Asteroids

1620 Geographos help

Last update: 2026-08-03 16:33 UTC

Orbital Properties

Epoch

61200.0

MJD

Orbit type

Apollo

Perihelion (q)

0.828

Aphelion (Q)

1.664

Eccentricity (e)

0.336

Inclination (i)

13.3

deg

Orbit period (P)

507.9

Earth MOID

0.02953

U parameter

0.0

Next Earth close approach

Date

2026-08-12

Nominal distance (from Earth center)

0.17044

25497019

Maximum Brightness

14.4

mag

Risk

Object is not in risk list

Physical Properties

Absolute Magnitude (H)

15.2

mag

Diameter

5000 | 2000 | 1500

Taxonomic type

Rotation period (T)

5.223

Discovery Information

Discovery Date

1951-09-14

Observatory

Palomar Mountain

ORBIT VISUALISATION TOOLS

External links

Proper elements

Epoch

Near present day

Near middle of observation arc

Orbit properties

Epoch
Semimajor Axis
Eccentricity (e)
Inclination (i)
Long. of Ascending Node (Ω)
Arg. of Perihelion (ω)
Mean Anomaly (M)
Perihelion distance
Aphelion distance
Asc. Node-Earth Sep.
Desc. Node-Earth Sep.
MOID
Orbit Period
U parameter

Value

1-sigma variation

Unit

Epoch

Value

61200.0000

1-sigma variation

Unit

MJD

Semimajor Axis

Value

1.245804

1-sigma variation

1.323E-10

Unit

Eccentricity (e)

Value

0.335518

1-sigma variation

9.478E-9

Unit

Inclination (i)

Value

13.3368

1-sigma variation

2.019E-6

Unit

Long. of Ascending Node (Ω)

Value

337.1349

1-sigma variation

2.476E-6

Unit

Arg. of Perihelion (ω)

Value

277.0291

1-sigma variation

3.116E-6

Unit

Mean Anomaly (M)

Value

354.67949

1-sigma variation

2.836E-6

Unit

Perihelion distance

Value

0.827814

1-sigma variation

Unit

Aphelion distance

Value

1.663793

1-sigma variation

Unit

Asc. Node-Earth Sep.

Value

0.051844

1-sigma variation

Unit

Desc. Node-Earth Sep.

Value

0.163019

1-sigma variation

Unit

MOID

Value

0.029531

1-sigma variation

Unit

Orbit Period

Value

507.8937

1-sigma variation

Unit

U parameter

Value

0.0

1-sigma variation

Unit

Covariance Matrix

	a	e	i	Ω	ω	M
a	1.74982E-20	-8.39286E-19	-8.67550E-17	-8.75790E-17	2.18659E-16	-3.29695E-16
e	-8.39286E-19	8.98285E-17	1.16919E-15	8.80674E-15	-2.31625E-14	1.79283E-14
i	-8.67550E-17	1.16919E-15	4.07803E-12	-1.47931E-12	1.23029E-12	3.22967E-13
Ω	-8.75790E-17	8.80674E-15	-1.47931E-12	6.13128E-12	-6.65166E-12	2.08123E-12
ω	2.18659E-16	-2.31625E-14	1.23029E-12	-6.65166E-12	9.71202E-12	-5.20545E-12
M	-3.29695E-16	1.79283E-14	3.22967E-13	2.08123E-12	-5.20545E-12	8.04503E-12

Date of computation: 2026-08-03 16:33 UTC

Note: The ASCII file is in a format suitable for Orbfit input.

