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Just two days after the release
of the first full-color images from the James Webb Space Telescope,
the Webb team released all of their calibration data
that was used during instrument commissioning.
It's all available for download at the Mikulski Archive for Space Telescopes.
Now, to be clear, these are the calibration images
that were used to test particular modes of the instruments.
They're not quite as nice and pretty as those used
for the early release observations,
and that's because those targets were chosen
specifically so that they'd make beautiful images,
and they were taken with at least three filters that allowed a dedicated team
to process those images and clean them up to make them ready for public release.
On the other hand, calibration targets were chosen to test
particular imaging or spectral modes of the individual instruments.
But that didn't stop astronomers from downloading the data
and doing their own image processing.
One of them was Andras Gaspar of the University of Arizona.
He put out this really cool thread on Twitter,
describing the MIRI instrument calibration images.
Andras is actually a member of Team MIRI, and he was on console at the space
Telescope Science Institute in Baltimore, helping to get MIRI ready for science.
Now, I've never commissioned a science instrument on board the James
Webb Space Telescope, and I'm going to bet that you haven't either.
So I thought it'd be cool to get together with Andras
and let him tell us about what it was like to commission
MIRI and describe the stories behind these images.
Now, I should caution that my audio is a little less than perfect,
but the good news is
that Andras does most of the talking and his audio is just fine.
So with that, let's learn about how MIRI was commissioned.
[Christian Ready] Andas, thank you so much for joining me today.
It's great to talk with you, and congratulations on on setting up
what I know is jokingly referred to as literally the coolest
instrument on board Webb, the Mid-Infrared instrument.
But I was wondering, you're part of the team MIRI, right?
And can you tell me what what Team MIRI means, exactly?
[Andras Gaspar] Well, Team MIRI is a very large team,
and it's an international collaboration.
We've got people from ESA
who were the main designers.
Many parts for MIRI were from the U.S.
and we've got a nice little team here at the U of A, and we've helped out from
testing flight spares at JPL all the way to helping out now during commissioning.
[Ready] What is commissioning like with MIRI?
[Gaspar] Well, MIRI started its commissioning activities
slightly later than all the other instruments, right?
We had to cool down all the way to seven
Kelvin while the other instruments started working earlier.
But we all got checked out early on.
We turned on, we we knew we were healthy, and then once the cooler
got us down to our operating temperatures, we could start getting data.
[Ready] When you saw those first images from MIRI,
the very first ones, like we in the public got to see, the alignment
field and all of the other instruments all have like really pretty spikey stars.
And then Mary had all this cool stuff in it, like all this gas and dust
and stuff like that.
What was that like, seeing that for the first time?
That must have been just a real thrill to see it for real, right?
[Gaspar] Yeah, so we got those first images, I think on April 12 or 13,
somewhere around that time, and it was just an alignment
field test on the Large Magellanic Cloud and the downloaded images,
and they were beautiful.
So we're already very happy.
Most of those were taken at 7.7 microns where those PAH
(polycyclic aromatic hydrocarbon) features just light up.
So that's what all of the other people got to see.
One of the fields we also took image at 5.6 microns.
These images came down on April 13th and we got really excited
and made the first color image.
We were really happy about it, and immediately told, "all right,
let's not share this
with too many people.
[chuckles] Yes, it's really, really pretty and we're happy, but
let's just enjoy it ourselves." [Ready] Were you tempted like
did you want to - because you're pretty active on Twitter -
did you just want to get out there and say, "look at this, look!"...you know?
[Gaspar] Oh yeah, yeah.
You know, [laughs] I think...but not just me,
I think everyone and all instrument teams were just ready to shout off
the mountain top just how amazing everything is working.
[Ready] So this is like a really nice array of all of these parts of the LMC,
what was going on here with all these different filters?
And so this is an exciting image and I think up to this point,
this is the only area of the sky that has been imaged with all nine MIRI filters.
This image set was taken to define
the flat field of the detector.
Determining a flat field for MIRI is rather difficult [laughs]
because anywhere you look, you're going to see some background levels like this.
So this observation was dubbed the "thousand points of light"
method for determining a flat field where a field was observed
where many stars but not too bright stars were available.
And this field was dithered around,
and we would measure the brightness of the stars
as they were dithered around the detector and see how they change.
And this would allow a smooth leveled-out flat field to be determined.
[Ready] So when you say that you dither, can you tell us what that means?
Like when you're moving the telescope just a little bit over,
are you taking another picture and what does that do for you exactly
when you move the telescope around like that?
[Gaspar] That's right.
So dithering is exactly how you describe, you move the telescope
to place the same astrophysical object on different pixels.
And there can be various reasons for doing this.
Here, we did this so we could determine the flat field, obviously.
But for other cases you may want a mosaic, you may want to study
how the detector responds, because not all pixels are meant to be the same.
[laughs] Well, they're meant to be, but they're not.
So there are many different reasons to dither around.
And we do it with MIRI, especially.
[Christian Ready] Hi, I just wanted to let you know
that you can download
these images from Andras' GitHub repository in full resolution.
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And now back to our chat with Andras. [Ad end]
[Ready] So you took this image of the Cat's Eye Nebula and it looks very familiar
and also at the same time very different from the Hubble Space Telescope image.
So tell me why you chose this particular target
and what you were hoping to do with MIR as part of the commissioning.
[Gaspar] So these detectors have a certain property
where if you place a bright object on it, even after
you remove the bright object, it's going to leave a little ghost behind.
