The orbit of Nereid based on observations

Abstract

Ephemerides of natural satellites are needed to carry out space missions to planets and to study the dynamics of Solar system bodies. Continuous observations of planetary satellites allow new, more accurate ephemerides to be derived. In this paper a new model of the motion of the Neptunian satellite Nereid is developed. The model is based on all published (736) and unpublished (140) ground‐based observations and 72 observations made by the Voyager spacecraft in 1989. The root‐mean‐square (rms) deviations of the observed satellite coordinates from their theoretical values are equal to 0.30 and 0.32 arcsec in right ascension and declination, respectively. The main contributors to these deviations are early ground‐based observations of Nereid. Estimations of the precision of the ephemeris of Nereid made by our original method show that the errors of the ephemeris do not exceed 0.03 arcsec (1σ) up to 2020. Comparing our ephemeris of Nereid with the Jet Propulsion Laboratory (JPL) results, the discrepancies do not exceed 0.04 arcsec in right ascension and declination over the 1980–2011 time period. A new ephemeris of Nereid is proposed via the MULTI‐SAT ephemeris facility.

Orbits of the Irregular Satellites of Uranus and Neptune

“…We note that the overall uncertainty envelope grows in time. Nereid's plane-of-sky uncertainty is ∼50 mas by 2030, similar to the Emelyanov & Arlot (2011) estimates with the bootstrap and Monte Carlo methods. In the Uranus system, Margaret and Ferdinand would benefit from more observations, while in the Neptune system, Psamathe and Neso, with their respective orbital periods of 25 and 26 yr, have the greatest need for follow-up.…”

“…Nereid has a variety of position measurements, from the historic measurements of van Biesbroeck (1951) and van Biesbroeck (1957) that reported relative positions of Nereid with respect to Neptune, to (i.e., van Biesbroeck 1951(i.e., van Biesbroeck , 1957Veiga et al 1999) in order to reduce the effects of systematic errors in observations. Emelyanov & Arlot (2011) noticed the same issue with the older measurements and used the mean value of the residuals as a bias. We decided to refrain from using any type of biases specific for ground-based observations in the current fit.…”

“…Some of the most precise measurements (< 70 mas) were obtained by Yu et al (2018) and Yu et al (2019) because they were reduced with respect to the GAIA star catalog. Other sources of recent astrometry were Emelyanov & Arlot (2011), 140 data points from 2000 to 2010, and Gomes-Júnior et al (2015), 873 data points from 1992 to 2014.…”

“…Jacobson (2009) updated that previous orbital solution based on additional data. Emelyanov & Arlot (2011) developed an independent dynamical model for Nereid and made the ephemeris available on the MULTI-SAT ephemerides computation facility (Emelyanov & Arlot 2008). Most recently, Tang et al (2021) reported on ephemeris development for Nereid that included some high-precision GAIA catalog reduced astrometry.…”

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

“…To support current and future scientific investigations of the Neptune system and relevant space exploration missions (e.g., NASA's Trident, Mitchell et al 2019;Prockter et al 2013), high-precision ephemerides for Neptunian satellites are needed (Jacobson 2009;Brozović et al 2011Brozović et al , 2020Emelyanov & Arlot 2011;Jacobson et al 2012;Emelyanov & Samorodov 2015). The precision of ephemerides and determined dynamical parameters depends both on the precision of observations and on the length of the time interval covered by observations (Desmars et al 2009a;Emelyanov 2010;Jacobson et al 2012;Arlot et al 2012;Emelyanov & Samorodov 2015;Lainey 2016).…”