Download ASCII file:

Physical properties

Rotation Period
Quality
Amplitude
Rotation Direction
Spinvector L
Spinvector B

Rotational properties

Value

Unit

Source

Rotation Period

Value

5.223

5.220

5.223

Unit

Source

[10]

[1]

[3]

[4]

[2]

Quality

Value

Unit

Source

[10]

Amplitude

Value

1.91

1.13

1.91

1.22

1.1-2.03

Unit

mag

Source

[3]

[1]

[4]

[2]

[10]

Rotation Direction

Value

RETRO

Unit

Source

[-]

[5]

[-]

Spinvector L

Value

Unit

Source

[1]

Spinvector B

Value

Unit

Source

[1]

Taxonomy
Taxonomy (all)

Taxonomy

Value

Unit

Source

Taxonomy

Value

Unit

Source

[6]

[7]

Taxonomy (all)

Value

Unit

Source

[8]

[9]

Absolute Magnitude (H)
Slope Parameter (G)

H / G

Value

Unit

Source

Absolute Magnitude (H)

Value

15.216

16.5

Unit

mag

Source

[11]

[12]

Slope Parameter (G)

Value

0.15**

Unit

Source

[11]

Albedo
Diameter

Size and albedo

Value

Unit

Source

Albedo

Value

0.19

Unit

Source

[14]

Diameter

Value

5000 | 2000 | 1500

Unit

Source

[13]

Color Index Information

Color Index Information

Value

Unit

Source

Color Index Information

Value

0.89

0.5

0.46

Unit

B-V

U-B

V-R

Source

[15]

[16]

[15]

Sightings

Sightings

Value

Unit

Source

Sightings

Value

Visual S

Radar R

Unit

Source

[17]

[18]

Download this part as:

