  K2 was a community-driven NASA mission where all targets were proposed
through guest observer programs. Among those, the K2 Galactic Archaeology
Program (K2GAP) was devoted to measuring asteroseismic signals from giant stars
to inform studies of the Galaxy, with about 25% of the observed K2 targets
being allocated to this program. Here, we provide an overview of this program.
We discuss in detail the target selection procedure and provide a python code
that implements the selection function, see https://github.com/sanjibs/k2gap .
Additionally, we discuss the detection completeness of the asteroseismic
parameters $\nu_{\rm max}$ and $\Delta \nu$. Broadly speaking, the targets were
selected based on 2MASS color $J-Ks > 0.5$, with finely tuned adjustments for
each campaign. Making use of the selection function we compare the observed
distribution of asteroseismic masses to theoretical predictions. The median
asteroseismic mass is higher by about 4% compared to predictions. Additionally,
the number of seismic detections is on average 14% lower than expected. We
provide a selection-function-matched mock catalog of stars based on a synthetic
model of the Galaxy for the community to be used in subsequent analyses of the
K2GAP data set, see http://www.physics.usyd.edu.au/k2gap .
