<p>The linked article is copied from a university <a href="https://www.ucf.edu/news/arecibo-observatory-returns-from-tropical-storm-isaias-lockdown-to-track-asteroid-for-nasa/" rel="noreferrer">press release</a>.
<a href="https://www.naic.edu/%7Epradar/press/2020NK1.php" rel="noreferrer">Arecibo's article</a> is more matter-of-fact but naturally also emphasizes the value of their own work.</p>
<p><a href="https://gssr.jpl.nasa.gov/" rel="noreferrer">NASA Goldstone</a> can do planetary radar and remains operational.
As <a href="https://echo.jpl.nasa.gov/introduction.html" rel="noreferrer">this page</a> says:</p>
<blockquote>
<p>Arecibo has twice the range and can see three times the volume of Goldstone,
while Goldstone, whose greater steerability provides twice the sky coverage and much longer tracking times, serves a complementary role.</p>
</blockquote>
<p>FAST has <a href="https://skyandtelescope.org/astronomy-blogs/astronomy-space-david-dickinson/fast-worlds-largest-radio-telescope-open/" rel="noreferrer">no transmitter</a> but presumably could take part in bistatic radar observations as <a href="https://skyandtelescope.org/astronomy-news/shedding-new-light-on-near-earth-asteroids-0804201544/" rel="noreferrer">GBT does</a>.</p>
<p>Radar can measure distance and radial velocity (<span class="math-container">$r$</span>, <span class="math-container">$\dot{r}$</span>) in a single observation, especially useful when combined with astrometry (<span class="math-container">$\alpha$</span>, <span class="math-container">$\delta$</span>) since the two different kinds of data are orthogonal.
Given enough observations over a long enough time, astronomers can determine asteroid orbits rather precisely through optical astrometry alone.</p>

CC BY-SA 4.0
2020-09-02T04:11:46.303Z
I found this interview with planetary scientist Edgard Rivera-Valentín [The Arecibo Telescope Is Damaged — And That's A Big Deal](https://www.npr.org/2020/08/26/906366009/the-arecibo-telescope-is-damaged-and-thats-a-big-deal) interesting as well.
uhoh
CC BY-SA 4.0
2020-11-20T02:52:19.170Z
I've added a new update to the question but I don't think it affects your answer at all.
uhoh
CC BY-SA 4.0
2020-08-24T15:02:10.693Z
2020-08-24T15:02:10.693Z
Mike G
<p><strong>update 3:</strong> <em>uhoh!</em></p>
<p><a href="https://i.sstatic.net/P7IJj.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/P7IJj.jpg" alt="Reddit's amateurradio/comments/k4stjr/aerial_shot_of_the_antenna_collapse_at_arecibo/" /></a></p>
<p>Source: <a href="https://www.reddit.com/r/amateurradio/comments/k4stjr/aerial_shot_of_the_antenna_collapse_at_arecibo/" rel="nofollow noreferrer">Reddit</a></p>
<p><strong>update 2:</strong> Sadly, parts of the dish have collapsed, several cables have snapped, and the Arecibo radio telescope is now decommissioned and demolition has been recommended because it is now too unsafe to do anything else.</p>
<ul>
<li><a href="https://www.nsf.gov/news/news_summ.jsp?cntn_id=301674" rel="nofollow noreferrer">NSF begins planning for decommissioning of Arecibo Observatory’s 305-meter telescope due to safety concerns</a></li>
<li><a href="https://www.nationalgeographic.com/science/2020/11/historic-radio-telescope-in-puerto-rico-to-be-demolished/" rel="nofollow noreferrer">Iconic radio telescope in Puerto Rico to be demolished</a></li>
</ul>
<p>related in Space SE: <a href="https://space.stackexchange.com/q/37533/12102">How many total hours had Arecibo transmitted a signal?
</a></p>
<p><strong>update 1:</strong> Science November 9, 2020: <a href="https://www.sciencemag.org/news/2020/11/second-cable-breaks-puerto-rico-s-arecibo-telescope" rel="nofollow noreferrer">Second cable breaks at Puerto Rico’s Arecibo telescope</a></p>
<hr />
<p>The NASA News item <a href="https://solarsystem.nasa.gov/news/1421/arecibo-observatory-returns-from-tropical-storm-isaias-lockdown-to-track-asteroid-for-nasa/" rel="nofollow noreferrer">Arecibo Observatory Returns from Tropical Storm Isaias Lockdown to Track Asteroid for NASA</a> begins:</p>
<blockquote>
<p>The National Science Foundation facility, managed by the University of Central Florida, determines that a newly discovered asteroid won’t threaten Earth</p>
</blockquote>
<p>Of course right after this there was a serious failure, a support cable for the focal plane instrumentation broke and seriously damaged the dish as well.</p>
<p>Are we currently at elevated risk to getting hit by an asteroid now that Arecibo can not help in making precise range-rate measurements of asteroids? Optical tracking provides detection and some orbit reconstruction, but the precise range and radial velocity measurements that can be done by radar can provide very precise data that can help distinguish an impact trajectory from one that will miss.</p>
<p>Could the <a href="https://en.wikipedia.org/wiki/Five-hundred-meter_Aperture_Spherical_Telescope" rel="nofollow noreferrer">Five-hundred-meter Aperture Spherical Telescope</a> fill in for Arecibo's role in asteroid astrometry?</p>

