  We imaged Comet 252P/2000 G1 (LINEAR) (hereafter 252P) with the Hubble Space
Telescope and both 252P and P/2016 BA$_{14}$ (PanSTARRS) (hereafter BA$_{14}$)
with the Discovery Channel Telescope in March and April 2016, surrounding its
close encounter to Earth. The r'-band $Af\rho$ of 252P in a 0.2"-radius
aperture were $16.8\pm0.3$ and $57\pm1$ cm on March 14 and April 4,
respectively, and its gas production rates were: $Q$(OH) =
$(5.8\pm0.1)\times10^{27}$ s$^{-1}$, and $Q$(CN) = $(1.25\pm0.01)\times10^{25}$
s$^{-1}$ on April 17. The r'-band upper limit $Af\rho$ of BA1$_{14}$ was
$0.19\pm0.01$ cm in a 19.2"-radius aperture, and $Q$(CN) = $(1.4\pm0.1)10^{22}$
s$^{-1}$ on April 17, 2017. 252P shows a bright and narrow jet of a few hundred
kilometers long in the sunward direction, changing its projected position angle
in the sky with a periodicity consistent with 7.24 hours. However, its
photometric lightcurve is consistent with a periodicity of 5.41 hours. We
suggest that the nucleus of 252P is likely in a non-principal axis rotation.
The nucleus radius of 252P is estimated to be about $0.3\pm0.03$ km, indicating
an active fraction of 40% to >100% in its 2016 apparition. Evidence implies a
possible cloud of slow-moving grains surrounding the nucleus. The activity
level of 252P in the 2016 apparition increased by two orders of magnitude from
its previous apparitions, making this apparition unusual. On the other hand,
the activity level of BA14 appears to be at least three orders of magnitude
lower than that of 252P, despite its ten times or larger surface area.
