Orbit Determination and Nongravitational Effect Characterization for Emirates Mission Targets (10253) Westerwald and (13294) Rockox

Abstract

Detecting the Yarkovsky effect on kilometer-scale main-belt asteroids remains challenging, yet it directly affects impact-hazard assessment and spacecraft navigation. Ahead of the Emirates Mission to the Asteroid Belt (EMA) flybys of (10253) Westerwald (2030) and (13294) Rockox (2031), we determine precise orbits for both targets by combining 52 yr of ground-based astrometry, debiased against Gaia DR2, with Gaia Focused Product Release (FPR) along-scan measurements (43 and 44 transits, respectively), weighted directly by their per-transit covariance matrices and corrected for the Lommel–Seeliger photocenter offset. The six-parameter solutions reach Gaia along-scan normalized residuals of 1.08 and 1.36, constrain both targets to subkilometer formal position uncertainties at the solution epoch, and yield 3σ flyby position uncertainties of 7.00 and 5.06 km, an astrometric basis for EMA encounter planning. Introducing a transverse acceleration in seven-parameter fits yields no reliable Yarkovsky detection; Westerwald gives signal-to-noise ratio (S/N) = 0.87, consistent with noise, and Rockox gives S/N = 2.65, below the detection threshold, with an S-ratio of 11.94 far above the physical-plausibility limit. Thus, even with milliarcsecond-level Gaia FPR astrometry, the Yarkovsky signal of these main-belt asteroids remains below the detection limit over multidecadal ground-based arcs; routine detection will require the longer baseline and improved calibration of the forthcoming Gaia DR4.