Tests cryogéniques sur le successeur de Hubble Telescope (en anglais)
The NASA Hubble Space Telescope (HST) has been orbiting the earth since 1990. It observes the near ultraviolet, visible, and near infrared spectra. It could last until 2030 2040 but a scientific successor, the James Webb Space Telescope (JWST) is scheduled for launch in the spring of 2019, in Kourou, French Guiana. JWST will observe infrared bands, which are preferred for studying high redshift and low temperature objects, objects generally older and farther away in the universe (like the first galaxies formed in the Universe, for example).
NASA engineers completed final cryogenic testing on JSWT in November 2017. The telescope had been sealed for 100 days in a 12 m diameter, 40 tonne door chamber at Johnson Space Center in Houston. The tests were designed to ensure the telescope functioned as expected in an extremely cold, airless environment akin to that of space. While the telescope was inside the chamber, engineers monitored it using thermal sensors and specialized camera systems. Indeed, the telescope will be kept extremely cold in space, in order to be able to detect the infrared light from all objects. JSWT and its instrument have an operating temperature of about 40 K (around -233 °C). It relies on a cryocooler to lower its temperature to less than 7 K (around -266 °C). The telescope is protected from heat and light by a five layer, tennis court sized sunshield that acts like a parasol. The sunshield divides the observatory into a warm, sun facing side (reaching temperatures close to 85 °C) and a cold side (-240 °C).
Source: Cryogenic Society of America