Sometimes we see discussions on whether or not a satellite can be called an "amateur satelite".
This is what the 2023 edition of the ITU Handbook on Small Satellites says:
"5.4 Amateur-satellite missions
Amateur-satellite missions use satellites “self-training and communication”, with no pecuniary interest and could be categorised under three broad types: • Amateur missions that allow for two-way communications including transponders and repeaters among others. • Amateur missions that might provide useful technology for future amateur missions. • Amateur‐educational missions where there is an amateur interest, not necessarily involving two‐ way communications, exposing students in Science, Technology, Engineering and Mathematics (STEM) projects with the aim to encourage these students to enter a career in a STEM topic.
Key points are that the mission must be related to radio technique, and that the mission will not offer a pecuniary interest. The mission must relate in some way to the advancement and understanding of the technical and operational aspects of radio and satellite systems and are relevant to the amateur and amateur-satellite services. This excludes more general science payloads within missions like earth-observation, biology, wildlife tracking, geology, etc. which should be operated under other radiocommunication services because they are not related to radio technique. Furthermore, any mission that proposes any sort of pecuniary (monetary or financial) return is specifically excluded from amateur and amateur-satellite service bands.
Radio technique means having a reasonable possibility of application to radio communication systems operated in the amateur satellite service. Missions that are classified as amateur-educational might study aspects within the following topics: • Radiocommunication modulation methods and transmission protocols • Attitude determination and control systems • Command and control procedures • Radio receivers, transmitters and transponders • Satellite antennas systems • Sensors to study spacecraft performance • Power controls and supplies for use in space • Spacecraft computers, memory, operating systems, programs and related items • Radiation effects on electronic components • Radio wave propagation • Meteor trail reflection and other sporadic propagation mechanisms • Measurements of the orbital environment • Solar panel technologies • Software Defined Radios • Radiation tolerant electronics • In-orbit spacecraft software updates.
Technology developed and information acquired by missions studying the above topic have direct relevance to the advancement of the amateur-satellite service.
Satellite missions that are purely amateur include: • Linear transponders or FM repeaters for voice or data communications • Digital voice repeaters • Transmission of images using appropriate analogue or digital standards • Amateur Packet Reporting System (APRS) transmissions • Microwave beacons • Digital Store-and-forward bulletin boards and global messaging systems.
Transmission of telemetry alone and without additional mission components is generally an insufficient reason for a mission to be considered for operation within frequency bands allocated to the amateur-satellite service."
73, Nico PA0DLO