Asteroids

2021UA1 help

Last update: 2026-06-04 23:11 UTC

Orbital Properties

Epoch

61200.0

MJD

Orbit type

Apollo

Perihelion (q)

0.646

Aphelion (Q)

1.525

Eccentricity (e)

0.405

Inclination (i)

5.991E-3

deg

Orbit period (P)

413.1

Earth MOID

0.00004

U parameter

6.4

Next Earth close approach

Date

2028-03-31

Nominal distance (from Earth center)

0.11488

17186412

Maximum Brightness

29.8

mag

Risk

Object is in risk list

Physical Properties

Absolute Magnitude (H)

31.6

mag

Diameter

1.3 - 2.8*

Taxonomic type

Rotation period (T)

Discovery Information

Discovery Date

2021-10-25

Observatory

University of Arizona Catalina Sky 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

61200.0000

1-sigma variation

Unit

MJD

Semimajor Axis

Value

1.085551

1-sigma variation

0.000052

Unit

Eccentricity (e)

Value

0.404709

1-sigma variation

0.000066

Unit

Inclination (i)

Value

0.0060

1-sigma variation

3.273E-6

Unit

Long. of Ascending Node (Ω)

Value

125.5437

1-sigma variation

0.4765

Unit

Arg. of Perihelion (ω)

Value

163.6460

1-sigma variation

0.4766

Unit

Mean Anomaly (M)

Value

86.11068

1-sigma variation

0.11290

Unit

Perihelion distance

Value

0.646219

1-sigma variation

Unit

Aphelion distance

Value

1.524883

1-sigma variation

Unit

Asc. Node-Earth Sep.

Value

0.530149

1-sigma variation

Unit

Desc. Node-Earth Sep.

Value

-0.368560

1-sigma variation

Unit

MOID

Value

0.000044

1-sigma variation

Unit

Orbit Period

Value

413.1177

1-sigma variation

Unit

U parameter

Value

6.4

1-sigma variation

Unit

Covariance Matrix

	a	e	i	Ω	ω	M
a	2.67683E-9	3.43001E-9	1.01441E-10	1.07500E-5	-1.07549E-5	-5.84120E-6
e	3.43001E-9	4.39744E-9	1.31431E-10	1.40290E-5	-1.40356E-5	-7.48481E-6
i	1.01441E-10	1.31431E-10	1.07108E-11	1.52488E-6	-1.52518E-6	-2.21422E-7
Ω	1.07500E-5	1.40290E-5	1.52488E-6	2.27078E-1	-2.27118E-1	-2.34693E-2
ω	-1.07549E-5	-1.40356E-5	-1.52518E-6	-2.27118E-1	2.27158E-1	2.34801E-2
M	-5.84120E-6	-7.48481E-6	-2.21422E-7	-2.34693E-2	2.34801E-2	1.27463E-2

Date of computation: 2026-06-04 23:11 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

31.633

Unit

mag

Source

[1]

Slope Parameter (G)

Value

0.15**

Unit

Source

[1]

Albedo
Diameter

Size and albedo

Value

Unit

Source

Albedo

Value

0.05 - 0.25

Unit

Source

[2]

Diameter

Value

1.3 - 2.8*

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

0.9

Unit

Source

[1]

Unobserved

Value

1728

Unit

Source

[1]

Normalized RMS of residuals

Value

0.730196

Unit

Source

[1]

Astrometry Summary

First Observation
Last Observation
Total Optical Observations (Discarded)

Optical

Value

Unit

Source

First Observation

Value

2021-10-25.255448

Unit

Source

[2]

Last Observation

Value

2021-10-26.116061

Unit

Source

[2]

Total Optical Observations (Discarded)

Value

23 (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

Filters

Initial Date: *

Final Date: *

Normalised Only accepted

Max residual (arcsec):

* - these fields are required

Plot

Computation parameters

As seen from:

Initial Date: *

Final Date: *

Output option:

