{"id":28965,"date":"2022-02-10T00:00:00","date_gmt":"2022-02-10T00:00:00","guid":{"rendered":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/?post_type=purple_issue&p=28965"},"modified":"2022-03-23T13:15:41","modified_gmt":"2022-03-23T13:15:41","slug":"waking-up-webb","status":"publish","type":"post","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/2022\/02\/10\/waking-up-webb\/","title":{"rendered":"Waking up Webb"},"content":{"rendered":"\n

The James Webb Space Telescope\u2019s launch and deployment was a storming success, but why haven\u2019t we seen the first pictures yet? Govert Schilling <\/strong>has the answer<\/p>\n\n

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The most powerful space telescope launched into space, JWST is a worthy successor to Hubble<\/figcaption><\/figure>\n\n
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After 25 years and over 10 billion US dollars, on Christmas Day 2021, the James Webb Space Telescope (JWST) was finally launched into space by a European Ariane 5 rocket. With its 6.5-metre primary mirror and its tenniscourt-sized sunshield, Webb had to be folded up to fit in the rocket\u2019s fairing, only to be deployed step by step in the first two weeks of its mission. However, the successor to the Hubble Space Telescope won\u2019t take its first images of the Universe before late June or early July 2022, which begs the question \u2013 why?<\/p>\n\n

It seems like an excessively long wait, especially since JWST arrived in its final orbit on 24 January. A total of three mid-course correction manoeuvres successfully placed the huge space telescope in a slow looping orbit around the second Lagrange point (L2), a stable gravitational point some 1.5 million kilometres behind Earth as seen from the Sun. \u201cBut a lot more needs to be done before we can start science operations,\u201d says Mark McCaughrean, the Senior Advisor for Science and Exploration at ESA (the European Space Agency), NASA\u2019s main partner in the programme.<\/p>\n\n

For one, the telescope and its sensitive instruments, which left the French Guiana launch platform at tropical temperatures, have to cool down to 230\u02daC below zero. <\/span>Thanks to its giant multi-layer sunshield, JWST had already reached \u2013200 \u00b0C by early January, but the passive cooling slows down over time. It\u2019s a delicate process, says McCaughrean. For instance, the optics can never be the coldest parts of the telescope, lest molecules being released as gases from the graphitecomposite support structure freeze down on the mirrors, degrading its performance.<\/p>\n\n

When the NIRCam instrument (Near Infrared Camera) got cold enough for its sensitive mercury-cadmium-telluride detectors to pick up infrared light, the process of aligning the telescope\u2019s 18 mirror segments could finally commence. Each hexagonal segment is fitted with seven actuators and can be slightly tilted, shifted, rotated and deformed to ensure that they operate together as one perfect parabolic surface. And since the alignment procedure is done with starlight, it marks JWST\u2019s \u2018first light\u2019. But it will take months of incremental precision adjustments before the 18 individual stellar images from each mirror are all brought together into one single focus.<\/span><\/p>\n\n

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Instrument testing<\/strong><\/h5>\n\n

Around late April, engineers will also start commissioning JWST\u2019s four large science instruments: NIRCam (Near InfraRed Camera), NIRSpec (Near InfraRed Spectrometer), MIRI (Mid InfraRed Instrument (see box), and the Canadian FGS\/NIRISS (Fine Guidance Sensor\/Near InfraRed Imager and Slitless Spectrograph). Equipped with beam splitters, filters and micro-shutters, all have different observing modes, and these have to be fully tested and calibrated before they are handed over to the astronomy community. \u201cOf course, every instrument has been tested and checked on Earth,\u201d says McCaughrean, \u201cBut we need to prove that they also perform flawlessly in space.\u201d<\/span><\/p>\n\n

So what about that supposedly aweinspiring first picture taken by the new space telescope? Well, that\u2019s not expected until some six months after launch, which would be late June or early July. And according to McCaughrean, \u201cWhat it will show is a closely guarded secret. Most likely some kind of star-forming region.\u201d<\/p>\n\n

Then again, he imagines that NASA may eventually decide to release an earlier test or alignment image at some time. \u201cThe longer it takes, the more people will start to believe something must be broken. There may even be political pressure on NASA to put something out at an earlier stage \u2013 they\u2019d better prepare for this.\u201d<\/span><\/p>\n\n

Anyway, the first round of science observations won\u2019t start before summer. Astronomers can\u2019t wait to train their new, expensive toy on their favourite objects, be that a remote galaxy at the dawn of time, a planet-spawning circumstellar disc, an exoplanet\u2019s atmosphere, or a denizen of our own outer Solar System.<\/span><\/p>\n\n

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With more fuel left over after its precision Ariane 5 rocket launch, JWST can stay in orbit at L2 for much longer than anticipated<\/figcaption><\/figure><\/div>\n\n
Field of regard<\/strong><\/h5>\n\n

Webb has less pointing flexibility than Hubble: since the telescope must face away from the Sun to keep its instruments consistently cool, its \u2018field of regard\u2019 will cover 40 per cent of the sky on any given day, and it will take around six months to access the whole of the sky.<\/p>\n\n

The good news is that JWST\u2019s midcourse corrections used up less fuel than expected, which means there\u2019s more left to keep the space telescope in its L2 orbit. As a result, its operational lifetime may be extended beyond the projected operational period of 10 years. In any case, the exciting results Webb is bound to deliver will make up for the half-year wait we\u2019re experiencing right now.<\/span><\/p>\n\n

<\/p>\n\n

<\/p>\n\n

<\/div>
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Unfolding a space telescope<\/strong><\/h4>\n\n\n\n

It took more than 50 individual steps and two weeks to set JWST up<\/strong><\/p>\n\n\n\n

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Europe’s place on Webb<\/h4>\n\n

