| Parameter |
Value |
| Designation |
C/2018 A3 (ATLAS) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2019-01-12T20:43:26.261760Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:33:39Z |
| Obs used |
1589 |
| NEO |
- |
| M1 |
9.400 |
| K1 |
9.000 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2018-12-07.0000000 |
| e |
0.99339311 |
| q (au) |
3.276715 |
| a (au) |
495.953962 |
| i (deg) |
139.561983 |
| Ω (om, deg) |
194.279275 |
| ω (w, deg) |
86.426299 |
| M (ma, deg) |
359.996710 |
Magnitude
Scatter + Global Linear
$$
M_a = (10.483 + 3.260\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
10.483 |
| n |
3.260 |
| gf |
0.990 |
| gb |
-0.500 |
| k |
0.800 |
| δ90 |
3.460 |
| Parameter |
Symbol |
Range |
Description |
| Absolute magnitude at 1 AU from Sun and Earth |
H0 |
-5 to 20 |
Intrinsic brightness of the comet |
| Photometric slope parameter |
n |
2 to 6 |
Rate of brightness change with heliocentric distance |
| Forward scattering asymmetry factor |
gf |
0.8 to 1 |
Degree of forward scattering |
| Backward scattering asymmetry factor |
gb |
-1 to -0.5 |
Degree of backward scattering |
| Partitioning coefficient |
k |
0.8 to 1 |
Ratio between forward/backward scattering contributions |
| Dust-to-gas brightness ratio |
δ90 |
1 to 10 |
Relative contribution of dust scattering to gas emission |
Reference: EPSC-DPS2025-160
Residuals (Piecewise)
$$\epsilon = a \log_{10} r_{\mathrm{au}} + b$$
| Start (UTC) |
End (UTC) |
a |
b |
| 2018-01-10 |
2019-01-12 |
+0.8638 |
-0.847 |
| 2019-01-12 |
2019-10-05 |
-2.0619 |
+1.339 |
| 2019-10-05 |
2020-10-24 |
+4.9812 |
-2.845 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-09-20 00:00 |
23:39:09.09 |
-29:19:50.1 |
HIP 116649 |
10.57 |
| 2026-09-20 12:00 |
23:39:01.75 |
-29:20:32.3 |
HIP 116649 |
8.88 |
| 2026-09-21 00:00 |
23:38:54.42 |
-29:21:14.0 |
HIP 116649 |
7.23 |
| 2026-09-21 12:00 |
23:38:47.09 |
-29:21:55.3 |
HIP 116649 |
5.63 |
| 2026-09-22 00:00 |
23:38:39.77 |
-29:22:36.1 |
HIP 116649 |
4.15 |
| 2026-09-22 12:00 |
23:38:32.45 |
-29:23:16.5 |
HIP 116649 |
2.96 |
| 2026-09-23 00:00 |
23:38:25.14 |
-29:23:56.4 |
HIP 116649 |
2.50 |
| 2026-09-23 12:00 |
23:38:17.85 |
-29:24:35.9 |
HIP 116649 |
3.10 |
| 2026-09-24 00:00 |
23:38:10.56 |
-29:25:14.9 |
HIP 116649 |
4.34 |
| 2026-09-24 12:00 |
23:38:03.27 |
-29:25:53.5 |
HIP 116649 |
5.82 |
| 2026-09-25 00:00 |
23:37:56.00 |
-29:26:31.6 |
HIP 116649 |
7.39 |
| 2026-09-25 12:00 |
23:37:48.74 |
-29:27:09.3 |
HIP 116649 |
9.01 |
| 2026-09-26 00:00 |
23:37:41.49 |
-29:27:46.5 |
HIP 116649 |
10.64 |
| 2026-09-26 12:00 |
23:37:34.26 |
-29:28:23.2 |
HIP 116649 |
12.29 |
| 2026-09-27 00:00 |
23:37:27.03 |
-29:28:59.5 |
HIP 116649 |
13.94 |
| 2026-09-27 12:00 |
23:37:19.82 |
-29:29:35.3 |
HIP 116649 |
15.59 |
| 2026-09-28 00:00 |
23:37:12.62 |
-29:30:10.6 |
HIP 116649 |
17.24 |
| 2026-09-28 12:00 |
23:37:05.43 |
-29:30:45.5 |
HIP 116649 |
18.89 |
| 2026-09-29 00:00 |
23:36:58.26 |
-29:31:19.9 |
HIP 116649 |
20.53 |
| 2026-09-29 12:00 |
23:36:51.10 |
-29:31:53.8 |
HIP 116649 |
22.17 |
| 2026-09-30 00:00 |
23:36:43.96 |
-29:32:27.2 |
HIP 116649 |
23.81 |
| 2026-09-30 12:00 |
23:36:36.84 |
-29:33:00.2 |
HIP 116453 |
25.23 |
| 2026-10-01 00:00 |
23:36:29.73 |
-29:33:32.7 |
HIP 116453 |
24.13 |
| 2026-10-01 12:00 |
23:36:22.64 |
-29:34:04.7 |
HIP 116453 |
23.10 |
| 2026-10-02 00:00 |
23:36:15.57 |
-29:34:36.2 |
HIP 116453 |
22.16 |
| 2026-10-02 12:00 |
23:36:08.51 |
-29:35:07.3 |
HIP 116453 |
21.30 |
| 2026-10-03 00:00 |
23:36:01.47 |
-29:35:37.8 |
HIP 116453 |
20.54 |
| 2026-10-03 12:00 |
23:35:54.46 |
-29:36:07.9 |
HIP 116453 |
19.90 |
| 2026-10-04 00:00 |
23:35:47.46 |
-29:36:37.5 |
HIP 116453 |
19.37 |
| 2026-10-04 12:00 |
23:35:40.48 |
-29:37:06.6 |
HIP 116453 |
18.98 |
| 2026-10-05 00:00 |
23:35:33.53 |
-29:37:35.2 |
HIP 116453 |
18.71 |
| 2026-10-05 12:00 |
23:35:26.59 |
-29:38:03.3 |
HIP 116453 |
18.59 |
| 2026-10-06 00:00 |
23:35:19.68 |
-29:38:30.9 |
HIP 116453 |
18.60 |
| 2026-10-06 12:00 |
23:35:12.79 |
-29:38:58.0 |
HIP 116453 |
18.75 |
| 2026-10-07 00:00 |
23:35:05.93 |
-29:39:24.6 |
HIP 116453 |
19.04 |
| 2026-10-07 12:00 |
23:34:59.09 |
-29:39:50.7 |
HIP 116453 |
19.44 |
| 2026-10-08 00:00 |
23:34:52.27 |
-29:40:16.3 |
HIP 116453 |
19.97 |
| 2026-10-08 12:00 |
23:34:45.48 |
-29:40:41.4 |
HIP 116453 |
20.59 |
| 2026-10-09 00:00 |
23:34:38.72 |
-29:41:06.1 |
HIP 116453 |
21.31 |
| 2026-10-09 12:00 |
23:34:31.98 |
-29:41:30.2 |
HIP 116453 |
22.12 |
| 2026-10-10 00:00 |
23:34:25.27 |
-29:41:53.8 |
HIP 116453 |
22.99 |
| 2026-10-10 12:00 |
23:34:18.59 |
-29:42:16.9 |
HIP 116453 |
23.93 |
| 2026-10-11 00:00 |
23:34:11.93 |
-29:42:39.5 |
HIP 116453 |
24.92 |