On February 11 2022, James Webb Space Telescope released this image to test its mirrors:

enter image description here

Is JWST the first telescope to release test images before its first light?


1 Answer 1


Publishing 'test' images is common.

However, 'first light' is generally defined as the first time the optical train is used to resolve an image. First Light is always going to be a test image. You may be thinking of 'first science images' instead of 'first light'.

Here is the first light image from Hubble (right) compared to a ground telescope:

Hubble First Light


Notice how fuzzy it was. This was before the mission to repair the spherical aberration in the mirror.

And here is the first light 'test' image from WISE, the Wide-field Survey Infrared Explorer space telescope:

WISE First Light

image credit: NASA/JPL-Caltech/UCLA

And not to leave out the ESA, here's the 'First Light' image of galaxy M51 from the Herschel space observatory, compared to the Spitzer space telescope image of the same target:

Herschel first light

All of these are 'test' images pre-calibration.

  • $\begingroup$ Good point - I have changed the first sentence. $\endgroup$
    – Dan Hanson
    Commented Jun 14, 2022 at 17:22

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