<p>[rewritten to address the revised question]</p>

<p>Maybe, depending on how fussy you want to be about "resolved".</p>

<p><a href="https://ui.adsabs.harvard.edu/abs/1995Icar..113..353N/abstract" rel="nofollow noreferrer">This</a> is a study from 1995, using observations of asteroid 4179 Toutatis made in 1992 with <em>HST</em>. They reported marginal resolution of the asteroid, as suggested by this figure comparing a deconvolved image of a star (observed with the same filter and imager location) and a similarly deconvolved image of the asteroid itself (each pixel corresponds to about 450 m at the distance of the asteroid):</p>

<p><a href="https://i.sstatic.net/Mt32U.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/Mt32U.jpg" alt="Figure 4 from Noll et al. 1995"></a></p>

<p>The appearance of the asteroid is pretty clearly <em>not</em> a point source, but it's also fair to say it's only partly resolved, and mostly just in one direction.</p>

<p>(My admittedly vague impression is that this is one of the best, if not <em>the</em> best, case of <em>HST</em> "resolving" a near-Earth asteroid.)</p>

<p>Most observations of near-Earth objects with <em>HST</em> are, I think, aimed at getting optical information on compositions not possible from other wavelengths, and sometimes refining estimates of rotation rates, as was done this year (using data from 2012) for the asteroid <a href="https://arxiv.org/abs/1903.00096" rel="nofollow noreferrer">Bennu</a>, currently being visited by OSIRIS-REx.</p>

<p>In practice, you get <em>much</em> better spatial resolution <a href="https://echo.jpl.nasa.gov" rel="nofollow noreferrer">using radar</a> (including line-of-sight distance variations due to the structure of the asteroids from time-of-return measurements, allowing you to construct 3D models of them), so there's not much point in trying to resolve them with <em>HST</em>.</p>

CC BY-SA 4.0
2019-06-25T09:55:17.257Z
In order to support your "Yes" I think it would be good to find *at least once instance* of something that is spatially resolved, even if it turns out to only be a few pixels. The first reference is [paywalled](https://www.sciencedirect.com/science/article/abs/pii/S0019103585710275?via%3Dihub) so I won't be able to check it this week; the second does not seem to have anything resolved (no images are shown in the paper).
uhoh
CC BY-SA 4.0
2019-06-25T10:07:41.930Z
The first reference does say in its abstract: "Toutatis was marginally resolved by the HST. There is evidence for an extended object with a projected illuminated dimension less than 2.8 km while the best fit symmetric model has a maximum illuminated size of 2.0 km and deconvolutions suggest an irregular object with a maximum dimension of 1.7 km"
Peter Erwin
CC BY-SA 4.0
2019-06-25T10:09:06.690Z
(Somewhat pedantically, I would argue that if you observing something with one of *HST*'s cameras -- as opposed to one of its spectrographs -- you are "imaging" it...)
Peter Erwin
CC BY-SA 4.0
2019-06-25T10:15:01.407Z
The title of the 1995 paper *is* "Imaging of Asteroid 4179 Toutatis with the Hubble Space Telescope"....
Peter Erwin
CC BY-SA 4.0
2019-06-25T10:17:18.657Z
Being published in Icarus means that the paper has likely passed substantial peer-review scrutiny, but language like "There is evidence for an extended object..." sounds somewhat equivocated and I find it only *mildly convincing*. I think it will be better to have a little more information about the results so we can be convinced ourselves though. I'd like to be able to balance the evidence for with the evidence *against*, and the abstract alone doesn't provide an opportunity to do that.
uhoh
CC BY-SA 4.0
2019-06-25T10:47:26.563Z
Noll et at 1995 is mentioned in [New Insights of Asteroid 4179 Toutatis Using China Chang'e-2 Close Flyby Optical Measurements](https://iopscience.iop.org/article/10.1088/0004-6256/149/1/21/meta) (not paywalled, yay!) in passing, perhaps someone with access to it will be kind enough to grab an image or a bit of explanation of the data and edit it in to your answer.
uhoh
CC BY-SA 4.0
2019-06-25T08:58:13.640Z
2019-06-30T13:38:32.980Z
2019-06-30T13:38:32.980Z
Peter Erwin
<p><a href="https://astronomy.stackexchange.com/a/14676/7982">This answer to <em>How big will Apophis appear?</em></a> points out that the near Earth asteroid Apophis will likely be close to 2 arcseconds in diameter as seen from Earth during its close approach in 2029. I speculate that if the Hubble Space Telescope were still operational then, it could potentially image the asteroid in visible light at a few dozen pixels in diameter.</p>
<p>This leads me to wonder if the Hubble has ever been used to image<sup>†</sup> or at least spatially resolve in some way an asteroid during a close pass to the Earth before.</p>
<p><sup>†</sup>Here the verb &quot;image&quot; should be taken to mean the act of producing a resolved image of an object so that different pixels correspond to intensity from different parts of the body being imaged. For the purposes of this question please don't consider telescope images in which an asteroid happens to appear but is too far away to be resolved. Thanks!</p>

<asteroids><hubble-telescope><near-earth-object>
Has Hubble ever been used to try to image a near Earth asteroid?
uhoh
# Has Hubble ever been used to try to image a near Earth asteroid?

