<p>In 2018, the US Congress passed a bill to allocate budgets and mission goals to NASA.</p>
<p><a href="https://www.congress.gov/115/bills/hr5503/BILLS-115hr5503rh.pdf" rel="nofollow noreferrer">Section 321</a> of that Bill mentions a goal for detection of NEOs of diameter &gt;140 Km. Quote:</p>
<blockquote>
<p>(1) The George E. Brown, Jr. Near-Earth Object Survey Act (Public Law 109–155) established the Near-Earth Object Survey program to detect, track, and catalogue the physical characteristics of near-Earth objects equal to or greater than 140 meters in diameter in order to assess the threat of such objects to Earth.</p>
</blockquote>
<blockquote>
<p>(2) The goal of the Survey program is to achieve 90 percent completion of the near-Earth project catalogue (based on statistically predicted populations of near-Earth objects) not later than 15 years after the date of the enactment of the George E. Brown, Jr. Near-Earth Object Survey Act.</p>
</blockquote>
<p>I am interested in knowing (and possibly understanding) the methodology used to arrive at the &quot;statistically predicted population(s)&quot;, without which Congress's goal (90% of the population) is a moving target.</p>
<p>Subsidiary: Is this methodology accepted by astronomers worldwide?</p>
<ul>
<li>EDIT1:</li>
</ul>
<p>I am aware of the statistical technique called <a href="https://en.wikipedia.org/wiki/Mark_and_recapture" rel="nofollow noreferrer">&quot;Mark &amp; Recapture&quot;</a>, often used in wildlife studies. But I have doubts that it can be used for estimating the size of NEOs (of d=140m+). Asteroids do not &quot;mix&quot; back randomly in the population as fish would do in a pond.</p>

CC BY-SA 4.0
2021-07-20T14:08:06.180Z
@uhoh, you misunderstood. I was talking about the number. Congress said they wanted 90% of X to be catalogued by 2033 (2018+15). So, there is an agreed X. What is the methodology to get to that X.
Ng Ph
CC BY-SA 4.0
2021-07-20T14:11:20.530Z
oh, *that* size!
uhoh
CC BY-SA 4.0
2021-07-20T14:48:09.710Z
@uhoh, made the edit to clarify that's the size of the population. Note that the Bill also mentioned that only 30% of that overall population (d>140m) have been catalogued in 2018, in comparison to 90% of the population of (d>1Km).
Ng Ph
CC BY-SA 4.0
2021-07-22T20:57:49.023Z
Just a guess, but I'd say they inferred a probability distribution (probably something like Rosin-Rammler, often used for particle size distribution) from the bigger diameters, and extrapolated this distribution to estimate the population of smaller diameters.
Jean-Marie Prival
CC BY-SA 4.0
2021-07-23T07:58:12.620Z
@Jean-Marie Prival, that's another interesting approach. I guess the difficulty is to convince that the extrapolation to a larger population is justified. More or less the same statistical issue as "Tag & Recapture". We now have two candidate approaches. Progress!
Ng Ph
<earth><near-earth-object><nasa>
How does NASA estimate the size of the population of Near-Earth Objects (NEO) of diameter>140 meters?
Ng Ph
# How does NASA estimate the size of the population of Near-Earth Objects (NEO) of diameter>140 meters?

(Asked by: username_0 on 2021-07-19)

In 2018, the US Congress passed a bill to allocate budgets and mission goals to NASA.

[Section 321](https://www.congress.gov/115/bills/hr5503/BILLS-115hr5503rh.pdf) of that Bill mentions a goal for detection of NEOs of diameter >140 Km. Quote:

> (1) The George E. Brown, Jr. Near-Earth Object Survey Act (Public Law 109–155) established the Near-Earth Object Survey program to detect, track, and catalogue the physical characteristics of near-Earth objects equal to or greater than 140 meters in diameter in order to assess the threat of such objects to Earth.

> (2) The goal of the Survey program is to achieve 90 percent completion of the near-Earth project catalogue (based on statistically predicted populations of near-Earth objects) not later than 15 years after the date of the enactment of the George E. Brown, Jr. Near-Earth Object Survey Act.

I am interested in knowing (and possibly understanding) the methodology used to arrive at the "statistically predicted population(s)", without which Congress's goal (90% of the population) is a moving target.

Subsidiary: Is this methodology accepted by astronomers worldwide?

* EDIT1:

I am aware of the statistical technique called ["Mark & Recapture"](https://en.wikipedia.org/wiki/Mark_and_recapture), often used in wildlife studies. But I have doubts that it can be used for estimating the size of NEOs (of d=140m+). Asteroids do not "mix" back randomly in the population as fish would do in a pond.

**Tags:** earth, near-earth-object, nasa

> **Comments:**
> **username_0**: @username_1, you misunderstood. I was talking about the number. Congress said they wanted 90% of X to be catalogued by 2033 (2018+15). So, there is an agreed X. What is the methodology to get to that X.  
> **username_1**: oh, *that* size!  
> **username_0**: @username_1, made the edit to clarify that's the size of the population. Note that the Bill also mentioned that only 30% of that overall population (d>140m) have been catalogued in 2018, in comparison to 90% of the population of (d>1Km).  
> **username_2**: Just a guess, but I'd say they inferred a probability distribution (probably something like Rosin-Rammler, often used for particle size distribution) from the bigger diameters, and extrapolated this distribution to estimate the population of smaller diameters.  
> **username_0**: @username_2, that's another interesting approach. I guess the difficulty is to convince that the extrapolation to a larger population is justified. More or less the same statistical issue as "Tag & Recapture". We now have two candidate approaches. Progress!  

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## 0 answers

