We present analysis of the asteroid surface density distribution of main belt asteroids ( mean perihelion \Delta \simeq 2.404 AU ) in five ecliptic latitude fields , -17 \raisebox { -2.58 pt } { $ \stackrel { \raisebox { -0.86 pt } { $ \textstyle > $ } } { \sim } $% } \beta ( \arcdeg ) \raisebox { -2.58 pt } { $ \stackrel { \raisebox { -0.86 pt } { $ \textstyle < % $ } } { \sim } $ } +15 , derived from deep Large Binocular Telescope ( LBT ) V - band ( 85 % completeness limit V = 21.3 mag ) and Spitzer Space Telescope IRAC 8.0 µm ( 80 % completeness limit \sim 103 ~ { } \mu Jy ) fields enabling us to probe the 0.5–1.0 km diameter asteroid population .
We discovered 58 new asteroids in the optical survey as well as 41 new bodies in the Spitzer fields .
The derived power law slopes of the number of asteroids per square degree are similar within each \sim 5 ° ecliptic latitude bin with a mean value of -0.111 \pm 0.077 .
For the 23 known asteroids detected in all four IRAC channels mean albedos range from 0.24 \pm 0.07 to 0.10 \pm 0.05 .
No low albedo asteroids ( p _ { V } \stackrel { \raisebox { -0.86 pt } { $ \textstyle < $ } } { \sim } 0.1 ) were detected in the Spitzer FLS fields , whereas in the SWIRE fields they are frequent .
The SWIRE data clearly samples asteroids in the middle and outer belts providing the first estimates of these km-sized asteroids ’ albedos .
Our observed asteroid number densities at optical wavelengths are generally consistent with those derived from the Standard Asteroid Model within the ecliptic plane .
However , we find an over density at \beta \raisebox { -2.58 pt } { $ \stackrel { \raisebox { -0.86 pt } { $ \textstyle > $ } } { \sim } % $ } 5 ° in our optical fields , while the infrared number densities are under dense by factors of 2 to 3 at all ecliptic latitudes .