CC BY-SA 4.0
2020-08-24T02:18:21.960Z
It makes absolutely no difference. We currently have no means to deflect impactors. If they are gonna hit us, they will hit us.
Mick
CC BY-SA 4.0
2020-08-24T02:21:33.230Z
@Mick I absolutely disagree! This kind of data can tell you exactly where the impact will happen and when. This allows for planning. Examples: if it's in the ocean, it may be possible to move populations away from areas that can experience subsequent flooding. If it's on land, people can move. Disaster planning and relief agencies can consider issues of food distribution, etc.
uhoh
CC BY-SA 4.0
2020-08-24T02:57:10.373Z
I must admit that I'm sceptical, especially about the word "exactly". A prediction would have to be accurate enough (in time, location, trajectory and severity) for authorities to take effective action. Too wide an area or too severe an impact, and it becomes unmanageable. Too small an impact and it will just be ignored. I doubt if any nation on Earth has impactor/bolide contingency planning in place.
Mick
CC BY-SA 4.0
2020-08-24T07:57:17.960Z
The hazard is exactly the same as before, but the vulnerability is higher, so the risk as well (risk = hazard $\times$ vulnerability).
Jean-Marie Prival
CC BY-SA 4.0
2020-08-26T14:19:40.443Z
I suppose   "ZOMG we all gonna DIE" is not helping here :-)
Carl Witthoft
CC BY-SA 4.0
2020-12-02T09:20:54.120Z
Oh what a pity! I didn't even know that it collapsed! This makes me sad; it's Ellie's observatory from the film 'Contact'. And it could perhaps have discovered Planet IX. Hopefully they'll get it back usable again.
Greenhorn
<asteroids><astrometry><impact><impact-probability>
Are we less safe now that Arecibo is no more?
uhoh
# Are we less safe now that Arecibo is no more?

(Asked by: username_0 on 2020-08-24)

**update 3:** *uhoh!*

[![Reddit's amateurradio/comments/k4stjr/aerial_shot_of_the_antenna_collapse_at_arecibo/](https://i.sstatic.net/P7IJj.jpg)](https://i.sstatic.net/P7IJj.jpg)

Source: [Reddit](https://www.reddit.com/r/amateurradio/comments/k4stjr/aerial_shot_of_the_antenna_collapse_at_arecibo/)

**update 2:** Sadly, parts of the dish have collapsed, several cables have snapped, and the Arecibo radio telescope is now decommissioned and demolition has been recommended because it is now too unsafe to do anything else.

* [NSF begins planning for decommissioning of Arecibo Observatory’s 305-meter telescope due to safety concerns](https://www.nsf.gov/news/news_summ.jsp?cntn_id=301674)
* [Iconic radio telescope in Puerto Rico to be demolished](https://www.nationalgeographic.com/science/2020/11/historic-radio-telescope-in-puerto-rico-to-be-demolished/)

related in Space SE: [How many total hours had Arecibo transmitted a signal?](https://space.stackexchange.com/q/37533/12102)

**update 1:** Science November 9, 2020: [Second cable breaks at Puerto Rico’s Arecibo telescope](https://www.sciencemag.org/news/2020/11/second-cable-breaks-puerto-rico-s-arecibo-telescope)

---

The NASA News item [Arecibo Observatory Returns from Tropical Storm Isaias Lockdown to Track Asteroid for NASA](https://solarsystem.nasa.gov/news/1421/arecibo-observatory-returns-from-tropical-storm-isaias-lockdown-to-track-asteroid-for-nasa/) begins:

> The National Science Foundation facility, managed by the University of Central Florida, determines that a newly discovered asteroid won’t threaten Earth

Of course right after this there was a serious failure, a support cable for the focal plane instrumentation broke and seriously damaged the dish as well.

