  The XO project's first objective is to find hot Jupiters transiting bright
stars, i.e. V < 12, by precision differential photometry. Two XO cameras have
been operating since September 2003 on the 10,000-foot Haleakala summit on
Maui. Each XO camera consists of a 200-mm f/1.8 lens coupled to a 1024x1024
pixel, thinned CCD operated by drift scanning. In its first year of routine
operation, XO has observed 6.6% of the sky, within six 7 deg-wide strips
scanned from 0 deg to +63 deg of declination and centered at RA=0, 4, 8, 12,
16, and 20 hours. Autonomously operating, XO records 1 billion pixels per clear
night, calibrates them photometrically and astrometrically, performs aperture
photometry, archives the pixel data and transmits the photometric data to STScI
for further analysis. From the first year of operation, the resulting database
consists of photometry of 100,000 stars at more than 1000 epochs per star with
differential photometric precision better than 1% per epoch. Analysis of the
light curves of those stars produces transiting-planet candidates requiring
detailed follow up, described elsewhere, culminating in spectroscopy to measure
radial-velocity variation in order to differentiate genuine planets from the
more numerous impostors, primarily eclipsing binary and multiple stars.
