| 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) |
| 2026-07-29 00:00 |
23:50:38.98 |
-27:35:54.6 |
HIP 117481 |
23.32 |
| 2026-07-29 12:00 |
23:50:34.22 |
-27:37:01.7 |
HIP 117481 |
21.80 |
| 2026-07-30 00:00 |
23:50:29.41 |
-27:38:08.7 |
HIP 117481 |
20.26 |
| 2026-07-30 12:00 |
23:50:24.55 |
-27:39:15.8 |
HIP 117481 |
18.72 |
| 2026-07-31 00:00 |
23:50:19.65 |
-27:40:22.9 |
HIP 117481 |
17.17 |
| 2026-07-31 12:00 |
23:50:14.70 |
-27:41:30.0 |
HIP 117481 |
15.61 |
| 2026-08-01 00:00 |
23:50:09.71 |
-27:42:37.0 |
HIP 117481 |
14.05 |
| 2026-08-01 12:00 |
23:50:04.67 |
-27:43:44.1 |
HIP 117481 |
12.49 |
| 2026-08-02 00:00 |
23:49:59.58 |
-27:44:51.1 |
HIP 117481 |
10.92 |
| 2026-08-02 12:00 |
23:49:54.45 |
-27:45:58.1 |
HIP 117481 |
9.35 |
| 2026-08-03 00:00 |
23:49:49.27 |
-27:47:05.1 |
HIP 117481 |
7.78 |
| 2026-08-03 12:00 |
23:49:44.05 |
-27:48:12.0 |
HIP 117481 |
6.21 |
| 2026-08-04 00:00 |
23:49:38.79 |
-27:49:18.9 |
HIP 117481 |
4.67 |
| 2026-08-04 12:00 |
23:49:33.48 |
-27:50:25.8 |
HIP 117481 |
3.18 |
| 2026-08-05 00:00 |
23:49:28.13 |
-27:51:32.6 |
HIP 117481 |
1.91 |
| 2026-08-05 12:00 |
23:49:22.74 |
-27:52:39.3 |
HIP 117481 |
1.57 |
| 2026-08-06 00:00 |
23:49:17.30 |
-27:53:46.0 |
HIP 117481 |
2.57 |
| 2026-08-06 12:00 |
23:49:11.82 |
-27:54:52.6 |
HIP 117481 |
4.01 |
| 2026-08-07 00:00 |
23:49:06.29 |
-27:55:59.2 |
HIP 117481 |
5.57 |
| 2026-08-07 12:00 |
23:49:00.73 |
-27:57:05.7 |
HIP 117481 |
7.18 |
| 2026-08-08 00:00 |
23:48:55.12 |
-27:58:12.1 |
HIP 117404 |
8.67 |
| 2026-08-08 12:00 |
23:48:49.48 |
-27:59:18.4 |
HIP 117404 |
8.30 |
| 2026-08-09 00:00 |
23:48:43.79 |
-28:00:24.7 |
HIP 117452 |
7.83 |
| 2026-08-09 12:00 |
23:48:38.06 |
-28:01:30.8 |
HIP 117452 |
7.37 |
| 2026-08-10 00:00 |
23:48:32.29 |
-28:02:36.9 |
HIP 117452 |
7.28 |
| 2026-08-10 12:00 |
23:48:26.48 |
-28:03:42.8 |
HIP 117452 |
7.59 |
| 2026-08-11 00:00 |
23:48:20.63 |
-28:04:48.7 |
HIP 117452 |
8.25 |
| 2026-08-11 12:00 |
23:48:14.75 |
-28:05:54.4 |
HIP 117452 |
9.18 |
| 2026-08-12 00:00 |
23:48:08.82 |
-28:07:00.0 |
HIP 117452 |
10.32 |
| 2026-08-12 12:00 |
23:48:02.86 |
-28:08:05.5 |
HIP 117452 |
11.60 |
| 2026-08-13 00:00 |
23:47:56.86 |
-28:09:10.8 |
HIP 117343 |
10.54 |
| 2026-08-13 12:00 |
23:47:50.82 |
-28:10:16.0 |
HIP 117343 |
9.01 |
| 2026-08-14 00:00 |
23:47:44.75 |
-28:11:21.1 |
HIP 117343 |
7.56 |
| 2026-08-14 12:00 |
23:47:38.63 |
-28:12:26.0 |
HIP 117343 |
6.24 |
| 2026-08-15 00:00 |
23:47:32.49 |
-28:13:30.8 |
HIP 117343 |
5.18 |
| 2026-08-15 12:00 |
23:47:26.31 |
-28:14:35.4 |
HIP 117343 |
4.56 |
| 2026-08-16 00:00 |
23:47:20.09 |
-28:15:39.9 |
HIP 117343 |
4.56 |
| 2026-08-16 12:00 |
23:47:13.84 |
-28:16:44.2 |
HIP 117343 |
5.19 |
| 2026-08-17 00:00 |
23:47:07.56 |
-28:17:48.3 |
HIP 117343 |
6.26 |
| 2026-08-17 12:00 |
23:47:01.24 |
-28:18:52.3 |
HIP 117343 |
7.60 |
| 2026-08-18 00:00 |
23:46:54.89 |
-28:19:56.0 |
HIP 117343 |
9.09 |
| 2026-08-18 12:00 |
23:46:48.51 |
-28:20:59.6 |
HIP 117343 |
10.66 |
| 2026-08-19 00:00 |
23:46:42.09 |
-28:22:03.0 |
HIP 117343 |
12.29 |