One line per time step

Time step:*

* - these fields are required

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 2021UA1 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	1956-03-18 03:55	> 1 d	0.1570188	0.1237971	0.0425164
EARTH	1957-03-08 09:12	> 1 d	0.1335186	0.1219420	0.0274472
EARTH	1984-10-28 18:05	399.9	0.1228576	0.0977313	0.0083755
EARTH	1985-10-24 05:07	329.9	0.0319785	0.0007683	0.0116641
EARTH	1986-10-28 16:07	> 1 d	0.1902379	0.1568690	0.0111329
EARTH	1994-03-16 17:39	1120.2	0.1443355	0.1295336	0.0060593
EARTH	1995-03-07 04:33	755.8	0.1497744	0.1332945	0.0064620
EARTH	2020-10-30 08:34	27.3	0.1615942	0.1599052	0.0005630
EARTH	2021-10-25 03:06	< 1 min	0.0000630	0.0000630	0.0000000
EARTH	2028-03-31 12:05	149.4	0.1148841	0.1054054	0.0031595
EARTH	2038-10-18 21:52	26.3	0.1906186	0.1755052	0.0050378
VENUS	2041-12-14 08:29	> 1 d	0.0466703	0.0347781	0.0040672
EARTH	2045-03-24 02:19	185.8	0.0735260	0.0639856	0.0031801
EARTH	2047-10-30 13:12	98.9	0.1141384	0.1105392	0.0011997
EARTH	2064-10-22 20:29	564.0	0.0541622	0.0233297	0.0102775
EARTH	2071-03-29 16:58	284.3	0.0474073	0.0304804	0.0056424
EARTH	2088-03-20 08:53	1378.9	0.1581069	0.0870759	0.0236771
EARTH	2090-10-26 19:25	> 1 d	0.0280248	0.0003222	0.0264900
EARTH	2105-03-20 08:07	> 1 d	0.1981545	0.0001719	0.1017297
EARTH	2107-10-27 19:51	> 1 d	0.0203281	0.0003658	0.1145696
EARTH	2122-03-29 20:07	> 1 mo	0.0094982	0.0002708	0.8834303

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Stationary Points

Ecc. an. ast.	Ecc. an. Earth	Distance in au	Classification
78.04678942	291.26670670	0.00006858	MINIMUM
281.36373324	83.85749961	0.00007750	MINIMUM
359.54631018	187.38830802	0.37177598	SADDLE
179.80708478	7.67343610	0.54120014	SADDLE
359.56068411	7.40402407	1.62993133	SADDLE
179.80054005	187.66628030	2.54290708	MAXIMUM

