Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The population of natural Earth satellites   We have for the first time calculated the population characteristics of the
Earth's irregular natural satellites (NES) that are temporarily captured from
the near-Earth-object (NEO) population. The steady-state NES size-frequency and
residence-time distributions were determined under the dynamical influence of
all the massive bodies in the solar system (but mainly the Sun, Earth, and
Moon) for NEOs of negligible mass. To this end, we compute the NES capture
probability from the NEO population as a function of the latter's heliocentric
orbital elements and combine those results with the current best estimates for
the NEO size-frequency and orbital distribution. At any given time there should
be at least one NES of 1-meter diameter orbiting the Earth. The average
temporarily-captured orbiter (TCO; an object that makes at least one revolution
around the Earth in a co-rotating coordinate system) completes
$(2.88\pm0.82)\rev$ around the Earth during a capture event that lasts
$(286\pm18)\days$. We find a small preference for capture events starting in
either January or July. Our results are consistent with the single known
natural TCO, 2006 RH$_{120}$, a few-meter diameter object that was captured for
about a year starting in June 2006. We estimate that about 0.1% of all meteors
impacting the Earth were TCOs.

24
The categories of this paper are: dg-ga
8
The categories of this paper are: hep-ex
1
The categories of this paper are: cs
18
The categories of this paper are: econ
5
The categories of this paper are: gr-qc
23
The categories of this paper are: solv-int
25
The categories of this paper are: patt-sol
37
The categories of this paper are: supr-con
31
The categories of this paper are: ao-sci
13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
27
The categories of this paper are: comp-gas
0
The categories of this paper are: hep-ph
9
The categories of this paper are: nlin
14
The categories of this paper are: math-ph
3
The categories of this paper are: physics