The moment is near. The last of the many steps that will lead us to open our eyes even more to the cosmos in which we live, has been to cool down its instruments. MIRI, an infrared instrument developed by NASA and ESA, was the last to achieve this (after reaching -266º C, the perfect temperature for this tool).
MIRI came last because it’s the instrument most sensitive to the dark current, so it has to be cooler than the other instruments to completely eliminate that effect , according to NASA.
Now, as the mirrors of the James Webb Telescope slowly cool to their final operating temperatures, the team responsible prepares for the thermal stability test. We are in the final phase of commissioning of all the scientific instruments in which all the modes and operations of each of them will be tested: MIRI (Mid-Infrared Instrument), the mid-infrared light instrument; NIRCAM (Near-Infrared Camera), an infrared camera with spectral coverage that goes from the edge of the visible to the near infrared; NIRSPEC (Near-Infrared Spectrograph), the near-infrared spectrograph and NIRISS/FGS (Near-Infrared Imager and Slitless Spectrograph/Fine Guidance Sensor), the near-infrared imager and orientation sensor.
When scientists point the telescope at an astronomical target, the telescope and sunshield will move together . The angle that the hood makes with respect to the Sun is called the orientation ‘attitude control system’ and the amount of waste heat that passes through the 5-layer hood to the main mirror will depend on this ‘attitude’.
According to NASA, during this last stage of instrument commissioning “we will do an astrometric calibration for each instrument , measuring the tiny optical distortions in the instrument to map each pixel in the detector to the precise location in the sky that it will see. We will measure the sharpness of stellar images at each point in an instrument’s image to enable optimal extraction of scientific information. We will demonstrate target acquisition for coronagraphy and spectroscopy, and test some special types of observations, including targets within our solar system and time-series observations of exoplanet transits .”
The telescope was sent to the Lagrange point L2 which is located 1.5 million kilometers from our planet, directly on the Earth-Sun line.
Webb’s infrared capabilities are critical as they will allow us to see, study and understand the very beginning of star formation. We are waiting to see it work at full capacity.
