I get that part. The interesting part is if building a new instrument will be marginally more useful than resupplying the current one. A few years back there wa

I get that part. The interesting part is if building a new instrument will be marginally more useful than resupplying the current one. A few years back there was a demonstration of an orbital vehicle for refueling satellites. So, which is better: spending a few more billions for capturing a few more frequencies of infrared light or spending a few hundred millions for extending the life of the current mission.