Sources

No.	Name	Additional
[1]	EARN	1.) Lowell Observatory Near-Earth Asteroid Photometric Survey (NEAPS): Paper 3. Skiff, Brian A et al.
[2]	EARN	1.) Near-Earth Asteroid Lightcurve Analysis at the Center for Solar System Studies: 2019 January-April, B.D. Warner
[3]	EARN	1.) Near-Earth Asteroid Lightcurve Analysis at the Center for Solar System Studies: 2019 July-September, B.D. Warner
[4]	EARN	1.) Near-Earth Asteroid Lightcurve Analysis at the Center for Solar System Studies: 2019 September-2020 January, B.D. Warner
[5]	EARN	1.) Kaasalainen, M. et al. (2001) Icarus 153, 37-51. (Optimization Methods for Asteroid Lightcurve Inversion) 2.) Kwiatkowski, T. (1995) Astron. & Astrophys. 294, 274-277. (Sideral period, pole and shape of asteroid 1620 Geograhos)
[6]	EARN	1.) DeMeo, F.E. et al. (2014) Icarus 227, 112-122. (Mars encounters cause fresh surfaces on some near-Earth asteroids) (contains taxonomic classification of 249 NEAs)
[7]	EARN	1.) Michaël Marsset et al 2022 AJ 163 165
[8]	EARN	1.) Tholen, D.J. (1989) in "Asteroids II" (Eds. R.P.Binzel et al.), Univ.Ariz.Press, Tucson, USA, pp. 1139-1150. 2.) Hicks, M.D. et al. (1998) Icarus 133, 69-78. (The Unusual Spectra of 15 Near-Earth Asteroids and Extinct Comet Candidates)(1566,1620,2063,2102,2201,3200,4953,6053,6489, 7092,8176,1994ES1,1995CR,1996JA1) 3.) Bus, S.J. & Binzel, R.P. (2002) Icarus 158,106-145. (Phase II of the Small Main-Belt Asteroid Spectrographic Survey: A Feature-Based Taxonomy.) 4.) Binzel, R.P. et al. (2004) Icarus 170, 259-294. (Observed spectral properties of near-Earth objects: results for population distribution, source regions, and space weathering processes.) 5.) DeMeo, F.E. et al. (2014) Icarus 227, 112-122. (Mars encounters cause fresh surfaces on some near-Earth asteroids) (contains taxonomic classification of 249 NEAs)
[9]	EARN	Earth Asteroids Research Node: https://earn.dlr.de
[10]	EARN	1.) Magnusson, P. et al. (1996) Icarus 123, 227-244. (Photometric Observations and Modeling of Asteroid 1620 Geographos) 2.) Krugly, Yu. N. et al. (2002) Proceedings of ACM2002, ESA-SP500, pp. 903-906. (CCD photometry of Near-Earth asteroids in 2001) (rot.per. for 719,1916,26760,33342 2001 MF1; LCs for 1620,3103,5587,1999 KW4) 3.) Dunlap, J.L. (1974) Astron. J. 79, 324-332. (Minor planets and related objects. XV. Asteroid (1620) Geographos) 4.) Weidenschilling, S.J. et al. (1990) Icarus 86, 402-447. (Photometric geodesy of main-belt asteroids. III - Additional lightcurves)(.1620..) 5.) Michalowski, T. et al. (1994) Acta Astron. 44, 223-226. (CCD photometry of asteroid 1620) 6.) Kwiatkowski, T. (1995) Astron. & Astrophys. 294, 274-277. (Sideral period, pole and shape of asteroid 1620 Geograhos) 7.) Prokofeva, V.V. et al. (1997) Pis'ma Astronomicheskii Zhurnal 23, 870-880; Engl. Trans. Astron. Lett. 23, 758-767. (1620) 8.) Harris, A.W. (DLR) (1998) Icarus 131, 291-301. (A Thermal Model for Near-Earth Asteroids) 9.) Karachkina, L.G. (1998) Astron. Vestn. 32, 327-339; Engl. Trans. Solar System Res. 32, 287-289. (Modulation of brightness of asteroid 1620 Geographos) 10.) Hudson, R. S. & S. J. Ostro. (1999) Icarus 140, 369-378. (Physical model of asteroid 1620 Geographos from radar and optical data.) 11.) Kaasalainen, M. et al. (2001) Icarus 153, 37-51. (Optimization Methods for Asteroid Lightcurve Inversion) 12.) Krugly, Yu. N. et al. (2002) Proceedings of ACM2002, ESA-SP500, pp. 903-906. (CCD photometry of Near-Earth asteroids in 2001) (rot.per. for 719,1916,26760,33342 2001 MF1; LCs for 1620,3103,5587,1999 KW4) 13.) Durech, J. et al. (2008) Astron. Astrophys. 489, L25-L28. (Detection of the YORP effect in asteroid (1620) Geographos) 14.) Ye, Q. et al. (2009) MPB 36, 126. (CCD LIGHTCURVE ANALYSIS OF (53430) 1999 TY16) 15.) Skiff, B.A. et al. (2012) MPB 39, 111-130. (LOWELL OBSERVATORY NEAR-EARTH ASTEROID PHOTOMETRIC SURVEY (NEAPS) - 2008 MAY THROUGH 2008 DECEMBER) (46 NEAs) 16.) Warner, B.D. (2016) MPB 43, 143-154. (NEAR-EARTH ASTEROID LIGHTCURVE ANALYSIS AT CS3-PALMER DIVIDE STATION: 2015 OCTOBER-DECEMBER)(36NEAs)
