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

Section 321 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", 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.

  • 1
    $\begingroup$ @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. $\endgroup$
    – Ng Ph
    Commented Jul 20, 2021 at 14:08
  • $\begingroup$ oh, that size! $\endgroup$
    – uhoh
    Commented Jul 20, 2021 at 14:11
  • 1
    $\begingroup$ @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). $\endgroup$
    – Ng Ph
    Commented Jul 20, 2021 at 14:48
  • $\begingroup$ 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. $\endgroup$ Commented Jul 22, 2021 at 20:57
  • $\begingroup$ @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! $\endgroup$
    – Ng Ph
    Commented Jul 23, 2021 at 7:58


You must log in to answer this question.

Browse other questions tagged .