  We present J, H and K photometry of the Orion Nebula Cluster obtained at the
CTIO/Blanco 4 m telescope in Cerro Tololo with the ISPI imager. From the
observations we have assembled a catalog of about 7800 sources distributed over
an area of approximately 30'x40', the largest of any survey deeper than 2MASS
in this region. The catalog provides absolute coordinates accurate to about
0.15 arcseconds and 3sigma photometry in the 2MASS system down to J 19.5mag, H
18.0mag, K 18.5mag, enough to detect planetary size objects 1 Myr old under Av
10mag of extinction at the distance of the Orion Nebula. We present a
preliminary analysis of the catalog, done comparing the (J-H, H-K) color-color
diagram, the (H, J-H) and (K, H-K) color-magnitude diagrams and the JHK
luminosity functions of three regions at increasing projected distance from the
Trapezium. Sources in the inner region typically show IR colors compatible with
reddened T Tauri stars, whereas the outer fields are dominated by field stars
seen through an amount of extinction which decreases with the distance from the
center. The color-magnitude diagrams make it possible to clearly distinguish
between the main ONC population, spread across the full field, and background
sources. The luminosity functions of the inner region, corrected for
completeness, remain relatively flat in the sub-stellar regime regardless of
the strategy adopted to remove background contamination.