Just like some LCD screens burn in after a while...not
the same process happens, but you still have a latent image of the detector.
So we had two different programs to test the detector's response to bright objects.
This one taken of the Cat's Eye Nebula, while super pretty [laughs],
the primary goal was not to study the Cat's Eye and see how nice it looks,
but to see how much time after taking this image, does
the latent image sort of decay down on its own?
It takes about half an hour for it to sort of disappear.
[Ready] So does that mean that every time you take an image of a bright target with MIRI,
you have to wait 30 minutes before you could take another bright image?
[Gaspar] So that's a really good question.
So this is one of the reasons why we do dithering.
If you take...I mean, most bright objects will not be extended this much.
And if you dither it around, you can sort of guarantee
that you don't place really bright sources on the same region again.
So we can combine those two observations into a nice looking image. But
this is sort of a problem for these types of detectors.
And the only solution that we really have is what's called annealing,
where we take the detector and we heat it back up.
So the operating temperature for MIR is around
7 Kelvin, and it gets heated up to 20 Kelvin.
Then the temperature falls back down to 7 Kelvin.
And during this process, the latent images are remedied and they're gone.
[Ready] It's hard to think about 20 degrees above absolute zero as being warm,
but that really is [Gaspar: It's hot!] yeah,
but that's hot for MIRI, [laughs] and that's that's so counterintuitive.
[Gaspar] That's right.
[Ready] What then would might be the risk of this procedure?
Is there any chance that the cooler might fail
and not be able to bring MIRI back to its operational temperature?
[Gaspar] As far as I know, the cooler doesn't change.
That's an internal electronics that actually heat up.
MIRI.
[Ready] That's really cool. This is rather pretty.
[Gaspar] It should be familiar, it's the original PR image just in color.
[Ready] And it also - we're also seeing a little bit more of the detector, aren't we?
[Gaspar] That's right.
So the small upper field is filled up, as you can see.
So that's a part of the detector where we have the 23 micron Lyot
coronagraphic area.
But that area can still be used for regular imaging
because the Lyot Coronagraph is basically just a little mask in there
that blocks the stellar light.
If you put the star behind it all around that area, you can still image,
so you can use it to take images.
[Ready] Oh, wow. So is that mask present?
We're just not seeing its effects because it's not sitting on top of a star?
[Gaspar] Well, and this is a combined image.
It's dithered around., so that gap was filled up by the dithering.
[Ready] That's really, really cool.
So tell me about what's going on with this beautiful image of a Seyfert galaxy?
[Gaspar] This is at 5.6 microns also.
And you can see the cross artifact jumping out of the nucleus there.
This was taken for an annealing test, the same as we've talked about before.
Bright image, but I think this was the one where we actually annealed,
and on the other one (the Cat's Eye nebula)
we just looked at how it disappeared after this one was taken.
And the annealing was done to see if it gets rid of the latent images.
[Ready] Obviously, what really jumps out is just how bright that nucleus is.
So this is a really active nucleus, is that correct?
[Gaspar] That's right.
It's a Seyfert galaxy, so they have active nuclei.
Only a small percentage of galaxies are like this.
And right, the Seyferts are different from quasars in the fact
that you can actually spatially resolved the galaxies around the nucleus.
[Ready] They're not as active as a quasar used to be,
but they're still pretty active and it doesn't really come across
in the Hubble image - which I realize was not taken to show off
the nucleus per se - it was taken to resolve the rest of the galaxy.
But you just look at this thing with MIRI and that nucleus just jumps
right out at you.
[Gaspar] Yeah, the accretion disk is quite bright at 5.6 microns.
[Ready] That's amazing.
And then you looks like you turn to point to the Galactic Center...
Three degrees offset from the Galactic Center, but close enough.
[Ready] Oh really, okay...
[Gaspar] You can see all the molecular clouds there.
[Ready] This is a stray light pointed model correlation.
What does that mean exactly?
[Gaspar] So during this observation set, this was not just the single image taken.
So a really high background one was taken here
and near the Galactic Center and they just wanted to measure
how different background lights actually enter.
[Ready] So what is next for MIRI...I mean, or I should say what is next for Team MIRI?
You have such a great group of people there and what do you all going to do?
Are you all going to be like, 'well, bye, we got MIRI commissioned
and now we're going to go off
and do our own things', or are you still working together?
[Gaspar] It's a fantastic group. And yes, many people
from the European Consortium have traveled back home already.
But ESA has quite a few people who are stationed at Space
Telescope and are going to continue to work on the project.
[Ready] Andras, thank you so much.
This is just amazing learning about MIRI and learning about what it was like to
go to the commissioning process and and just congratulations
to you and the whole MIRI team for just
bringing us this incredibly amazing instrument.
And really just this is what's taking Webb really deep into the infrared
as far...as as far as we can see, it's just it's just amazing work.
And thank you.
[Gaspar] Thank you so much for talking with me,
and I'm really happy to share because
I don't think many people understand why we needed six months
necessarily to get the telescope up and running, but
we needed to understand how everything works.
[Ready] It's a complex machine. [Gaspar] Thanks, it is,
yeah, thank you very much.
[Christian Ready] Thank you, Andras Gaspar, for telling us
about commissioning MIRI and a huge
thanks to my patrons for helping to keep Launch Pad Astronomy going.
And I'd like to welcome John Roberts as my newest supporter.
And if you'd like to join me
on this journey through this incredible universe of ours,
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Until next time, stay curious, my friend.