New precise positions in 2013–2019 and a catalog of ground-based astrometric observations of 11 Neptunian satellites (1847–2019) based on Gaia-DR2

Abstract

Context. Developing high-precision ephemerides for Neptunian satellites requires not only the continuation of observing campaigns but also the collection and improvement of existing observations. So far, no complete catalogs of observations of Neptunian satellites are available. Aims. We aim to provide new, precise positions, and to compile a catalog including all available ground-based astrometric observations of Neptunian satellites. The observations are tabulated in a single and consistent format and given in the same timescale, the Terrestrial Time (TT), and reference system, the International Celestial Reference System (ICRS), including necessary changes and corrections. Methods. New CCD observations of Triton and Nereid were made at Lijiang 2.4-m and Yaoan 0.8-m telescopes in 2013–2019, and then reduced based on Gaia-DR2. Furthermore, a catalog called OCNS2019 (Observational Catalog of Neptunian Satellites (2019 version)) was compiled, after recognizing and correcting errors and omissions. Furthermore, in addition to what was considered for the COSS08 catalog for eight main Saturnian satellites, all observed absolute and relative coordinates were converted to the ICRS with corrections for star catalog biases with respect to Gaia-DR2. New debiasing tables for both the modern and old star catalogs, which were previously not provided based on Gaia-DR2, are developed and applied. Treatment of missing positions of comparison bodies in conversions of observed relative coordinates are proposed. Results. OCNS2019 and the new debiasing tables are publicly available online. OCNS2019 includes 24996 observed coordinates of 11 Neptunian satellites obtained over 3741 nights from 1847 to 2019. All observations are given in TT and ICRS. The star catalog biases are removed, which are significant for Nereid and outer satellites. We obtained 880 (5% of total now available) new coordinates for Triton over 41 nights (1% of total observation nights so far), and 790 (14%) for Nereid over 47 nights (10%). The dispersions of these new positions are about 0.″03 for Triton and 0.″06 for Nereid. Conclusions. OCNS2019 should be useful in improving ephemerides for the above-mentioned objects.

Antarctic Survey Telescope 3-3: Overview, System Performance and Preliminary Observations at Yaoan, Yunnan

“…The Yaoan station has excellent logistics for supporting the long-term commissioning of telescopes. AST3-3 collaborates with YaoAn High Precision Telescope (YAHPT hereafter, [44]) for multiband follow-up observations of detected transient sources.…”

The orbits of Triton and Nereid and the pole orientation of Neptune from Voyager,HubbleSpace Telescope, and Earth-based astrometry in 1847–2020

“…The Earth-based astrometric data of Triton and Nereid include all those in OCNS2019 4 (Yuan et al 2021) and one year of new CCD observations obtained from the Yaoan 0.8-m telescope (IAU code O49) in 2019-2020. These data, as well as the HST astrometry described in Sect.…”

“…the same as that of Yuan et al (2021). These observations include 1492 new Earth-based observed coordinates (7% of the total available) obtained over 61 nights (2% of total observation nights) for Triton, and 378 (6%) over 28 nights (6%) for Nereid.…”

“…On the one hand, the observations include a lot of new accurate Earth-based positions reduced with the Gaia astrometic catalogs (Lindegren et al 2016(Lindegren et al , 2018 along with accurate positions obtained from Hubble Space Telescope (HST) (Showalter et al 2019). The corrections of numerous old observations applied in OCNS2019 (Yuan et al 2021), as well as new Triton and Nereid astrometric positions (presented in Sect. 2.3), are also included.…”

The Astrometric Performance Test of 80-cm Telescope at Yaoan Station and Precise CCD Positions of Apophis

“…The 80-cm azimuthal-mounting telescope at Yaoan Station, Purple Mountain Observatory has served for precise astrometry since it was set up in the year of 2018. Although some precise positions by the telescope have been published (Yuan et al 2021, the performance of the telescope has not been specified. The potentiality of the telescope should be taped through the performance test, which may serve for some survey or occultation observation.…”