Asteroids

2021EP4 help

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

Orbital Properties

Epoch

61000.0

MJD

Orbit type

Apollo

Perihelion (q)

0.971

Aphelion (Q)

2.182

Eccentricity (e)

0.384

Inclination (i)

5.0

deg

Orbit period (P)

723.0

Earth MOID

0.00136

U parameter

5.9

Next Earth close approach

Date

2110-04-06

Nominal distance (from Earth center)

0.12257

18336801

Maximum Brightness

27.2

mag

Risk

Object is not in risk list

Physical Properties

Absolute Magnitude (H)

29.2

mag

Diameter

4 - 9*

Taxonomic type

Rotation period (T)

Discovery Information

Discovery Date

2021-03-15

Observatory

Tokyo-Kiso

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

1.576537

1-sigma variation

0.000063

Unit

Eccentricity (e)

Value

0.384155

1-sigma variation

0.000026

Unit

Inclination (i)

Value

5.0037

1-sigma variation

0.0006

Unit

Long. of Ascending Node (Ω)

Value

355.3378

1-sigma variation

0.0016

Unit

Arg. of Perihelion (ω)

Value

154.4654

1-sigma variation

0.0004

Unit

Mean Anomaly (M)

Value

141.32552

1-sigma variation

0.06108

Unit

Perihelion distance

Value

0.970902

1-sigma variation

Unit

Aphelion distance

Value

2.182172

1-sigma variation

Unit

Asc. Node-Earth Sep.

Value

1.051533

1-sigma variation

Unit

Desc. Node-Earth Sep.

Value

0.002137

1-sigma variation

Unit

MOID

Value

0.001363

1-sigma variation

Unit

Orbit Period

Value

723.0274

1-sigma variation

Unit

U parameter

Value

5.9

1-sigma variation

Unit

Covariance Matrix

	a	e	i	Ω	ω	M
a	4.03060E-9	1.62961E-9	3.81638E-8	-9.95048E-8	2.43334E-8	-3.87803E-6
e	1.62961E-9	6.58872E-10	1.54300E-8	-4.02307E-8	9.83249E-9	-1.56792E-6
i	3.81638E-8	1.54300E-8	3.61527E-7	-9.42158E-7	2.30331E-7	-3.67191E-5
Ω	-9.95048E-8	-4.02307E-8	-9.42158E-7	2.45651E-6	-6.00719E-7	9.57383E-5
ω	2.43334E-8	9.83249E-9	2.30331E-7	-6.00719E-7	1.51133E-7	-2.34141E-5
M	-3.87803E-6	-1.56792E-6	-3.67191E-5	9.57383E-5	-2.34141E-5	3.73124E-3

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

29.182

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

4 - 9*

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

1650

Unit

Source

[1]

Normalized RMS of residuals

Value

0.773464

Unit

Source

[1]

Astrometry Summary

First Observation
Last Observation
Total Optical Observations (Discarded)

Optical

Value

Unit

Source

First Observation

Value

2021-03-15.458495

Unit

Source

[2]

Last Observation

Value

2021-03-18.308412

Unit

Source

[2]

Total Optical Observations (Discarded)

Value

67 (4)

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 2021EP4 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	1953-03-30 07:31	> 1 mo	0.0821904	0.0042479	0.5285595
EARTH	1955-01-11 20:06	> 1 mo	0.1122916	0.0666329	0.4461381
EARTH	1990-03-09 06:30	> 1 d	0.0161798	0.0009868	0.0090943
EARTH	2021-03-15 18:08	< 1 s	0.0024841	0.0024836	0.0000002
EARTH	2023-02-14 01:55	434.5	0.0482733	0.0473298	0.0003187
EARTH	2025-01-16 10:45	326.1	0.1076021	0.1035760	0.0013574
EARTH	2110-04-06 19:30	> 1 d	0.1225739	0.0525932	0.0234764
EARTH	2112-03-21 02:38	> 1 d	0.0167423	0.0004832	0.0167275
EARTH	2114-03-12 21:07	> 1 w	0.0090782	0.0011774	0.0358502
EARTH	2116-01-28 23:37	> 1 mo	0.0734661	0.0544763	0.1726558
EARTH	2118-01-08 09:16	> 1 mo	0.1944370	0.0710021	0.6384342

Download as:

Stationary Points

Ecc. an. ast.	Ecc. an. Earth	Distance in au	Classification
16.53148849	71.25482438	0.00196005	MINIMUM
180.42441624	228.25339732	1.17262240	SADDLE
1.57552615	229.26467610	1.98137143	SADDLE
180.88772489	48.55625065	3.17066376	MAXIMUM

Download:

MOID Plots

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