Breaking news! NASA has announced that it has verified a JWST instrument. Why? See here

Credit image: STScI/NASA
Credit image: STScI/NASA

Article by: Andacs Robert Eugen, on 04 March 2022, at 04:39 am Los Angeles time

A NASA announcement shows that part of the team coordinating JWST has finished a verification of the telescope instrument, more precisely the Near-Infrared Spectrograph (NIRSpec). 

The Webb Near-Infrared Spectrograph (NIRSpec) team completed the initial verification of three key on-board mechanisms last week, belonging to NIRSpec, which is aboard the James Webb Space Telescope. 

These verifications, on the instrument to which ESA (European space agency) contributed, were necessary according to NASA. Checks on these mechanisms are very important to make sure that Webb works perfectly and will be able to begin its observations this year. It's good to know that any element and mechanism of Webb will be verified by NASA.

Below you can read what engineers said about this instrument.

"To work properly as a spectrograph, NIRSpec has three mechanisms: a Filter Wheel Assembly (FWA), a Grating Wheel Assembly (GWA), and a Refocus Mechanism Assembly (RMA). The gratings in the GWA spread the incoming light over its colors or wavelengths to make a spectrum. The filters in the FWA block the wavelengths that are outside the range of interest to prevent contamination between different optical paths, or 'orders.' The RMA adjusts the instrument focus.

"We operated the Filter Wheel Assembly first, cycling it through all eight of its positions in both forward and reverse directions. Those eight filter wheel positions include five long-pass order-separation filters, two finite-band target acquisition filters, and an 'opaque' position that serves as the instrument shutter. At each position, we recorded a set of reference data. This data showed us how well the wheel was moving and how accurately it settled into each position. Between each FWA position, we downloaded 'high-capacity buffer' data from the positioning sensors, and the NIRSpec team analyzed the data. The data showed that the wheel moved very well even in the first attempt.

"We then used a very similar procedure for the Grating Wheel Assembly, which also performed excellently the first time. The GWA is shaped like a miniature Ferris wheel and holds eight optical elements, consisting of six diffraction gratings, one prism, and a mirror. These dispersers separate the incoming light by wavelength, generating spectra that are detected by NIRSpec's sensor chips.

"The Refocus Mechanism Assembly includes a linear translation stage that holds two flat mirrors. It will be used to fine-tune the instrument focus, compensating for any change in the overall focus position of the Webb telescope that may occur throughout the observatory's lifetime. After various initial retrievals of the RMA telemetry acquisition chain, the mechanism was moved forward a few hundred steps from launch position. Just like with the FWA and GWA, we used high-capacity buffer readouts to collect reference datasets. After the initial move, we commanded the RMA mirrors to their previous best focus position; successful completions of this test showed us that the RMA is a well-behaved and healthy mechanism.

"In the coming months, the NIRSpec team will continue their commissioning efforts. The whole team is very much looking forward to the start of science observations this summer!"

The three engineers said --- Maurice Te Plate, Webb NIRSpec systems engineer, European Space Agency; Tim Rawle, Webb NIRSpec instrument scientist, European Space Agency; and Ralf Ehrenwinkler, project manager, NIRSpec post-delivery support, Airbus Defense and Space

We are waiting for the first observations and especially the following images of Webb! 

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