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jon_hendry t1_je76ti4 wrote

JWST sees in infrared, not microwave, so while it can “see further into the past” it can’t directly measure the CMB, which is microwaves.

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yofomojojo OP t1_je89pto wrote

Yeah, I'm realizing I have two contradicting notions in my head about that now. Is there still some sort of mapping being done, by any other name than CMB though? That thing we were all excited for a peak of about how the universe X billion years ago was shaped?

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Sharlinator t1_je9ldkl wrote

JWST is a narrow-field instrument, so it’s ill suited for survey type tasks; it would take an extremely long time to map some appreciable fraction of the sky, and anyway parts of the sky are out of its reach because of the need to remain behind the sunshade. But the NGRST, due to launch in 2026 or 2027, is designed specifically for surveys in visible light/near infrared. Its field of view is approximately the angular size of the full moon, which is an area about 100x larger than that of Hubble or JWST. Mapping the whole sky at that level of detail would still require a couple hundred thousand separate exposures!

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jarlrmai2 t1_je8uslz wrote

Maybe the SQA ground based radio telescope?

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mfb- t1_je7pt7h wrote

JWST doesn't measure in the wavelength range of the CMB, so I'm not sure what you heard but it doesn't sound right. Here are three things that might be related:

JWST needed about half a year from launch to the first science images. That time was spent unfolding the telescope (~1 month) and calibrating it and its instruments.

JWST can only observe targets in a ring around the Sun/Earth direction, in the worst case you need to wait almost half a year until your target is in view.

[Planck](https://en.wikipedia.org/wiki/Planck_(spacecraft)) needed ~9 month to make a full-sky map of the CMB in 2009-2010 based on the way it scanned the sky and again the issue that you cannot measure too close to the Sun.

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