Asteroids

2011UD21 help

Last update: 2025-09-10 00:30 UTC

Orbital Properties

Epoch

61000.0

MJD

Orbit type

Aten

Perihelion (q)

0.949

Aphelion (Q)

1.008

Eccentricity (e)

0.030

Inclination (i)

1.1

deg

Orbit period (P)

353.6

Earth MOID

0.00323

U parameter

4.2

Next Earth close approach

Date

2041-09-29

Nominal distance (from Earth center)

0.07873

11777605

Maximum Brightness

26.2

mag

Risk

Object is in risk list

Physical Properties

Absolute Magnitude (H)

28.5

mag

Diameter

5 - 12*

Taxonomic type

Rotation period (T)

Discovery Information

Discovery Date

2011-10-18

Observatory

Mt. Lemmon Survey

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

61000.0000

1-sigma variation

Unit

MJD

Semimajor Axis

Value

0.978648

1-sigma variation

0.000002

Unit

Eccentricity (e)

Value

0.030361

1-sigma variation

0.000004

Unit

Inclination (i)

Value

1.0611

1-sigma variation

0.0001

Unit

Long. of Ascending Node (Ω)

Value

22.3464

1-sigma variation

0.0007

Unit

Arg. of Perihelion (ω)

Value

209.8903

1-sigma variation

0.0035

Unit

Mean Anomaly (M)

Value

350.36774

1-sigma variation

0.01183

Unit

Perihelion distance

Value

0.948935

1-sigma variation

Unit

Aphelion distance

Value

1.008361

1-sigma variation

Unit

Asc. Node-Earth Sep.

Value

0.006877

1-sigma variation

Unit

Desc. Node-Earth Sep.

Value

-0.051160

1-sigma variation

Unit

MOID

Value

0.003232

1-sigma variation

Unit

Orbit Period

Value

353.6211

1-sigma variation

Unit

U parameter

Value

4.2

1-sigma variation

Unit

Covariance Matrix

	a	e	i	Ω	ω	M
a	3.88497E-12	-7.48350E-12	-1.75795E-10	-1.38136E-9	-6.80327E-9	-2.33055E-8
e	-7.48350E-12	1.44193E-11	3.38809E-10	2.66219E-9	1.31245E-8	4.48701E-8
i	-1.75795E-10	3.38809E-10	7.97217E-9	6.25888E-8	3.08634E-7	1.05364E-6
Ω	-1.38136E-9	2.66219E-9	6.25888E-8	4.91822E-7	2.42520E-6	8.27925E-6
ω	-6.80327E-9	1.31245E-8	3.08634E-7	2.42520E-6	1.20198E-5	4.06909E-5
M	-2.33055E-8	4.48701E-8	1.05364E-6	8.27925E-6	4.06909E-5	1.39947E-4

Date of computation: 2025-09-10 00:30 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

Unit

Source

[-]

Quality

Value

Unit

Source

[-]

Amplitude

Value

Unit

mag

Source

[-]

Rotation Direction

Value

Unit

Source

[-]

Spinvector L

Value

Unit

Source

[-]

Spinvector B

Value

Unit

Source

[-]

Taxonomy
Taxonomy (all)

Taxonomy

Value

Unit

Source

Taxonomy

Value

Unit

Source

[-]

Taxonomy (all)

Value

Unit

Source

[-]

Absolute Magnitude (H)
Slope Parameter (G)

H / G

Value

Unit

Source

Absolute Magnitude (H)

Value

28.541

Unit

mag

Source

[1]

Slope Parameter (G)

Value

0.15**

Unit

mag

Source

[1]

Albedo
Diameter

Size and albedo

Value

Unit

Source

Albedo

Value

0.05 - 0.25

Unit

Source

[2]

Diameter

Value

5 - 12*

Unit

Source

[2]

Color Index Information

Color Index Information

Value

Unit

Source

Color Index Information

Value

Unit

mag

Source

[-]

Sightings

Sightings

Value

Unit

Source

Sightings

Value

Unit

Source

[-]

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Sources

No.	Name	Additional
[1]	ESA Aegis	ESA orbit determination and impact monitoring system
[2]	Estimation	Estimated from absolute magnitude

Observational Information

Arc Length
Unobserved
Normalized RMS of residuals

Arc Information

Value

Unit

Source

Arc Length

Value

Unit

Source

[1]

Unobserved

Value

5055

Unit

Source

[1]

Normalized RMS of residuals

Value

0.554268

Unit

Source

[1]

Astrometry Summary

First Observation
Last Observation
Total Optical Observations (Discarded)

Optical

Value

Unit

Source

First Observation

Value

2011-10-18.41958

Unit

Source

[2]

Last Observation

Value

2011-11-24.235388

Unit

Source

[2]

Total Optical Observations (Discarded)

Value

90 (1)

Unit

Source

[1]

Radar Summary

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

Radar

Value

Unit

Source

First Observation

Value

Unit

Source

[-]

