A Near-Earth Asteroid Population Estimate from the LINEAR Survey
Abstract
I estimate the size and shape of the near-Earth asteroid (NEA) population using survey data from the Lincoln Near-Earth Asteroid Research (LINEAR) project, covering 375,000 square degrees of sky and including more than 1300 NEA detections. A simulation of detection probabilities for different values of orbital parameters and sizes combined with the detection statistics in a Bayesian framework provides a correction for observational bias and yields the NEA population distribution as a function of absolute magnitude, semi-major axis, eccentricity, and inclination. The NEA population is more highly inclined than previously estimated, and the total number of kilometer-sized NEAs is 1227−90 +170 (1σ).
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REFERENCES AND NOTES
1
The term near-Earth asteroids (NEAs) refers to asteroids with perihelia less than 1.3 AU, and aphelia greater 0.983 AU. This definition does not include objects with observable cometary comas or tails, although cataloged asteroids may include extinct comet nuclei.
2
Bottke W. F., Jedike R., Morbidelli A., Petit J., Gladman B., Science 288, 2190 (2000).
3
W. F. Bottke et al., Icarus, in press.
4
Rabinowitz D., Helin E., Lawrence K., Pravdo S., Nature 403, 165 (2000).
5
Stokes G., Evans J., Viggh H., Shelly F., Pearce E., Icarus 148, 21 (2000).
6
The LINEAR detection algorithm images each telescope field five times per night at half-hour intervals. Thus, 500,000 square degrees of coverage represents 2.5 million square degrees of imaging.
7
The integration times in this survey were selected to allow the system to cover 600 fields (about 1200 square degrees) while filling up the time available during the night. In winter, this allows for 11-s integration times, whereas in summer, as little as 3 s.
8
The a-e-i-H parameter space is broken into bins that are 0.1 AU wide in semi-major axis, 0.1 wide in eccentricity, 5° wide in inclination, and 0.5 magnitudes wide in absolute magnitude. For the plot in Fig. 3, the semi-major axis dimension was converted to bins 0.2 AU wide. The ranges of the parameters are 0.6 to 3.6 AU in semi-major axis, 0 to 1 in eccentricity, 0 to 50° in inclination, and 11 to 23 magnitudes in absolute magnitude. Bins with a-e values that do not meet the definition of NEA (1) are excluded.
9
The arguments of perihelion and the longitudes of the ascending node are assigned by a pseudo-random number generator producing a uniform distribution from 0° to 360°. The mean anomalies are evenly spaced from 0° to 360° at intervals of 0.5°.
10
I use the convention that absolute magnitude H = 18 corresponds to a diameter of 1 km. Absolute magnitude is the apparent brightness an object would have if placed at a theoretical position 1 AU from Earth and 1 AU from the Sun, with a Sun-asteroid-Earth phase angle of zero degrees. The correspondence of H = 18 with a diameter of 1 km is equivalent to using an albedo of 0.11, a widely assumed average value.
11
E. M. Shoemaker, R. F. Wolfe, C.S. Shoemaker, Geol. Soc. Am. Spec. Paper 247 (1990), pp. 155–170.
12
E. J. Öpik, Proc. R. Irish Acad.54A,165 (1951).
13
Sponsored by the Department of the Air Force and NASA under Air Force Contract F19628-00-C-0002. Opinions, interpretations, conclusions, and recommendations are those of the author and are not necessarily endorsed by the United States Air Force. The author acknowledges financial support from the Lincoln Scholars Program at MIT Lincoln Laboratory. The author wishes to thank R. Binzel for guidance, F. Shelly and the telescope operators for collecting the data used in this analysis, and P. Hopman and R. Sayer for technical advice.
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Published In
Science
Volume 294 | Issue 5547
23 November 2001
23 November 2001
Submission history
Received: 13 August 2001
Accepted: 12 October 2001
Published in print: 23 November 2001
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- Joseph Scott Stuart
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