At 15:20 on September 26, two cryo-coolers (P-54 and P-56) for cooling payload were turned on, and started to cooling ITMY.
Operation record of compressor immediately after turned on
P-54:
Supply pressure: 24.2~24.8 bar
Return pressure: 99~104 psi
P-56:
Supply pressure: 23.5~23.9 bar
Return pressure: 96~104 psi
Because of the change of strategies, ITMY cooling was postponed. So two cryocoolers for the payload were turned off again by Uchiyama-kun around 11:30(JST)
Because the temperatures of structures that are designed to be cooled by the cryocoolers for the payload (cooler 1/2 heads, cooling bars, heat link suspensions, and payload components) are all below 158K(at 50K head) before starting cooling, H2O outgassing is not expected, while nitrogen and oxygen are expected according to the EXC warming up experience.
Actually, just after stopping cryocoolers, the vacuum level at IYA/BS slightly increased from 4x10^-6 Pa to 5.6x10^-6 Pa (IYA case) but it was almost recovered within one hour. The reason why the BS side was recovered faster than IYA side is maybe because of the number of pumps.