(Asked by: username_0 on 2019-06-23)

[This answer to *How big will Apophis appear?*](https://astronomy.stackexchange.com/a/14676/7982) points out that the near Earth asteroid Apophis will likely be close to 2 arcseconds in diameter as seen from Earth during its close approach in 2029. I speculate that if the Hubble Space Telescope were still operational then, it could potentially image the asteroid in visible light at a few dozen pixels in diameter.

This leads me to wonder if the Hubble has ever been used to image† or at least spatially resolve in some way an asteroid during a close pass to the Earth before.

†Here the verb "image" should be taken to mean the act of producing a resolved image of an object so that different pixels correspond to intensity from different parts of the body being imaged. For the purposes of this question please don't consider telescope images in which an asteroid happens to appear but is too far away to be resolved. Thanks!

**Tags:** asteroids, hubble-telescope, near-earth-object


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## 1 answers

### Answer by username_1 on 2019-06-25. Score: 6 | Accepted answer

[rewritten to address the revised question]

Maybe, depending on how fussy you want to be about "resolved".

[This](https://ui.adsabs.harvard.edu/abs/1995Icar..113..353N/abstract) is a study from 1995, using observations of asteroid 4179 Toutatis made in 1992 with *HST*. They reported marginal resolution of the asteroid, as suggested by this figure comparing a deconvolved image of a star (observed with the same filter and imager location) and a similarly deconvolved image of the asteroid itself (each pixel corresponds to about 450 m at the distance of the asteroid):

[![Figure 4 from Noll et al. 1995](https://i.sstatic.net/Mt32U.jpg)](https://i.sstatic.net/Mt32U.jpg)

The appearance of the asteroid is pretty clearly *not* a point source, but it's also fair to say it's only partly resolved, and mostly just in one direction.

(My admittedly vague impression is that this is one of the best, if not *the* best, case of *HST* "resolving" a near-Earth asteroid.)

Most observations of near-Earth objects with *HST* are, I think, aimed at getting optical information on compositions not possible from other wavelengths, and sometimes refining estimates of rotation rates, as was done this year (using data from 2012) for the asteroid [Bennu](https://arxiv.org/abs/1903.00096), currently being visited by OSIRIS-REx.

In practice, you get *much* better spatial resolution [using radar](https://echo.jpl.nasa.gov) (including line-of-sight distance variations due to the structure of the asteroids from time-of-return measurements, allowing you to construct 3D models of them), so there's not much point in trying to resolve them with *HST*.

> **Comments:**
> **username_0**: In order to support your "Yes" I think it would be good to find *at least once instance* of something that is spatially resolved, even if it turns out to only be a few pixels. The first reference is [paywalled](https://www.sciencedirect.com/science/article/abs/pii/S0019103585710275?via%3Dihub) so I won't be able to check it this week; the second does not seem to have anything resolved (no images are shown in the paper).  
> **username_1**: The first reference does say in its abstract: "Toutatis was marginally resolved by the HST. There is evidence for an extended object with a projected illuminated dimension less than 2.8 km while the best fit symmetric model has a maximum illuminated size of 2.0 km and deconvolutions suggest an irregular object with a maximum dimension of 1.7 km"  
> **username_1**: (Somewhat pedantically, I would argue that if you observing something with one of *HST*'s cameras -- as opposed to one of its spectrographs -- you are "imaging" it...)  
> **username_1**: The title of the 1995 paper *is* "Imaging of Asteroid 4179 Toutatis with the Hubble Space Telescope"....  
> **username_0**: Being published in Icarus means that the paper has likely passed substantial peer-review scrutiny, but language like "There is evidence for an extended object..." sounds somewhat equivocated and I find it only *mildly convincing*. I think it will be better to have a little more information about the results so we can be convinced ourselves though. I'd like to be able to balance the evidence for with the evidence *against*, and the abstract alone doesn't provide an opportunity to do that.  
> **username_0**: Noll et at 1995 is mentioned in [New Insights of Asteroid 4179 Toutatis Using China Chang'e-2 Close Flyby Optical Measurements](https://iopscience.iop.org/article/10.1088/0004-6256/149/1/21/meta) (not paywalled, yay!) in passing, perhaps someone with access to it will be kind enough to grab an image or a bit of explanation of the data and edit it in to your answer.  

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