Asteroids

363027 1998ST27 help

Last update: 2026-03-17 23:26 UTC

Orbital Properties

Epoch

61200.0

MJD

Orbit type

Aten

Perihelion (q)

0.385

Aphelion (Q)

1.254

Eccentricity (e)

0.530

Inclination (i)

21.1

deg

Orbit period (P)

271.1

Earth MOID

0.00962

U parameter

0.0

A₂

16.4

10^-15au/days²

Next Earth close approach

Date

2027-10-09

Nominal distance (from Earth center)

0.15058

22526854

Maximum Brightness

19.1

mag

Risk

Object is not in risk list

Physical Properties

Absolute Magnitude (H)

19.5

mag

Diameter

400

Taxonomic type

Rotation period (T)

3.100

Discovery Information

Discovery Date

1998-09-24

Observatory

Lincoln Laboratory ETS, New Mexico

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

0.819811

1-sigma variation

2.602E-10

Unit

Eccentricity (e)

Value

0.529800

1-sigma variation

3.204E-8

Unit

Inclination (i)

Value

21.0514

1-sigma variation

3.296E-6

Unit

Long. of Ascending Node (Ω)

Value

197.5126

1-sigma variation

1.029E-6

Unit

Arg. of Perihelion (ω)

Value

322.4401

1-sigma variation

1.590E-6

Unit

Mean Anomaly (M)

Value

353.96838

1-sigma variation

4.016E-6

Unit

Perihelion distance

Value

0.385475

1-sigma variation

Unit

Aphelion distance

Value

1.254147

1-sigma variation

Unit

Asc. Node-Earth Sep.

Value

-0.585504

1-sigma variation

Unit

Desc. Node-Earth Sep.

Value

0.017619

1-sigma variation

Unit

MOID

Value

0.009619

1-sigma variation

Unit

Orbit Period

Value

271.1247

1-sigma variation

Unit

U parameter

Value

0.0

1-sigma variation

Unit

A₂

Value

16.39526

1-sigma variation

0.14455

Unit

10^-15au/days²

Covariance Matrix

	a	e	i	Ω	ω	M	A₂
a	6.76901E-20	4.87424E-18	-3.88068E-16	2.17765E-16	-3.35665E-16	6.55566E-16	2.38459E-11
e	4.87424E-18	1.02651E-15	-8.89980E-14	8.97115E-15	-1.00279E-14	1.28274E-13	-5.80044E-10
i	-3.88068E-16	-8.89980E-14	1.08656E-11	-1.05912E-12	1.04313E-12	-1.10194E-11	1.23442E-7
Ω	2.17765E-16	8.97115E-15	-1.05912E-12	1.05795E-12	-1.61759E-12	1.39208E-12	6.32510E-8
ω	-3.35665E-16	-1.00279E-14	1.04313E-12	-1.61759E-12	2.52671E-12	-1.69889E-12	-1.15828E-7
M	6.55566E-16	1.28274E-13	-1.10194E-11	1.39208E-12	-1.69889E-12	1.61318E-11	-5.68354E-8
A₂	2.38459E-11	-5.80044E-10	1.23442E-7	6.32510E-8	-1.15828E-7	-5.68354E-8	2.08946E-2

Date of computation: 2026-03-17 23:26 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

3.100

Unit

Source

[1]

Quality

Value

B,R

Unit

Source

[1]

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

19.541

Unit

mag

Source

[2]

Slope Parameter (G)

Value

0.15**

Unit

Source

[2]

Albedo
Diameter

Size and albedo

Value

Unit

Source

Albedo

Value

0.05

0.06

Unit

Source

[4]

[5]

Diameter

Value

400

Unit

Source

[3]

Color Index Information

Color Index Information

Value

Unit

Source

Color Index Information

Value

Unit

mag

Source

[-]

Sightings

Sightings

Value

Unit

Source

Sightings

Value

Radar R

Unit

Source

[6]

Satellites

Satellites

Value

Unit

Source

Satellites

Value

Binary Child 1

Unit

Source

[7]

Download this part as:

Sources

No.	Name	Additional
[1]	EARN	1.) Petr Pravec's Ondrejov NEO Photometric Program Webpage "Prepublished Periods" 2.) Pravec, P. et al (2016) Icarus 267,267-295. (Binary asteroid population. 3. Secondary rotations and elongations) (..,..)
[2]	ESA Aegis	ESA orbit determination and impact monitoring system
[3]	EARN	1.) Binzel, R.P. et al. (2002) in "Asteroids III" (Eds. W.F.Bottke et al.), Univ.Ariz.Press, Tucson, USA, pp. 255-271. (Physical Properties of NEOs)
[4]	EARN	1.) Benner, L. et al. (2003) DPS 35, 24.01. (Radar imaging of binary near-Earth asteroid 1998 ST27)
[5]	EARN	1.) Nugent, C.R. et al. (2016) Astron. J. 152_63 (12pp) (NEOWISE Reactivation Mission Year Two: Asteroid Diameters and Albedos) (207 NEOs)
[6]	EARN	1.) href="http://echo.jpl.nasa.gov/asteroids/index.html">JPL's NEO Radar Detection Program Webpage 2.) Benner, L.A.M. et al. (2001) I.A.U. Circ. HREF="http://www.cbat.eps.harvard.edu/iauc/07700/07730.html"> 7730. (1998 ST27) (Binary asteroid detection) 3.) Benner, L. et al. (2003) DPS 35, 24.01. (Radar imaging of binary near-Earth asteroid 1998 ST27)
[7]	EARN	Earth Asteroids Research Node: https://earn.dlr.de

