Asteroids

2021AD4 help

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

Orbital Properties

Epoch

61000.0

MJD

Orbit type

Aten

Perihelion (q)

0.827

Aphelion (Q)

0.987

Eccentricity (e)

0.088

Inclination (i)

9.5

deg

Orbit period (P)

315.6

Earth MOID

0.00065

U parameter

6.5

Next Earth close approach

Date

2027-06-24

Nominal distance (from Earth center)

0.1844

27585889

Maximum Brightness

35.7

mag

Risk

Object is not in risk list

Physical Properties

Absolute Magnitude (H)

25.6

mag

Diameter

21 - 50*

Taxonomic type

Rotation period (T)

Discovery Information

Discovery Date

2021-01-09

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

0.907236

1-sigma variation

0.000045

Unit

Eccentricity (e)

Value

0.088131

1-sigma variation

0.000054

Unit

Inclination (i)

Value

9.4632

1-sigma variation

0.0075

Unit

Long. of Ascending Node (Ω)

Value

106.5497

1-sigma variation

0.0014

Unit

Arg. of Perihelion (ω)

Value

194.2235

1-sigma variation

0.0003

Unit

Mean Anomaly (M)

Value

33.94027

1-sigma variation

0.14722

Unit

Perihelion distance

Value

0.827280

1-sigma variation

Unit

Aphelion distance

Value

0.987191

1-sigma variation

Unit

Asc. Node-Earth Sep.

Value

0.000655

1-sigma variation

Unit

Desc. Node-Earth Sep.

Value

-0.188744

1-sigma variation

Unit

MOID

Value

0.000648

1-sigma variation

Unit

Orbit Period

Value

315.6303

1-sigma variation

Unit

U parameter

Value

6.5

1-sigma variation

Unit

Covariance Matrix

	a	e	i	Ω	ω	M
a	2.00022E-9	-2.42198E-9	-3.36439E-7	-6.03807E-8	7.69479E-9	-6.58420E-6
e	-2.42198E-9	2.93270E-9	4.07404E-7	7.31188E-8	-9.29567E-9	7.97251E-6
i	-3.36439E-7	4.07404E-7	5.66334E-5	1.01679E-5	-1.26737E-6	1.10743E-3
Ω	-6.03807E-8	7.31188E-8	1.01679E-5	1.82598E-6	-2.25286E-7	1.98747E-4
ω	7.69479E-9	-9.29567E-9	-1.26737E-6	-2.25286E-7	7.25194E-8	-2.53851E-5
M	-6.58420E-6	7.97251E-6	1.10743E-3	1.98747E-4	-2.53851E-5	2.16736E-2

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

25.558

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

21 - 50*

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

[-]

Download this part as:

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

1706

Unit

Source

[1]

Normalized RMS of residuals

Value

0.575044

Unit

Source

[1]

Astrometry Summary

First Observation
Last Observation
Total Optical Observations (Discarded)

Optical

Value

Unit

Source

First Observation

Value

2021-01-09.536105

Unit

Source

[2]

Last Observation

Value

2021-01-18.51067

Unit

Source

[2]

Total Optical Observations (Discarded)

Value

42 (0)

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 2021AD4 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	1950-06-24 14:53	> 1 mo	0.1894029	0.1893351	0.0027536
EARTH	1956-07-21 19:14	> 1 mo	0.1955316	0.1946898	0.0081232
EARTH	1969-01-17 23:55	> 1 d	0.1078208	0.0246514	0.0475583
EARTH	1975-01-06 23:19	231.7	0.0106012	0.0046519	0.0020249
EARTH	1981-07-30 15:31	988.9	0.1909267	0.1907928	0.0000548
EARTH	1988-01-02 17:28	197.0	0.0885008	0.0749063	0.0045385
EARTH	1988-05-13 22:39	> 1 d	0.1843307	0.1842870	0.0000826
EARTH	2001-06-17 05:59	> 1 d	0.1795963	0.1795947	0.0000126
EARTH	2008-01-16 06:46	607.9	0.0924618	0.0759002	0.0055473
EARTH	2014-07-09 01:04	> 1 d	0.1828748	0.1822763	0.0002502
EARTH	2021-01-08 23:47	< 1 min	0.0239317	0.0238781	0.0000179
EARTH	2027-06-24 05:28	> 1 d	0.1844003	0.1843840	0.0000303
EARTH	2040-01-03 03:13	442.4	0.0692693	0.0476980	0.0072180
EARTH	2040-05-06 15:10	> 1 d	0.1859631	0.1859555	0.0000232
EARTH	2046-07-24 16:34	> 1 d	0.1914848	0.1906085	0.0003332
EARTH	2053-01-10 03:51	187.1	0.0393577	0.0353720	0.0013300
EARTH	2059-06-14 03:44	> 1 d	0.1847926	0.1847912	0.0000052
EARTH	2072-01-10 06:10	727.0	0.0327600	0.0169192	0.0053250
EARTH	2077-12-30 15:29	89.4	0.1499985	0.1235323	0.0088435
EARTH	2078-05-28 13:13	> 1 d	0.1875538	0.1871951	0.0004777
EARTH	2084-07-09 04:34	> 1 w	0.1913635	0.1911734	0.0007901
EARTH	2097-01-12 23:22	> 1 d	0.0669126	0.0114877	0.0387657
EARTH	2103-01-03 00:41	1119.7	0.0739662	0.0185739	0.0190816
EARTH	2103-05-08 11:30	> 1 w	0.1879704	0.1877547	0.0007717
EARTH	2109-06-22 06:40	> 1 w	0.1878031	0.1876949	0.0004814
EARTH	2115-07-30 14:14	> 1 w	0.1988805	0.1982347	0.0032616
EARTH	2122-01-24 18:41	> 1 d	0.1762048	0.0506239	0.0780221

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Stationary Points

Ecc. an. ast.	Ecc. an. Earth	Distance in au	Classification
164.41329192	4.19166426	0.00056990	MINIMUM
327.15949763	162.78706207	0.18406196	MINIMUM
291.47058950	124.68952457	0.18693612	SADDLE
42.54978736	245.30536922	0.20647647	SADDLE
358.38797540	16.94016424	1.81138783	SADDLE
175.76738174	194.29031284	2.00253912	MAXIMUM

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MOID Plots

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