(163899) 2003 SD220

(163899) 2003 SD₂₂₀
	Radar image of 2003 SD220 from Arecibo Observatory on 16 December 2018
Discovery
Discovered by	LONEOS
Discovery site	Anderson Mesa Stn.
Discovery date	29 September 2003
Designations
MPC designation	(163899) 2003 SD220
Alternative designations	2003 SD220 · 2000 AD229
Minor planet category	NEO · PHA · Aten
Orbital characteristics
	Epoch 4 September 2017 (JD 2458000.5)
	Uncertainty parameter 0
Observation arc	15.96 yr (5,828 days)
Aphelion	1.0019 AU
Perihelion	0.6533 AU
Semi-major axis	0.8276 AU
Eccentricity	0.2106
Orbital period (sidereal)	0.75 yr (275 days)
Mean anomaly	322.67°
Mean motion	1° 18m 33.12s / day
Inclination	8.4591°
Longitude of ascending node	274.05°
Argument of perihelion	326.47°
Earth MOID	0.0174 AU · 6.8 LD
Physical characteristics
Mean diameter	0.80±0.02 km; 1.03 km (calculated)
Synodic rotation period	285±5 h; 11.9±0.2 days
Geometric albedo	0.20 (assumed); 0.31±0.04
Spectral type	S (assumed)
Apparent magnitude	13.5 (2021 peak)
Absolute magnitude (H)	17.3 · 17.36

(163899) 2003 SD₂₂₀ is a sub-kilometer asteroid and tumbling slow rotator, classified as near-Earth object and potentially hazardous asteroid of the Aten group, which orbit the Sun between Venus and Earth. Its orbital period of 0.75 years means that it orbits the Sun about 4 times for every 3 of the Earth. It was discovered on 29 September 2003, by astronomers of the Lowell Observatory Near-Earth-Object Search at Anderson Mesa Station near Flagstaff, Arizona.^[2]

Earth flybys 2015–2027

It passed about 28 lunar distances (LD) from the Earth on 25 December 2015. It came within about 7 LD (0.0189 AU) on 22 December 2018. Its peak brightness was about 13.13 magnitude on 16 December 2018.

Observations are planned for favorable flybys in 2021, 2024, and 2027. It passed with 14 LD (0.0363 AU) on 17 December 2021, and 34 LD (0.0884 AU) on 2 December 2024, and 54 LD (0.1382 AU) on 12 November 2027.^[1]

Patrick Taylor of Arecibo Observatory suggested it could be a target for a future robotic mission.^[6]

Close approach^[1]
Date	JPL SBDB nominal geocentric distance	uncertainty region (3-sigma)
2021-12-17	5427633 km	± 22 km

2015

It was observed in December 2015 at a distance of 28.3 lunar distances (0.07296 AU) on 24 December, and its brightest was 15.22 magnitude on 16 December. It showed an elongated shape, up to 2 km wide, described as being shaped like a sweet potato.^{[citation needed]}

GDSCC		Arecibo Observatory
17 December 2015	22 December 2015	3–16 December 2015

Path of asteroid during December 2015 (3 day motion)

Closest flyby 2018

2003 SD₂₂₀ passed its closest distance of 7.34 LD (0.01899 AU) on 22 December 2018. It was on the list of Goldstone targets for December 2018 ^[7] to gain more information for the Near-Earth Object Human Space Flight Accessible Targets Study (NHATS).^[8]

Asteroid 2003 SD₂₂₀ radar images (15–17 December 2018)^[9]

Its peak brightness was about 13.1 magnitude on 16 December 2018, moving south from Ursa Major and Boötes into Ophiuchus at closest approach and into Sagittarius.

The daily motion of *(163899) 2003 SD220* in December 2018

2021

2003 SD₂₂₀ passed at a distance of 14.1 lunar distances (0.03628 AU) on 17 December 2021. It was observed by the Goldstone Solar System Radar from November to December 2021.

22 November 2021

Notes

^ Lightcurve plot of (163899) 2003 SD₂₂₀, by Brian Warner, Palmer Divide Station, California (2015). Rotation period of 285±5 hours with a brightness amplitude of 2.2±0.1 mag. Quality Code 2+. Summary figures at the LCDB