But they don't. Any experiment that has designers who don't mind it blowing up isn't really worth it, and is probably dubiously designed for launch to boot. The dummy payloads usually have devices in them to record all the data they can grab, but that's not mandatory. Goddard was happy if the chute deployed.
Copied from my response to this post elsewhere.
Now if I just remember where the rest of them are...
Copied from my response to this post elsewhere.
Now if I just remember where the rest of them are...