There's also a lifetime issue. Say you decide, "forget the whole vibration thing, we'll run the cryocooler half the time and take data half the time while the cooler is powered off"
Then you either get half the mission data, or extend the mission by a factor of two, which means twice the operational labor cost, plus every other part of the craft has to be double lifetime rated, which could get expensive. Hubble used to burn thru gyros on a regular basis, so now you need them to last twice as long or launch with twice as many spares. Or maneuvering propellant if any, now you need twice as much for station keeping.
You can easily get painted into a corner where the cheapest way to run a mission twice as long is to launch two of them. At that point you're better off saying "you know the cryocool half the time and take data half the time idea? Yeah scrap that idea"
This is before we started on energy issues. A heavy helium tank doesn't use much energy. But cryocoolers on earth take quite a bit indeed, well, at least compared to a couple watt transmitter and all that. Whats heavier, a tank big enough to last mission lifetime, or a cooler and a stunning array of solar panels to run the cooler? Or since it only runs half the time as per above to prevent vibration issues, you could put a battery in which is heavy and becomes another exciting point of failure. This makes the existing power system more complicated and less reliable possibly shortening the theoretical craft lifetime to less than you'd get if you just launched a big simple tank.
How about just making a detachable LHe tank and send some replacement helium every few years? Shouldn't be too costly even given the day-to-day cost of running a space observatory.
Even worse the helium was the limiting consumable in this particular case, but for the next scope the last gyro might burn out in 5 years. So now you need a supply of gyros, more likely an entire nav unit bolted permanently on. And next time the battery croaks so you need a battery and a way to install it and isolate the old one such that you can never end up with neither installed. And next time the transmitter final power amp goes thru too many thermal cycles and cracks so you need a complete telemetry unit.
Yes I know there are good reasons why they put it at a L point, but unscheduled unplanned maint is exactly what the ISS could have been perfect for. Position this dude in the same orbit but at a phase 10 miles away so its not too close, and send a live astronaut with a new battery or whatever anytime "something" fails. To say the ISS project is not managed this way would be an understatement. But someday, an unscheduled repair shop in space will exist, and probably be quite profitable.
Then you either get half the mission data, or extend the mission by a factor of two, which means twice the operational labor cost, plus every other part of the craft has to be double lifetime rated, which could get expensive. Hubble used to burn thru gyros on a regular basis, so now you need them to last twice as long or launch with twice as many spares. Or maneuvering propellant if any, now you need twice as much for station keeping.
You can easily get painted into a corner where the cheapest way to run a mission twice as long is to launch two of them. At that point you're better off saying "you know the cryocool half the time and take data half the time idea? Yeah scrap that idea"
This is before we started on energy issues. A heavy helium tank doesn't use much energy. But cryocoolers on earth take quite a bit indeed, well, at least compared to a couple watt transmitter and all that. Whats heavier, a tank big enough to last mission lifetime, or a cooler and a stunning array of solar panels to run the cooler? Or since it only runs half the time as per above to prevent vibration issues, you could put a battery in which is heavy and becomes another exciting point of failure. This makes the existing power system more complicated and less reliable possibly shortening the theoretical craft lifetime to less than you'd get if you just launched a big simple tank.