Spacewatch continues its full-time targeted astrometric follow-up of unnumbered near-Earth asteroids (NEAs) with the 1.8m (291) and 0.9m (691) telescopes on Kitt Peak in the Tohono O'odham Nation. As exclusive users of the 1.8m and 0.9m, we observe NEOs 24 nights per lunation, weather permitting. In bright time, we use the competitively allocated Steward Observatory Bok 2.3m telescope to reach NEAs with fainter magnitudes than possible with our telescopes. After Kitt Peak operations shut down in mid-March 2020, we received permission to operate our telescopes remotely on Oct 28, 2020. Permission to operate on site was granted in mid-May 2021.
Rapid follow-up is necessary before newly discovered NEAs' sky uncertainties grow too large and magnitudes grow too faint to detect. Our priorities are virtual impactors, MPC NEO Confirmation Page objects, Potentially Hazardous Asteroids, NEAs on the NEODyS-2 priority and faint object priority lists, NEAs observed by NEOWISE, potential planetary radar targets, potential spacecraft mission rendezvous targets, and candidates for the Yarkovsky Effect.
Spacewatch will present our lightcurve work conducted for the IAWN planetary defense campaign to observe Apophis during its 2021 close approach. This practice campaign treated Apophis as if it were unknown. With 6 nights of 1.8m data in January, we determined that Apophis’s rotation period is ~30.5 hours. As Apophis brightened, we observed 28 nights with the 0.9m and detected signs of tumbling. Adding our 0.9m data suppressed the 24-hour period alias feature in the periodogram constructed with data submitted by other lightcurve groups in the campaign.
We will provide an update on the design and construction of our new Cassegrain camera for use on the Bok 2.3m. It will increase the field-of-view (FOV) over that of our current Cassegrain imager thus allowing us to perform astrometric follow-up observations of NEAs with larger orbital uncertainties than our current camera does.
Over the past year, we have reviewed previous years' targeted astrometric data from the 1.8m to measure any NEAs that were missed. We also have improved our GUI targeting and analysis software programs.
Our collaboration continues with the Catalina Sky Survey and the University of Minnesota’s Minnesota Institute for Astrophysics to survey the sky for unknown faint NEOs using the Bok 2.3m telescope. We will report on the astrometric productivity of this survey and of Spacewatch’s use of the 1.8m, 0.9m, and 2.3m telescopes.