We describe a major survey of the Milky Way halo designed to test for kinematic substructure caused by destruction of accreted satellites .
We use the Washington photometric system to identify halo stars efficiently for spectroscopic followup .
Tracers include halo giants ( detectable out to more than 100 kpc ) , blue horizontal branch stars , halo stars near the main sequence turnoff , and the “ blue metal-poor stars ” of Preston et al .
( 79 ) .
We demonstrate the success of our survey by showing spectra of stars we have identified in all these categories , including giants as distant as 75 kpc .
We discuss the problem of identifying the most distant halo giants .
In particular , extremely metal-poor halo K dwarfs are present in approximately equal numbers to the distant giants for V > 18 , and we show that our method will distinguish reliably between these two groups of metal-poor stars .

We plan to survey 100 square degrees at high galactic latitude , and expect to increase the numbers of known halo giants , BHB stars and turnoff stars by more than an order of magnitude .
In addition to the strong test that this large sample will provide for the question “ was the Milky Way halo accreted from satellite galaxies ? ” , we will improve the accuracy of mass measurements of the Milky Way beyond 50 kpc via the kinematics of the many distant giants and BHB stars we will find .

We show that one of our first datasets constrains the halo density law over galactocentric radii of 5–20 kpc and z heights of 2–15 kpc .
The data support a flattened power-law halo with b/a of 0.6 and exponent –3.0 .
More complex models with a varying axial ratio may be needed with a larger dataset .