[11]	ESA Aegis	ESA orbit determination and impact monitoring system
[12]	EARN	1.) Magnusson, P. et al. (1996) Icarus 123, 227-244. (Photometric Observations and Modeling of Asteroid 1620 Geographos)
[13]	EARN	1.) Veeder, G.J. et al. (1989) Astron. J. 97, 1211-1219. (Radiometry of near-earth asteroids) 2.) Nugent, C.R. et al. (2015) Astrophys. J. 814_117 (13pp) (NEOWISE Reactivation Mission Year One: Preliminary Asteroid Diameters and Albedos)(201 NEOs) 3.) Nugent, C.R. et al. (2016) Astron. J. 152_63 (12pp) (NEOWISE Reactivation Mission Year Two: Asteroid Diameters and Albedos) (207 NEOs) 4.) Tedesco, E.F. et al. (2004) IRAS Minor Planet Survey. IRAS-A-FPA-3-RDR-IMPS-V6.0. NASA Planetary Data System.
[14]	EARN	1.) Ostro, S.J. et al. (1996) Icarus 121, 46-66. (Radar Observations of Asteroid 1620 Geographos) 2.) Veeder, G.J. et al. (1989) Astron. J. 97, 1211-1219. (Radiometry of near-earth asteroids) 3.) Nugent, C.R. et al. (2015) Astrophys. J. 814_117 (13pp) (NEOWISE Reactivation Mission Year One: Preliminary Asteroid Diameters and Albedos)(201 NEOs) 4.) Nugent, C.R. et al. (2016) Astron. J. 152_63 (12pp) (NEOWISE Reactivation Mission Year Two: Asteroid Diameters and Albedos) (207 NEOs) 5.) Tedesco, E.F. et al. (2004) IRAS Minor Planet Survey. IRAS-A-FPA-3-RDR-IMPS-V6.0. NASA Planetary Data System.
[15]	EARN	1.) Dandy, C.L.; Fitzsimmons, A.; Collander-Brown, S.J. (2003) Icarus 163, 363-373. (Optical colors of 56 near-Earth objects: trends with size and orbit)
[16]	EARN	1.) Tedesco, E.F. (1989) in "Asteroids II" (Eds. R.P.Binzel et al.), Univ.Ariz.Press, Tucson, USA, pp. 1090-1138.
[17]	EARN	1.) Bus, S.J. & Binzel, R.P. (2002) Icarus 158,106-145. (Phase II of the Small Main-Belt Asteroid Spectrographic Survey: A Feature-Based Taxonomy.) 2.) Hicks, M.D. et al. (1995) Icarus 113, 456-459. (Rotationally resolved spectra of 1620 Geographos) 3.) Binzel, R.P. et al. (2004) Icarus 170, 259-294. (Observed spectral properties of near-Earth objects: results for population distribution, source regions, and space weathering processes.) 4.) Hicks, M.D. et al. (1998) Icarus 133, 69-78. (The Unusual Spectra of 15 Near-Earth Asteroids and Extinct Comet Candidates)(1566,1620,2063,2102,2201,3200,4953,6053,6489, 7092,8176,1994ES1,1995CR,1996JA1) 5.) Fevig. R.A. and U. Fink (2007) Icarus 188, 175-188. (Spectral observations of 19 weathered and 23 fresh NEAs and their correlations with orbital parameters)(433,1036, 1627,1685,1862,1866,1943,1980,3103,3122,3199,3671,4183,4341, 4954,5587,5751,5836,6037,7358,7482,7753,7822,7977,8201, 10563,11066,13651,13651,19356,20236,20255,35107,85490, J97GD32,J97UH9,J97US9,J98HE3,J98HT31,J98ME3,J98MS2,K04LC2) 6.) Sanchez, J.A. et al. (2012) Icarus 220, 36-50. (Phase reddening on near-Earth asteroids: Implications for mineralogical analysis, space weathering and taxonomic classification) (1036,1620,1627,1862,1980,4179,4954,6239, 11398,25143,35107,66146)
[18]	EARN	1.) Hudson, R.S. & S.J. Ostro (1997) B.A.A.S 29, 966. (Recent Radar Modeling Results: 1620 Geographos and 4179 Toutatis) 2.) Ostro, S.J. et al. (1995) Nature 375, 474. (Extreme elongation of asteroid 1620 geographos from radar images) 3.) Ostro, S.J. et al. (1996) Icarus 121, 46-66. (Radar Observations of Asteroid 1620 Geographos) 4.) Ostro, S.J. et al. (1991) Astron. J. 102, 1490-1502. (Asteroid radar astrometry) 5.) Hudson, R. S. & S. J. Ostro. (1999) Icarus 140, 369-378. (Physical model of asteroid 1620 Geographos from radar and optical data.)

