| 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
$$
M_a = (10.483 + 3.261\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
10.483 |
| n |
3.261 |
| gf |
0.999 |
| gb |
-0.500 |
| k |
0.800 |
| δ90 |
3.469 |
| 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 |
+4.9810 |
-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) |
| 2026-03-26 00:00 |
23:44:42.62 |
-25:21:06.2 |
HIP 117019 |
18.42 |
| 2026-03-26 12:00 |
23:44:48.39 |
-25:20:50.2 |
HIP 117139 |
18.62 |
| 2026-03-27 00:00 |
23:44:54.15 |
-25:20:34.6 |
HIP 117139 |
18.89 |
| 2026-03-27 12:00 |
23:44:59.90 |
-25:20:19.3 |
HIP 117139 |
19.24 |
| 2026-03-28 00:00 |
23:45:05.63 |
-25:20:04.3 |
HIP 117139 |
19.66 |
| 2026-03-28 12:00 |
23:45:11.36 |
-25:19:49.8 |
HIP 117139 |
20.16 |
| 2026-03-29 00:00 |
23:45:17.08 |
-25:19:35.6 |
HIP 117139 |
20.72 |
| 2026-03-29 12:00 |
23:45:22.78 |
-25:19:21.8 |
HIP 117139 |
21.35 |
| 2026-03-30 00:00 |
23:45:28.47 |
-25:19:08.3 |
HIP 117139 |
22.02 |
| 2026-03-30 12:00 |
23:45:34.15 |
-25:18:55.2 |
HIP 117139 |
22.74 |
| 2026-03-31 00:00 |
23:45:39.82 |
-25:18:42.4 |
HIP 117139 |
23.51 |
| 2026-03-31 12:00 |
23:45:45.48 |
-25:18:30.1 |
HIP 117139 |
24.32 |
| 2026-04-01 00:00 |
23:45:51.12 |
-25:18:18.1 |
HIP 117139 |
25.15 |
| 2026-04-01 12:00 |
23:45:56.75 |
-25:18:06.5 |
HIP 117139 |
26.02 |
| 2026-04-02 00:00 |
23:46:02.36 |
-25:17:55.2 |
HIP 117139 |
26.92 |
| 2026-04-02 12:00 |
23:46:07.96 |
-25:17:44.3 |
HIP 117139 |
27.84 |
| 2026-04-03 00:00 |
23:46:13.54 |
-25:17:33.8 |
HIP 117139 |
28.77 |
| 2026-04-03 12:00 |
23:46:19.11 |
-25:17:23.7 |
HIP 117139 |
29.73 |
| 2026-04-04 00:00 |
23:46:24.66 |
-25:17:14.0 |
HIP 117139 |
30.70 |
| 2026-04-04 12:00 |
23:46:30.20 |
-25:17:04.6 |
HIP 117139 |
31.69 |
| 2026-04-05 00:00 |
23:46:35.72 |
-25:16:55.6 |
HIP 117139 |
32.69 |
| 2026-04-05 12:00 |
23:46:41.23 |
-25:16:47.0 |
HIP 117454 |
31.75 |
| 2026-04-06 00:00 |
23:46:46.71 |
-25:16:38.8 |
HIP 117454 |
30.51 |
| 2026-04-06 12:00 |
23:46:52.18 |
-25:16:31.0 |
HIP 117454 |
29.29 |
| 2026-04-07 00:00 |
23:46:57.64 |
-25:16:23.6 |
HIP 117454 |
28.07 |
| 2026-04-07 12:00 |
23:47:03.07 |
-25:16:16.5 |
HIP 117454 |
26.85 |
| 2026-04-08 00:00 |
23:47:08.49 |
-25:16:09.9 |
HIP 117454 |
25.65 |
| 2026-04-08 12:00 |
23:47:13.88 |
-25:16:03.6 |
HIP 117454 |
24.45 |
| 2026-04-09 00:00 |
23:47:19.26 |
-25:15:57.8 |
HIP 117454 |
23.27 |
| 2026-04-09 12:00 |
23:47:24.62 |
-25:15:52.3 |
HIP 117454 |
22.09 |
| 2026-04-10 00:00 |
23:47:29.96 |
-25:15:47.2 |
HIP 117454 |
20.92 |
| 2026-04-10 12:00 |
23:47:35.28 |
-25:15:42.6 |
HIP 117454 |
19.77 |
| 2026-04-11 00:00 |
23:47:40.58 |
-25:15:38.3 |
HIP 117454 |
18.62 |
| 2026-04-11 12:00 |
23:47:45.85 |
-25:15:34.5 |
HIP 117454 |
17.50 |
| 2026-04-12 00:00 |
23:47:51.11 |
-25:15:31.0 |
HIP 117454 |
16.39 |
| 2026-04-12 12:00 |
23:47:56.34 |
-25:15:27.9 |
HIP 117454 |
15.30 |
| 2026-04-13 00:00 |
23:48:01.55 |
-25:15:25.3 |
HIP 117454 |
14.23 |
| 2026-04-13 12:00 |
23:48:06.74 |
-25:15:23.1 |
HIP 117454 |
13.19 |
| 2026-04-14 00:00 |
23:48:11.91 |
-25:15:21.2 |
HIP 117454 |
12.18 |
| 2026-04-14 12:00 |
23:48:17.05 |
-25:15:19.8 |
HIP 117454 |
11.21 |
| 2026-04-15 00:00 |
23:48:22.17 |
-25:15:18.8 |
HIP 117454 |
10.29 |
| 2026-04-15 12:00 |
23:48:27.27 |
-25:15:18.2 |
HIP 117454 |
9.43 |
| 2026-04-16 00:00 |
23:48:32.34 |
-25:15:18.0 |
HIP 117454 |
8.65 |