<p>These uncertainty plots are meant to aid observers trying to confirm Near Earth Object (NEO) candidates found by the surveys. Since the NEO surveys typically take 3-4 observations of a survey field over a short (~30 minutes) period of time, with a varying astrometric precision, a variety of potential orbits can be fit to these observations. A number (typically 2000 it seems) of variant orbits are fit to the same observations and the elements from these variant orbits are used to predict RA, Dec positions on the sky relative to the position predicted by the nominal orbit. This forms a cloud or line of points since the direction of motion is easier to constrain then the rate of motion (due to projection effects and the fact that the distance is hard to determine from short arcs) so a line of variations is formed. These variant orbits available from the NEO Confirmation Page (NEOCP) once you generate an ephemeris for one or more objects:
<a href="https://i.sstatic.net/G0FtL.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/G0FtL.png" alt="NEOCP showing link to the variant orbits and uncertainty maps" /></a></p>
<p>Clicking on that &quot;orbits&quot; link will provide the orbital elements on the nominal and variant orbits:
<a href="https://i.sstatic.net/QbXsT.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/QbXsT.png" alt="Variant orbits and orbital elements" /></a>
This particular object is moving fast, is close to Earth and has a very short arc so the uncertainty map is correspondingly large:
<a href="https://i.sstatic.net/AhtJl.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/AhtJl.png" alt="Uncertainty map for fast moving NEO candidate C813M2" /></a>
The declination uncertainty is ~200,000&quot; (55.5 degrees) so this would be a tough object to recover and confirm and you would need to observe many fields of view along this line of variations to be sure of recovering it.</p>
<p>These are color-coded based on the distance as described in the <a href="https://www.minorplanetcenter.net/iau/NEO/NEOCPNotes.html" rel="nofollow noreferrer">notes</a> (the link is easy to miss on the long <a href="https://www.minorplanetcenter.net/iau/NEO/toconfirm_tabular.html" rel="nofollow noreferrer">NEO Confirmation Page</a>):</p>
<blockquote>
<p>The uncertainty maps include an indication of objects that are close to the earth. Three colors are used to indicate objects at various distances:</p>
<ul>
<li>green, for objects that are more then 0.05 AU from the earth at the time used for the uncertainty map; these are further classified as follows:
<ul>
<li>dark blue, for orbits that are &quot;main-belt&quot;</li>
<li>magenta, for orbits that are Jupiter Trojans [this is not currently implemented, at the present time such orbits are colored dark blue]</li>
</ul>
</li>
<li>orange, for objects between 0.05 and 0.01 AU from the earth</li>
<li>red, for objects within 0.01 AU.</li>
</ul>
</blockquote>
<p>The uncertainty maps are an evolving function of time, observatory position and number of observations and the object will be removed from the NEOCP once confirmed, withdrawn (didn't exist or wasn't an asteroid) or lost. As an example, this is a candidate that has had 13 follow-up observations from other observatories (click &quot;observations&quot; link) over 2 days so the uncertainty in it's future position is much less smaller at ~2&quot;:
<a href="https://i.sstatic.net/azxwF.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/azxwF.png" alt="Much smaller uncertainty map for a NEO candidate that received follow-up" /></a></p>
<p>So in short, they are a way to visualize the current knowledge and uncertainty of where a NEO candidate will be in the future to aid observers who are deciding whether to try and observe and recover the object. If the uncertainty is small (few arcseconds), the object is not in need of further observations; consequently if the uncertainty is large and/or growing, it can aid in making the value call of spending the telescope time and how many fields of view of you telescope you might need to attempt to recover it.</p>

CC BY-SA 4.0
2022-09-22T00:33:14.707Z
2022-09-22T00:33:14.707Z
astrosnapper
<p>I am an observational astronomer. I have just started with the observations. If any of you use MinorPlanetCenter website to get the ephemeris of a possible NEO in the NEO confirmation page, there is an uncertainty map. I know how to read that but I am not sure how is it constructed, why are there about 2000 points in the map and what the color coding means.
I would be grateful if any of you can break it down for me.</p>
<p><a href="https://i.sstatic.net/OrRPr.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/OrRPr.png" alt="enter image description here" /></a></p>

CC BY-SA 4.0
2022-09-21T11:11:20.203Z
got a link to these graphs so that one can look at it in-situ than just a screenshot?
planetmaker
CC BY-SA 4.0
2022-09-22T05:28:03.987Z
@planetmaker The example appears to be from the [NEO Confirmation](https://minorplanetcenter.net/iau/NEO/toconfirm_tabular.html) page, whose contents change significantly from one day to the next.
Mike G
<observational-astronomy><telescope><asteroids>
The Interpretation of Uncertainty Map of NEO in Minor Planet Center page
unstableEquilibrium
# The Interpretation of Uncertainty Map of NEO in Minor Planet Center page

(Asked by: username_0 on 2022-09-21)

I am an observational astronomer. I have just started with the observations. If any of you use MinorPlanetCenter website to get the ephemeris of a possible NEO in the NEO confirmation page, there is an uncertainty map. I know how to read that but I am not sure how is it constructed, why are there about 2000 points in the map and what the color coding means.
I would be grateful if any of you can break it down for me.