Observational Information

Arc Length
Unobserved
Normalized RMS of residuals

Arc Information

Value

Unit

Source

Arc Length

Value

27366

Unit

Source

[1]

Unobserved

Value

Unit

Source

[1]

Normalized RMS of residuals

Value

0.405075

Unit

Source

[1]

Astrometry Summary

First Observation
Last Observation
Total Optical Observations (Discarded)

Optical

Value

Unit

Source

First Observation

Value

1951-08-31.45556

Unit

Source

[2]

Last Observation

Value

2026-08-03.181307

Unit

Source

[2]

Total Optical Observations (Discarded)

Value

9560 (91)

Unit

Source

[1]

Radar Summary

First Observation
Last Observation
Delay (Discarded)
Doppler (Discarded)
Total Optical Observations (Discarded)

Radar

Value

Unit

Source

First Observation

Value

1983-02-27

Unit

Source

[3]

Last Observation

Value

1994-09-02

Unit

Source

[3]

Delay (Discarded)

Value

3 (0)

Unit

Source

[1]

Doppler (Discarded)

Value

4 (0)

Unit

Source

[1]

Total Radar Observations (Discarded)

Value

7 (0)

Unit

Source

[1]

Note: The ASCII file is in a format suitable for Orbfit input.

Sources

No.	Name	Additional
[1]	ESA Aegis	ESA orbit determination and impact monitoring system
[2]	MPC	Minor Planet Center: https://www.minorplanetcenter.net
[3]	JPL Radar Observations	Jet Propulsion Laboratory: https://ssd.jpl.nasa.gov/dat/radar_data_ast.txt

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Note: Ephemerides requests are limited to a maximum of 1000 points and a final date not exceeding 2040/12/31 00:00.

Close Approaches for 1620 Geographos from 1950 to 2126

Body	Date in UTC	Time uncert. in min	Nominal distance in au	Min. possible distance in au	Distance uncert. in au
EARTH	1951-08-08 15:38	< 1 s	0.1936523	0.1936521	0.0000000
EARTH	1958-03-18 04:43	< 1 s	0.1515044	0.1515042	0.0000001
EARTH	1969-08-27 00:05	< 1 s	0.0606034	0.0606032	0.0000001
EARTH	1983-03-16 10:21	< 1 s	0.0894588	0.0894588	0.0000000
EARTH	1994-08-25 10:09	< 1 s	0.0333047	0.0333047	0.0000000
EARTH	2008-03-17 11:40	< 1 s	0.1251026	0.1251026	0.0000000
EARTH	2019-08-31 17:19	< 1 s	0.1372577	0.1372575	0.0000001
EARTH	2026-08-12 08:34	< 1 s	0.1704370	0.1704369	0.0000001
EARTH	2040-03-12 10:57	< 1 s	0.1136382	0.1136381	0.0000000
EARTH	2051-08-23 03:34	< 1 s	0.0478809	0.0478808	0.0000000
EARTH	2065-03-13 19:55	< 1 s	0.0965974	0.0965973	0.0000000
EARTH	2076-08-20 09:34	< 1 s	0.0783683	0.0783682	0.0000000
EARTH	2090-03-11 06:38	< 1 s	0.1508060	0.1508058	0.0000001
EARTH	2094-09-03 10:33	< 1 s	0.1900248	0.1900246	0.0000001
EARTH	2101-08-07 02:25	< 1 s	0.1980362	0.1980361	0.0000000
EARTH	2108-03-18 23:56	< 1 s	0.1395658	0.1395656	0.0000001
EARTH	2119-08-27 16:09	< 1 s	0.0336166	0.0336165	0.0000000

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Stationary Points

Ecc. an. ast.	Ecc. an. Earth	Distance in au	Classification
58.67334632	227.70095066	0.02953146	MINIMUM
299.52308851	69.30684244	0.08530387	MINIMUM
358.14083806	146.58700675	0.28225524	SADDLE
179.33985541	329.77020629	0.73961216	SADDLE
0.91211565	330.71188805	1.80151089	SADDLE
181.26455669	151.16010026	2.66168524	MAXIMUM

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MOID Plots

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