A European armed force or national meteorological service that decides to maintain its own upper-air observations is not making one purchase. It is making three, on three different clocks, in three different markets, and with three very different degrees of freedom. The first purchase is of something consumed and destroyed at every use: a balloon, a length of cord and an instrument package that ascends once, transmits for a couple of hours and is gone. That layer is replenished continuously, it appears in the accounts as recurring expenditure, and it looks, on the face of it, like the most competitive part of the chain. The second purchase is of durable equipment: a receiver, the device that prepares and checks the instrument before release, the processing software and, increasingly, an automated launcher. That layer is bought rarely, lives for a decade or more, and is supported by maintenance arrangements that outlast the officials who signed them. The third is not a purchase at all but a standard: the format in which the finished observation leaves the system and enters national and international exchange.