  One-opposition near-Earth asteroids (NEAs) are growing in number, and they
must be recovered to prevent loss and mismatch risk, and to improve their
orbits, as they are likely to be too faint for detection in shallow surveys at
future apparitions. We aimed to recover more than half of the one-opposition
NEAs recommended for observations by the Minor Planet Center (MPC) using the
Isaac Newton Telescope (INT) in soft-override mode and some fractions of
available D-nights. During about 130 hours in total between 2013 and 2016, we
targeted 368 NEAs, among which 56 potentially hazardous asteroids (PHAs),
observing 437 INT Wide Field Camera (WFC) fields and recovering 280 NEAs (76%
of all targets). Engaging a core team of about ten students and amateurs, we
used the THELI, Astrometrica, and the Find_Orb software to identify all moving
objects using the blink and track-and-stack method for the faintest targets and
plotting the positional uncertainty ellipse from NEODyS. Most targets and
recovered objects had apparent magnitudes centered around V~22.8 mag, with some
becoming as faint as V~24 mag. One hundred and three objects (representing 28%
of all targets) were recovered by EURONEAR alone by Aug 2017. Orbital arcs were
prolonged typically from a few weeks to a few years; our oldest recoveries
reach 16 years. The O-C residuals for our 1,854 NEA astrometric positions show
that most measurements cluster closely around the origin. In addition to the
recovered NEAs, 22,000 positions of about 3,500 known minor planets and another
10,000 observations of about 1,500 unknown objects (mostly main-belt objects)
were promptly reported to the MPC by our team. Four new NEAs were discovered
serendipitously in the analyzed fields, increasing the counting to nine NEAs
discovered by the EURONEAR in 2014 and 2015.