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MOID Plots

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

Level lines of the squared distance function

2021UA1

Date in UTC	MJD	σ	Distance ± Width in RE	Stretching in RE	IP	Impact energy	PS
2071-03-27.350	77562.350	-3.637	1.02 ± 0.008	2.51E3	3.58E-7	1.45E-4	-9.66
2076-10-24.940	79600.940	-4.571	0.72 ± 0.000	1.16E6	2.27E-11	1.45E-4	-13.91
2079-03-27.416	80484.416	-3.604	1.26 ± 0.008	4.26E5	1.10E-9	1.45E-4	-12.24
2079-10-19.250	80690.250	-3.627	0.80 ± 0.029	4.76E6	2.48E-10	1.45E-4	-12.90
2080-03-26.516	80849.516	-3.992	0.91 ± 0.008	3.97E3	6.71E-8	1.45E-4	-10.46
2080-03-26.568	80849.568	-4.052	0.92 ± 0.008	1.02E4	2.03E-8	1.45E-4	-10.98
2080-03-26.615	80849.615	-3.815	1.09 ± 0.008	9.48E3	5.30E-8	1.45E-4	-10.57
2081-03-26.790	81214.790	-3.667	1.26 ± 0.008	7.09E5	5.71E-10	1.45E-4	-12.54
2084-10-29.324	82527.324	4.578	0.22 ± 0.032	2.71E5	1.08E-10	1.45E-4	-13.29
2087-10-26.112	83619.112	-4.876	0.07 ± 0.001	2.62E5	2.77E-11	1.45E-4	-13.91
2088-03-26.539	83771.539	-3.974	1.17 ± 0.008	8.16E5	4.01E-10	1.45E-4	-12.74
2088-10-22.627	83981.627	4.254	0.14 ± 0.004	2.84E5	4.36E-10	1.45E-4	-12.71
2091-03-27.314	84867.314	-4.047	0.92 ± 0.008	5.24E6	4.05E-11	1.45E-4	-13.76
2094-03-28.389	85964.389	4.256	1.11 ± 0.008	4.30E5	1.54E-10	1.45E-4	-13.20
2095-10-30.123	86545.123	4.548	0.86 ± 0.028	2.10E6	1.22E-11	1.46E-4	-14.31
2096-03-26.637	86693.637	-3.997	0.75 ± 0.008	1.58E7	1.88E-11	1.45E-4	-14.12
2098-10-27.782	87638.782	3.077	0.45 ± 0.015	2.83E7	3.08E-10	1.45E-4	-12.92
2099-03-26.259	87788.259	-4.352	0.82 ± 0.009	5.29E5	1.47E-10	1.46E-4	-13.25
2101-10-22.032	88728.032	4.338	0.87 ± 0.014	1.09E6	6.10E-11	1.45E-4	-13.65
2104-10-22.379	89824.379	3.046	1.14 ± 0.006	1.55E6	5.10E-9	1.45E-4	-11.74
2106-03-24.735	90342.735	3.527	1.21 ± 0.009	3.32E7	6.07E-11	1.46E-4	-13.67
2106-03-28.040	90346.040	-3.926	0.56 ± 0.008	5.49E4	7.84E-9	1.45E-4	-11.56
2106-03-28.087	90346.087	-3.850	0.50 ± 0.008	8.45E4	6.98E-9	1.45E-4	-11.61
2108-03-27.803	91076.803	-3.709	0.53 ± 0.008	2.29E5	4.40E-9	1.45E-4	-11.82
2110-03-28.280	91807.280	-2.243	1.28 ± 0.000	3.95E7	1.88E-9	1.45E-4	-12.20
2111-10-31.788	92389.788	-2.729	1.00 ± 0.033	1.75E6	9.66E-9	1.45E-4	-11.50
2112-03-28.597	92538.597	3.942	1.32 ± 0.007	5.24E5	8.42E-10	1.45E-4	-12.56
2112-03-30.288	92540.288	-0.980	0.95 ± 0.007	4.27E5	1.07E-6	1.45E-4	-9.45
2112-10-24.132	92748.132	4.249	0.86 ± 0.004	7.98E5	1.21E-10	1.45E-4	-13.40
2112-10-25.638	92749.638	-1.047	0.31 ± 0.000	6.93E7	8.80E-9	1.45E-4	-11.54
2112-11-02.289	92757.289	-3.647	0.66 ± 0.059	3.90E6	3.02E-10	1.45E-4	-13.01
2113-10-24.354	93113.354	3.063	0.42 ± 0.003	7.03E6	1.32E-9	1.45E-4	-12.37
2114-03-28.234	93268.234	-3.514	1.00 ± 0.008	1.03E5	1.41E-8	1.45E-4	-11.34
2114-10-23.712	93477.712	-2.608	1.02 ± 0.005	1.07E6	2.34E-8	1.45E-4	-11.13
2114-10-23.743	93477.743	-2.390	0.99 ± 0.006	7.81E5	5.41E-8	1.45E-4	-10.76
2114-10-25.721	93479.721	3.079	0.88 ± 0.002	9.85E6	6.99E-10	1.46E-4	-12.65
2115-03-28.921	93633.921	-1.998	0.42 ± 0.007	2.00E5	6.97E-7	1.45E-4	-9.65
2115-03-29.432	93634.432	-1.638	0.51 ± 0.007	6.42E6	4.23E-8	1.45E-4	-10.87
2115-03-29.492	93634.492	-1.581	0.52 ± 0.007	1.85E7	1.51E-8	1.45E-4	-11.32
2115-03-29.595	93634.595	-1.932	0.96 ± 0.007	1.06E7	1.05E-8	1.46E-4	-11.47
2115-10-23.210	93842.210	-1.679	1.16 ± 0.012	3.39E6	6.66E-8	1.45E-4	-10.68
2115-10-27.160	93846.160	0.129	0.38 ± 0.000	6.30E5	1.62E-6	1.44E-4	-9.29
2116-10-24.986	94209.986	-3.859	0.30 ± 0.001	7.74E6	7.77E-11	1.45E-4	-13.61
2117-03-28.228	94364.228	-3.707	1.03 ± 0.008	1.82E6	3.80E-10	1.45E-4	-12.93
2119-10-20.946	95300.946	-2.305	0.85 ± 0.021	7.56E6	9.73E-9	1.45E-4	-11.53
2119-10-23.954	95303.954	3.047	1.07 ± 0.009	2.28E7	4.28E-10	1.45E-4	-12.89
2119-10-26.855	95306.855	-1.064	0.04 ± 0.000	1.03E7	5.81E-8	1.45E-4	-10.75
2120-03-28.509	95460.509	3.954	0.80 ± 0.007	3.62E5	9.38E-10	1.45E-4	-12.55
2122-03-28.704	96190.704	3.398	0.48 ± 0.008	1.55E4	2.03E-7	1.45E-4	-10.22


Based on 23 optical observations (of which 1 are rejected as outliers) from 2021/10/25.255 to 2021/10/26.116.
Coordinates are given on the Target Plane.
Unit is one Earth radius, but impact cross section has radius between 1.32 and 1.32 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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