 to mark the first day of the CSAGI Assembly in Moscow ("Opening of the 5th Meeting of the Special Committee for the IGY 1957/58").
Meteorology - This stamp shows a telemeter antenna pointing towards (and probably communicating with) the weather instrument being carried aloft by a weather balloon. The text to the right of the antenna reads "Radio-theodolite 'Malachite'" in Russian. The text in the label-box to the left of the weather balloon reads "Meteorology" in Russian.
Geomagnetism - This stamp shows a three-masted schooner sailing on the high seas. The name of this ship is printed below its bow and reads "Non-Magnetic schooner 'Zarya'" in Russian. To the left of these words is an instrument believed to represent the magnetometer used to record the Earth's magnetic field strength during the ship's voyage. The text in the label-box above the ship reads "Geomagnetism" in Russian.
Aurora - This stamp shows a curtain of aurora borealis (or aurora australis) in the night sky above ice floes on the Earth's surface. The instrument measuring this phenomenon is labeled with text just to its right. The text reads "Photo Camera, S-180" in Russian. The text in the label-box above the aurora reads "Study of Polar Glow" where "polar glow" is the Russian way of saying aurora.