A dedicated satellite, or a hosted payload?

A hosted payload skips most of a program: no bus procurement, no launch campaign of your own, no fleet operations. Your instrument rides on a spacecraft that was going to orbit anyway, and you pay for a slice of its power, pointing and downlink. For a first instrument, a science mission or a technology proof, this is often the fastest and cheapest path to flight heritage that exists.

The model is mature. Commercial and governmental operators sell hosting as standard practice, and the interfaces are well understood. Nothing about it is exotic.

The orbit, first of all. Your payload flies where the host's mission needs to be, at the host's local time, for the host's lifetime. If your instrument wanted a different plane or a different revisit, that preference lost the argument before it was made.

The schedule, second. Host spacecraft slip for host reasons, and your payload waits with everyone else's. And third, the jurisdiction: the spacecraft is commanded from the host's control centre, under the host's licences, subject to the host's government. In an ordinary year none of this matters. The catalogue of interference cases we maintain is a record of the years that were not ordinary.

Ask one question: does the mission still make sense if a foreign operator can see its tasking, schedule its downlink and, in the worst case, switch it off? For a scientific radiometer, usually yes. For an experimental communications transponder, often yes. For an imaging payload over your own territory, or a communications payload carrying government traffic, the question answers itself.

There is also a quieter cost. A hosted payload builds instrument experience but not program experience. The operators, ground stations and procedures that a dedicated mission forces into existence are exactly the assets a national program needs next, and hosting defers them.