Comment: Re:Worked for 4 years. (Score 1) 204
The minimum design lifetime isn't the actual lifetime of the mission. I believe there is enough helium for three years, but the multistage cooler is designed to be able to run in the event of coolant loss. ASTRO-H replaces ASTRO-E2 which suffered a catastrophic coolant loss. There are more details here, but it's behind a paywall.