On-orbit thermal behaviour of the IRTS cryogenic system

✍ Scribed by G. Fujii; S. Tomoya; M. Kyoya; M. Hirabayashi; M. Murakami; T. Matsumoto; T. Hirao; H. Murakam; H. Okuda; T. Kanari

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 1013 KB
• Volume: 36
• Category: Article
• ISSN: 0011-2275
• DOI: 10.1016/0011-2275(96)00035-5

✦ Synopsis

The IRTS (Infrared Telescope in Space) was launched at 08:Ol on 18 March 1995 UT by the H-II rocket as a part of the Space Flyer Unit (SFU), which is a re-usable free flyer designed as a multi-purpose common facility for scientific and engineering experiments. The He II tank was estimated to be approximately 85% full at 1.84 K at the moment of launch, 11 h after pumping was disconnected and the tank was sealed. The vapour evacuation through a porous plug was resumed 28 min after the launch. The thermal state reached the anticipated steady state at 1.91 K on the third day without any anomalous thermal behaviour of the porous plug in the initial zero-g state. Over the course of 10 days the SFU transferred to a low earth orbit (LEO) at 486 km from the initial phase orbit at 340 km with the telescope aperture lid ejecting on day 11 after launch. A 3He refrigerator was then activated to decrease the temperature of some bolometer detectors down to 302 mK for observations in the far IR region. Every detector worked quite satisfactorily. The stable thermal state of He II at 1.91 K was maintained until the depletion of He II at 09:30 on 24 April UT. The cold life is found to be fairly close to the prediction on the basis of the ground test data. On April 27 the sun shield was jettisoned for the safe retrieval by a US shuttle in January 1996, and the IRTS mission was completed because of the regular shift of the SFU mission time-line to another experiment. In this report the flight data of the thermal performance of the cryogenic system are discussed.