Astrophilately

Soviet 1978 stamp commemorating Vladimir Kovalyonok and Aleksandr Ivanchenkov's new space-endurance record of 140 days onboard Salyut 6
One of the so-called "Sieger covers" that were taken to the Moon and back by the US astronauts flying the Apollo 15 mission

Astrophilately is a branch of philately which deals with the collection of stamps and postmarked envelopes related to spaceflight. It is the intersection of space and postal history. Covers cancelled on the date and at a post office near the controlling agency are used in postal exhibits to share the development and conquest of the cosmos.