  The speckle interferometry program at the the 4.1 m Southern Astrophysical
Research Telescope (SOAR), started in 2008, now accumulated over 30,300
individual observations of 12,700 distinct targets. Its main goal is to monitor
orbital motion of close binaries, including members of high-order hierarchies
and low-mass dwarfs in the solar neighborhood. The results from 2021 are
published here, totaling 2,623 measurements of 2,123 resolved pairs and
non-resolutions of 763 targets. The median measured separation is 0.21", and 75
pairs were closer than 30 mas. The calibration of scale and orientation is
based on the observations of 103 wide pairs with well-modeled motion. These
calibrators are compared to the latest Gaia data release, and minor (0.5%)
systematic errors were rectified, resulting in accurate relative positions with
typical errors on the order of 1 mas. Using these new measurements, orbits of
282 binaries are determined here (54 first determinations and 228 corrections).
We resolved for the first time 50 new pairs, including subsystems in known
binaries. A list of 94 likely spurious pairs unresolved at SOAR (mostly close
Hipparcos binaries) is also given.
