The debiased absolute-magnitude and orbit distributions as well as source regions for near-Earth objects ( NEOs ) provide a fundamental frame of reference for studies of individual NEOs and more complex population-level questions .
We present a new four-dimensional model of the NEO population that describes debiased steady-state distributions of semimajor axis , eccentricity , inclination , and absolute magnitude H in the range 17 < H < 25 .
The modeling approach improves upon the methodology originally developed by in that it is , for example , based on more realistic orbit distributions and uses source-specific absolute-magnitude distributions that allow for a power-law slope that varies with H .
We divide the main asteroid belt into six different entrance routes or regions ( ER ) to the NEO region : the \nu _ { 6 } , 3:1J , 5:2J and 2:1J resonance complexes as well as Hungarias and Phocaeas .
In addition we include the Jupiter-family comets as the primary cometary source of NEOs .
We calibrate the model against NEO detections by Catalina Sky Surveys ’ stations 703 and G96 during 2005–2012 , and utilize the complementary nature of these two systems to quantify the systematic uncertainties associated to the resulting model .
We find that the ( fitted ) H distributions have significant differences , although most of them show a minimum power-law slope at H \sim 20 .
As a consequence of the differences between the ER-specific H distributions we find significant variations in , for example , the NEO orbit distribution , average lifetime , and the relative contribution of different ERs as a function of H .
The most important ERs are the \nu _ { 6 } and 3:1J resonance complexes with JFCs contributing a few percent of NEOs on average .
A significant contribution from the Hungaria group leads to notable changes compared to the predictions by Bottke et al .
in , for example , the orbit distribution and average lifetime of NEOs .
We predict that there are 962 ^ { +52 } _ { -56 } ( 802 ^ { +48 } _ { -42 } \times 10 ^ { 3 } ) NEOs with H < 17.75 ( H < 25 ) and these numbers are in agreement with the most recent estimates found in the literature ( the uncertainty estimates only account for the random component ) .
Based on our model we find that relative shares between different NEO groups ( Amor , Apollo , Aten , Atira , Vatira ) are ( 39.4,54.4,3.5,1.2,0.3 ) % , respectively , for the considered H range and that these ratios have a negligible dependence on H .
Finally , we find an agreement between our estimate for the rate of Earth impacts by NEOs and recent estimates in the literature , but there remains a potentially significant discrepancy in the frequency of Tunguska-sized and Chelyabinsk-sized impacts .