Are we currently at elevated risk to getting hit by an asteroid now that Arecibo can not help in making precise range-rate measurements of asteroids? Optical tracking provides detection and some orbit reconstruction, but the precise range and radial velocity measurements that can be done by radar can provide very precise data that can help distinguish an impact trajectory from one that will miss.

Could the [Five-hundred-meter Aperture Spherical Telescope](https://en.wikipedia.org/wiki/Five-hundred-meter_Aperture_Spherical_Telescope) fill in for Arecibo's role in asteroid astrometry?

**Tags:** asteroids, astrometry, impact, impact-probability
> **Comments:**
> **username_1**: It makes absolutely no difference. We currently have no means to deflect impactors. If they are gonna hit us, they will hit us.  
> **username_0**: @Mick I absolutely disagree! This kind of data can tell you exactly where the impact will happen and when. This allows for planning. Examples: if it's in the ocean, it may be possible to move populations away from areas that can experience subsequent flooding. If it's on land, people can move. Disaster planning and relief agencies can consider issues of food distribution, etc.  
> **username_1**: I must admit that I'm sceptical, especially about the word "exactly". A prediction would have to be accurate enough (in time, location, trajectory and severity) for authorities to take effective action. Too wide an area or too severe an impact, and it becomes unmanageable. Too small an impact and it will just be ignored. I doubt if any nation on Earth has impactor/bolide contingency planning in place.  
> **username_2**: The hazard is exactly the same as before, but the vulnerability is higher, so the risk as well (risk = hazard $\times$ vulnerability).  
> **username_3**: I suppose   "ZOMG we all gonna DIE" is not helping here :-)  
> **username_4**: Oh what a pity! I didn't even know that it collapsed! This makes me sad; it's Ellie's observatory from the film 'Contact'. And it could perhaps have discovered Planet IX. Hopefully they'll get it back usable again.  

---

## 1 answers

### Answer by username_5 on 2020-08-24. Score: 7 | Accepted answer

The linked article is copied from a university [press release](https://www.ucf.edu/news/arecibo-observatory-returns-from-tropical-storm-isaias-lockdown-to-track-asteroid-for-nasa/).
[Arecibo's article](https://www.naic.edu/%7Epradar/press/2020NK1.php) is more matter-of-fact but naturally also emphasizes the value of their own work.

[NASA Goldstone](https://gssr.jpl.nasa.gov/) can do planetary radar and remains operational.
As [this page](https://echo.jpl.nasa.gov/introduction.html) says:

> Arecibo has twice the range and can see three times the volume of Goldstone,
> while Goldstone, whose greater steerability provides twice the sky coverage and much longer tracking times, serves a complementary role.

FAST has [no transmitter](https://skyandtelescope.org/astronomy-blogs/astronomy-space-david-dickinson/fast-worlds-largest-radio-telescope-open/) but presumably could take part in bistatic radar observations as [GBT does](https://skyandtelescope.org/astronomy-news/shedding-new-light-on-near-earth-asteroids-0804201544/).

Radar can measure distance and radial velocity ($r$, $\dot{r}$) in a single observation, especially useful when combined with astrometry ($\alpha$, $\delta$) since the two different kinds of data are orthogonal.
Given enough observations over a long enough time, astronomers can determine asteroid orbits rather precisely through optical astrometry alone.

> **Comments:**
> **username_0**: I found this interview with planetary scientist Edgard Rivera-Valentín [The Arecibo Telescope Is Damaged — And That's A Big Deal](https://www.npr.org/2020/08/26/906366009/the-arecibo-telescope-is-damaged-and-thats-a-big-deal) interesting as well.  
> **username_0**: I've added a new update to the question but I don't think it affects your answer at all.  

---

