Irregular moons of Saturn -- Greip For notes, see https://tilmanndenk.de/outersaturnianmoons/greip/#1 23 Oct 2018 / TD Overview Table Moon name Greip Saturn range 18e6 km Orbit period 2.6 years Orbit direction retrograde Size ~ 5 km Rotation period 12 45 hh:mm Discovery year 2006 (A) Designations and discovery circumstances (A1) Moon name Greip (A2) Moon abbrev. (TD) Gre (A3) IAU number Saturn LI (A4) Provisional designation S/2006 S 4 (A5) SPICE ID 651 (A6) Also-used label S51 (A7) First observation date 05 Jan 2006 (A7) Announcement date 30 Jun 2006 (A7) IAU circular announcement no. 8727 (A8) Discoverers Sheppard S. et al. (B) Orbit parameters (B1) Orbit direction retrograde (B2) Group member Norse (B3) Dynamical family Hyrrokkin/Greip? Suttungr? (B4) Periapsis range 12.65e6 km (B5) Semi-major axis 18.46e6 km (B6) Apoapsis range 24.27e6 km (B7) Semi-major axis 306 R_Saturn (B8) Semi-major axis 0.123 au (B9) Semi-major axis 0.28 R_Hill (B10) Orbit eccentricity 0.32 (B11) Orbit inclination 174.8 ° (B12) Inclination supplemental angle 5.2 ° (B13) Orbital period 936 d (B14) Orbital period 2 6 3.25 y:m:w (B15) Mean orbit velocity 1.43 km/s (C) Physical parameters (C1) Mean size ~ 5 -0.75 +1.25 km (C2) Mean radius ~ 2.3 km (C3) Equatorial circumference ~ 15 km (C4) Minimum equatorial axes ratio 1.18 (C5) Axes radii (a x b x c) ~ unknown (C5) (C6) Mass ~ 3e13 kg (C7) Mean density (?) 0.5 g/cm^3 (C8) Surface escape velocity ~ 3 km/h (C9) Rotation period 12.75 h (C9) Rotation period error 0.35 h (C9) Spin rate 1.88 d^(-1) (C10) Spin direction unknown (C11) Seasons unknown (C12) Pole direction (ecliptic longitude λ) unknown (C12) Pole direction (ecliptic latitude β) unknown (C13) Pole direction (geocentric RA) unknown (C13) Pole direction (geocentric Dec) unknown (C14) Absolute visual magnitude ~ 15.4 mag (C15) Apparent visual magnitude from Earth 24.4 mag (C16) Best apparent magnitude for Cassini 15.4 mag (C17) Spectral slope unknown (C17) B-R color index unknown (C18) Albedo (?) 0.06 (C19) Hill sphere radius ~ 310 km (C20) Hill sphere radius ~ 135 r_Gre