Led by the UK, European partners built one of JWST\u2019s main instruments<\/strong><\/p>\n\n

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MIRI (left) being integrated into JWST\u2019s science payload module at NASA\u2019s Goddard Space Flight Center in 2013<\/figcaption><\/figure>\n\n

MIRI (Mid Infrared Instrument) is the major European contribution to Webb, apart from the Ariane launch. A camera and spectrometer combined, it was designed and built by a 10-country European consortium led by the UK, in collaboration with NASA.<\/p>\n\n

MIRI\u2019s high spectral resolution enables it to identify a huge range of molecules in star-forming regions, protoplanetary discs and exoplanet atmospheres. The instrument\u2019s principal investigator is Professor Gillian Wright of the UK Astronomy Technology Centre, Edinburgh.<\/p>\n\n

\u201cMIRI\u2019s capabilities cannot be achieved by ground-based telescopes,\u201d she says. \u201cThe Earth\u2019s atmosphere is too efficient at blocking mid-infrared wavelengths. <\/span>Uncooled telescopes on Earth also emit their own mid-infrared light; for them to do MIRI\u2019s work would be like looking for a match with a telescope that\u2019s on fire. Webb is cold and far beyond Earth\u2019s atmosphere, making MIRI hundreds of times more sensitive than any other instrument like it.\u201d<\/p>\n\n

To be this sensitive, MIRI has to be cooled to 6.7\u00b0C above absolute zero, or \u2013266.5 \u00b0C. Since JWST\u2019s sunshield will only provide temperatures as low as \u2013230\u00b0C, the instrument also has a cryo-cooler, which acts like a refrigerator. A set of four coronagraphs enables the study of extrasolar planets without being \u2018blinded\u2019 <\/span>by the radiation of the planets\u2019 host stars.<\/p>\n\n

MIRI was Webb\u2019s first instrument to be completed and was integrated with the JWST in the US in 2013, after a final round of tests at the Rutherford Appleton Laboratory in Oxfordshire.<\/p>\n\n

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Govert Schilling is an astronomy journalist and broadcaster, and author of Ripples in Spacetime <\/p>\n<\/div>\n<\/div>\n\n

Photos: ILLUSTRATION, NASA\u2019S GODDARD SPACE FLIGHT CENTER X 10, JUAN RUIZ PARAMO\/ISTOCK\/GETTY IMAGES, NASA\/CHRIS GUNN, DETLEV VAN RAVENSWAAY\/SCIENCE PHOTO LIBRARY, ARIANESPACE\/ESA\/NASA\/CSA\/CNES<\/p>\n","protected":false},"excerpt":{"rendered":"

JWST\u2019s launch was a success, but why haven\u2019t we seen any pictures yet?<\/p>\n","protected":false},"author":24,"featured_media":28960,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"ub_ctt_via":"","purple_page_number":"34","purple_custom_meta_purple_page_number":"34","purple_seq_number":"1","purple_custom_meta_purple_seq_number":"1","purple_source_article":"article_34-1.xml","purple_custom_meta_purple_source_article":"article_34-1.xml","purple_source_issue":"March-2022","purple_custom_meta_purple_source_issue":"March-2022","purple_external_id":"March-2022-34-1","purple_custom_meta_purple_external_id":"March-2022-34-1","purple_issue_code":"|0000086550||","purple_custom_meta_purple_issue_code":"|0000086550||","purple_android_product":"com.im.skyatnight.202","purple_custom_meta_purple_android_product":"com.im.skyatnight.202","purple_ios_product":"com.im.skyatnight.202","purple_custom_meta_purple_ios_product":"com.im.skyatnight.202","purple_web_product":"","purple_custom_meta_purple_web_product":"","purple_publication_id":"075fab74-0a21-4201-866a-899d6c41c40c","purple_migrated":"","kt_blocks_editor_width":""},"categories":[21],"tags":[14],"featured_image_src":"https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/02\/5b5610dc-87c4-4299-8a39-eb59b8e0508b.jpg","author_info":{"display_name":"importmanagerhub@sprylab.com","author_link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/author\/importmanagerhubsprylab-com\/"},"acf":{"readingTimeMinutes":"6","apple_news_title":""},"uagb_featured_image_src":{"full":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/02\/5b5610dc-87c4-4299-8a39-eb59b8e0508b.jpg",1946,2048,false],"thumbnail":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/02\/5b5610dc-87c4-4299-8a39-eb59b8e0508b-150x150.jpg",150,150,true],"medium":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/02\/5b5610dc-87c4-4299-8a39-eb59b8e0508b-285x300.jpg",285,300,true],"medium_large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/02\/5b5610dc-87c4-4299-8a39-eb59b8e0508b-768x808.jpg",768,808,true],"large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/02\/5b5610dc-87c4-4299-8a39-eb59b8e0508b-973x1024.jpg",800,842,true],"1536x1536":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/02\/5b5610dc-87c4-4299-8a39-eb59b8e0508b-1460x1536.jpg",1460,1536,true],"2048x2048":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/02\/5b5610dc-87c4-4299-8a39-eb59b8e0508b.jpg",1946,2048,false]},"uagb_author_info":{"display_name":"importmanagerhub@sprylab.com","author_link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/author\/importmanagerhubsprylab-com\/"},"uagb_comment_info":0,"uagb_excerpt":"JWST\u2019s launch was a success, but why haven\u2019t we seen any pictures yet?","_links":{"self":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/28965"}],"collection":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/users\/24"}],"replies":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/comments?post=28965"}],"version-history":[{"count":8,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/28965\/revisions"}],"predecessor-version":[{"id":29727,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/28965\/revisions\/29727"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media\/28960"}],"wp:attachment":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media?parent=28965"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/categories?post=28965"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/tags?post=28965"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}