Observational Information

Arc Length
Unobserved
Normalized RMS of residuals

Arc Information

Value

Unit

Source

Arc Length

Value

9518

Unit

Source

[1]

Unobserved

Value

595

Unit

Source

[1]

Normalized RMS of residuals

Value

0.514968

Unit

Source

[1]

Astrometry Summary

First Observation
Last Observation
Total Optical Observations (Discarded)

Optical

Value

Unit

Source

First Observation

Value

1998-09-24.16314

Unit

Source

[2]

Last Observation

Value

2024-10-14.785256

Unit

Source

[2]

Total Optical Observations (Discarded)

Value

1048 (15)

Unit

Source

[1]

Radar Summary

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

Radar

Value

Unit

Source

First Observation

Value

2001-10-07

Unit

Source

[3]

Last Observation

Value

2024-10-12

Unit

Source

[3]

Delay (Discarded)

Value

12 (0)

Unit

Source

[1]

Doppler (Discarded)

Value

1 (0)

Unit

Source

[1]

Total Radar Observations (Discarded)

Value

13 (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

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 363027 1998ST27 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	1955-10-10 11:51	< 1 s	0.1378248	0.1378246	0.0000001
EARTH	1958-10-11 23:24	< 1 s	0.0190269	0.0190265	0.0000001
MERCURY	1969-05-14 14:18	< 1 s	0.0062725	0.0062724	0.0000000
EARTH	1978-10-10 19:13	< 1 s	0.1257494	0.1257492	0.0000001
EARTH	1981-10-11 07:27	< 1 s	0.0497834	0.0497831	0.0000001
MERCURY	1987-11-28 06:15	< 1 s	0.0403245	0.0403244	0.0000000
MERCURY	1997-07-19 14:49	< 1 s	0.0105801	0.0105798	0.0000001
EARTH	2001-10-12 03:12	< 1 s	0.0617490	0.0617490	0.0000000
EARTH	2004-10-09 11:06	< 1 s	0.1209078	0.1209078	0.0000000
MERCURY	2016-02-02 14:01	< 1 s	0.0223387	0.0223383	0.0000001
EARTH	2021-10-07 01:03	< 1 s	0.1876735	0.1876735	0.0000000
EARTH	2024-10-12 01:51	< 1 s	0.0238045	0.0238045	0.0000000
EARTH	2027-10-09 10:14	< 1 s	0.1505827	0.1505827	0.0000000
MERCURY	2034-08-22 07:57	< 1 s	0.0195354	0.0195351	0.0000001
MERCURY	2043-07-19 09:28	< 1 s	0.0162228	0.0162226	0.0000001
EARTH	2047-10-12 15:53	< 1 s	0.0752324	0.0752322	0.0000001
EARTH	2050-10-10 22:09	< 1 s	0.0920054	0.0920051	0.0000001
MERCURY	2052-06-14 15:23	< 1 s	0.0466306	0.0466303	0.0000001
EARTH	2070-10-10 23:01	< 1 s	0.1297038	0.1297036	0.0000001
EARTH	2073-10-11 23:37	< 1 s	0.0338426	0.0338424	0.0000001
MERCURY	2079-12-01 10:20	< 1 s	0.0061762	0.0061762	0.0000000
EARTH	2093-10-10 20:05	< 1 s	0.1289148	0.1289140	0.0000002
EARTH	2096-10-11 15:58	< 1 s	0.0443869	0.0443859	0.0000003
MERCURY	2098-06-18 17:51	< 1 min	0.0132278	0.0132260	0.0000006
EARTH	2116-10-12 21:17	< 1 s	0.0892201	0.0892200	0.0000000
MERCURY	2117-01-02 14:15	< 1 s	0.0221381	0.0221380	0.0000000
EARTH	2119-10-12 12:48	< 1 s	0.0905671	0.0905668	0.0000001
MERCURY	2126-08-26 01:35	< 1 min	0.0484525	0.0484517	0.0000003

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Stationary Points

Ecc. an. ast.	Ecc. an. Earth	Distance in au	Classification
244.95808461	278.41493876	0.00981253	MINIMUM
116.97239259	202.51195718	0.35855113	MINIMUM
154.55761751	226.94251771	0.37366780	SADDLE
352.52660358	45.29039808	0.62459400	SADDLE
359.07226134	236.66542575	1.38822516	SADDLE
183.64925355	63.23424630	2.23385195	MAXIMUM

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MOID Plots

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