[![enter image description here](https://i.sstatic.net/OrRPr.png)](https://i.sstatic.net/OrRPr.png)

**Tags:** observational-astronomy, telescope, asteroids
> **Comments:**
> **username_1**: got a link to these graphs so that one can look at it in-situ than just a screenshot?  
> **username_2**: @planetmaker The example appears to be from the [NEO Confirmation](https://minorplanetcenter.net/iau/NEO/toconfirm_tabular.html) page, whose contents change significantly from one day to the next.  

---

## 1 answers

### Answer by username_3 on 2022-09-22. Score: 3 | Accepted answer

These uncertainty plots are meant to aid observers trying to confirm Near Earth Object (NEO) candidates found by the surveys. Since the NEO surveys typically take 3-4 observations of a survey field over a short (~30 minutes) period of time, with a varying astrometric precision, a variety of potential orbits can be fit to these observations. A number (typically 2000 it seems) of variant orbits are fit to the same observations and the elements from these variant orbits are used to predict RA, Dec positions on the sky relative to the position predicted by the nominal orbit. This forms a cloud or line of points since the direction of motion is easier to constrain then the rate of motion (due to projection effects and the fact that the distance is hard to determine from short arcs) so a line of variations is formed. These variant orbits available from the NEO Confirmation Page (NEOCP) once you generate an ephemeris for one or more objects:
[![NEOCP showing link to the variant orbits and uncertainty maps](https://i.sstatic.net/G0FtL.png)](https://i.sstatic.net/G0FtL.png)

Clicking on that "orbits" link will provide the orbital elements on the nominal and variant orbits:
[![Variant orbits and orbital elements](https://i.sstatic.net/QbXsT.png)](https://i.sstatic.net/QbXsT.png)
This particular object is moving fast, is close to Earth and has a very short arc so the uncertainty map is correspondingly large:
[![Uncertainty map for fast moving NEO candidate C813M2](https://i.sstatic.net/AhtJl.png)](https://i.sstatic.net/AhtJl.png)
The declination uncertainty is ~200,000" (55.5 degrees) so this would be a tough object to recover and confirm and you would need to observe many fields of view along this line of variations to be sure of recovering it.

These are color-coded based on the distance as described in the [notes](https://www.minorplanetcenter.net/iau/NEO/NEOCPNotes.html) (the link is easy to miss on the long [NEO Confirmation Page](https://www.minorplanetcenter.net/iau/NEO/toconfirm_tabular.html)):

> The uncertainty maps include an indication of objects that are close to the earth. Three colors are used to indicate objects at various distances:
>
> * green, for objects that are more then 0.05 AU from the earth at the time used for the uncertainty map; these are further classified as follows:
>   + dark blue, for orbits that are "main-belt"
>   + magenta, for orbits that are Jupiter Trojans [this is not currently implemented, at the present time such orbits are colored dark blue]
> * orange, for objects between 0.05 and 0.01 AU from the earth
> * red, for objects within 0.01 AU.

The uncertainty maps are an evolving function of time, observatory position and number of observations and the object will be removed from the NEOCP once confirmed, withdrawn (didn't exist or wasn't an asteroid) or lost. As an example, this is a candidate that has had 13 follow-up observations from other observatories (click "observations" link) over 2 days so the uncertainty in it's future position is much less smaller at ~2":
[![Much smaller uncertainty map for a NEO candidate that received follow-up](https://i.sstatic.net/azxwF.png)](https://i.sstatic.net/azxwF.png)

So in short, they are a way to visualize the current knowledge and uncertainty of where a NEO candidate will be in the future to aid observers who are deciding whether to try and observe and recover the object. If the uncertainty is small (few arcseconds), the object is not in need of further observations; consequently if the uncertainty is large and/or growing, it can aid in making the value call of spending the telescope time and how many fields of view of you telescope you might need to attempt to recover it.


---