Last Observation

Value

Unit

Source

[-]

Delay (Discarded)

Value

0 (0)

Unit

Source

[-]

Doppler (Discarded)

Value

0 (0)

Unit

Source

[-]

Total Radar Observations (Discarded)

Value

0 (0)

Unit

Source

[-]

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

Computation parameters

As seen from:

Initial Date: *

Final Date: *

Output option:

One line per time step

Time step:*

* - these fields are required

Close Approaches for 2011UD21 from 1950 to 2125

Body	Date in UTC	Time uncert. in min	Nominal distance in au	Min. possible distance in au	Distance uncert. in au
EARTH	1950-06-01 23:21	> 1 mo	0.0187225	0.0023172	23.7069376
EARTH	1977-02-01 14:34	> 1 mo	0.1274549	0.0112918	1.3504239
EARTH	1977-11-14 04:10	> 1 mo	0.0567829	0.0565525	0.0227678
EARTH	1978-05-20 14:02	> 1 d	0.0041727	0.0008938	0.0180235
EARTH	1979-01-10 18:12	> 1 w	0.0587548	0.0474795	0.0037796
EARTH	1979-10-10 00:32	756.8	0.0327601	0.0071853	0.0092787
EARTH	2009-05-20 07:43	25.0	0.0164404	0.0163466	0.0000313
EARTH	2010-04-06 17:34	428.1	0.0365516	0.0364064	0.0000484
EARTH	2010-07-04 21:02	293.9	0.0315741	0.0314792	0.0000316
EARTH	2011-01-13 17:40	225.1	0.0514701	0.0514448	0.0000084
EARTH	2011-10-13 14:51	< 1 min	0.0048800	0.0048786	0.0000005
EARTH	2012-04-22 03:48	3.3	0.0546943	0.0546781	0.0000054
EARTH	2013-02-01 09:32	< 1 min	0.1088595	0.1088078	0.0000172
EARTH	2041-09-29 20:49	5.3	0.0787284	0.0770452	0.0005611
EARTH	2042-06-25 17:03	> 1 d	0.0605882	0.0604889	0.0000332
EARTH	2043-02-02 17:43	106.8	0.0190089	0.0185820	0.0001473
EARTH	2063-10-15 05:55	65.8	0.1668457	0.1590869	0.0025864
EARTH	2064-07-16 16:23	> 1 w	0.0686627	0.0668258	0.0006126
EARTH	2065-01-30 15:45	11.0	0.0380960	0.0312356	0.0023558
EARTH	2082-10-18 10:08	649.5	0.0897146	0.0067295	0.0675694
EARTH	2083-05-23 06:35	> 1 mo	0.0792068	0.0595973	0.0088453
EARTH	2084-01-28 05:26	365.0	0.1564311	0.0174797	0.0511954
EARTH	2101-10-19 15:46	> 1 d	0.1457400	0.0060399	0.2898272
EARTH	2102-06-23 02:16	> 1 mo	0.0805823	0.0506353	0.0180486
EARTH	2103-01-30 11:42	> 1 d	0.0987551	0.0168979	0.2804324
EARTH	2120-10-18 07:30	> 1 d	0.0755488	0.0070180	1.0099476
EARTH	2121-05-18 04:10	> 1 mo	0.0768302	0.0478538	0.1746228
EARTH	2122-01-29 09:20	> 1 w	0.1617270	0.0176938	0.6364185

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Stationary Points

Ecc. an. ast.	Ecc. an. Earth	Distance in au	Classification
139.31191821	271.28077160	0.00352229	MINIMUM
261.92188091	29.64584201	0.01745087	MINIMUM
207.36765962	336.84607982	0.02533740	SADDLE
21.32703636	151.40017812	0.06500132	SADDLE
17.59151729	327.51252796	1.93635047	SADDLE
196.99157197	146.91239376	2.02062972	MAXIMUM

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MOID Plots

Click on the images to zoom-in and zoom-out

Level lines of the squared distance function

2011UD21

Date in UTC	MJD	σ	σ_imp	Distance ± Width in RE	Stretching in RE	IP	Impact energy	PS	TS
2105-02-20.866	89945.866	-0.337	0.000	3.78 ± 0.034	2.55E6	2.34E-6	6.50E-3	-7.76	0
2116-03-02.475	93973.475	-0.939	0.000	2.21 ± 0.016	2.75E7	1.52E-7	6.49E-3	-9.00	0


Based on 90 optical observations (of which 1 are rejected as outliers) from 2011/10/18.420 to 2011/11/24.235.
Coordinates are given on the Target Plane.
Unit is one Earth radius, but impact cross section has radius between 8.76 and 8.76 Earth radii.
Coordinates for LOV = EQU scaled= 1 second= F.
AstOD software version= 4.0, Date of computation=20250805 130500.123 UTC.

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Download Impactor Table as: