| Parameter |
Value |
| Designation |
C/2017 T3 (ATLAS) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2018-07-19T03:33:40.913280Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:33:37Z |
| Obs used |
542 |
| NEO |
- |
| M1 |
11.100 |
| K1 |
7.250 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2017-12-26.0000000 |
| e |
0.99938609 |
| q (au) |
0.825222 |
| a (au) |
1344.198875 |
| i (deg) |
88.107202 |
| Ω (om, deg) |
230.086754 |
| ω (w, deg) |
246.893600 |
| M (ma, deg) |
359.995897 |
Magnitude
Scatter + Global Linear
$$
M_a = (8.810 + 4.560\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
8.810 |
| n |
4.560 |
| gf |
0.999 |
| gb |
-1.000 |
| k |
0.996 |
| δ90 |
10.000 |
| 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 |
| 2017-09-11 |
2018-02-06 |
-0.7566 |
+0.403 |
| 2018-02-06 |
2018-03-16 |
-3.9246 |
+1.642 |
| 2018-03-16 |
2018-04-07 |
-11.8318 |
+4.242 |
| 2018-04-07 |
2018-07-18 |
+4.1330 |
-0.327 |
| 2018-07-19 |
2019-02-28 |
+4.6236 |
+0.173 |
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 |
16:13:40.04 |
+25:04:43.6 |
HIP 79510 |
10.09 |
| 2026-03-26 12:00 |
16:13:37.06 |
+25:05:48.0 |
HIP 79510 |
8.89 |
| 2026-03-27 00:00 |
16:13:34.03 |
+25:06:52.1 |
HIP 79510 |
7.71 |
| 2026-03-27 12:00 |
16:13:30.95 |
+25:07:56.1 |
HIP 79510 |
6.57 |
| 2026-03-28 00:00 |
16:13:27.83 |
+25:08:59.9 |
HIP 79510 |
5.49 |
| 2026-03-28 12:00 |
16:13:24.66 |
+25:10:03.5 |
HIP 79510 |
4.52 |
| 2026-03-29 00:00 |
16:13:21.44 |
+25:11:06.8 |
HIP 79510 |
3.74 |
| 2026-03-29 12:00 |
16:13:18.18 |
+25:12:10.0 |
HIP 79510 |
3.32 |
| 2026-03-30 00:00 |
16:13:14.87 |
+25:13:13.0 |
HIP 79510 |
3.37 |
| 2026-03-30 12:00 |
16:13:11.51 |
+25:14:15.7 |
HIP 79510 |
3.89 |
| 2026-03-31 00:00 |
16:13:08.11 |
+25:15:18.2 |
HIP 79510 |
4.72 |
| 2026-03-31 12:00 |
16:13:04.66 |
+25:16:20.5 |
HIP 79510 |
5.74 |
| 2026-04-01 00:00 |
16:13:01.17 |
+25:17:22.6 |
HIP 79510 |
6.86 |
| 2026-04-01 12:00 |
16:12:57.63 |
+25:18:24.4 |
HIP 79510 |
8.04 |
| 2026-04-02 00:00 |
16:12:54.04 |
+25:19:26.0 |
HIP 79510 |
9.26 |
| 2026-04-02 12:00 |
16:12:50.42 |
+25:20:27.3 |
HIP 79510 |
10.51 |
| 2026-04-03 00:00 |
16:12:46.75 |
+25:21:28.4 |
HIP 79510 |
11.78 |
| 2026-04-03 12:00 |
16:12:43.03 |
+25:22:29.3 |
HIP 79510 |
13.06 |
| 2026-04-04 00:00 |
16:12:39.27 |
+25:23:29.9 |
HIP 79510 |
14.35 |
| 2026-04-04 12:00 |
16:12:35.47 |
+25:24:30.2 |
HIP 79510 |
15.65 |
| 2026-04-05 00:00 |
16:12:31.62 |
+25:25:30.2 |
HIP 79510 |
16.96 |
| 2026-04-05 12:00 |
16:12:27.73 |
+25:26:30.0 |
HIP 79510 |
18.28 |
| 2026-04-06 00:00 |
16:12:23.80 |
+25:27:29.6 |
HIP 79510 |
19.60 |
| 2026-04-06 12:00 |
16:12:19.83 |
+25:28:28.8 |
HIP 79510 |
20.93 |
| 2026-04-07 00:00 |
16:12:15.81 |
+25:29:27.7 |
HIP 79510 |
22.26 |
| 2026-04-07 12:00 |
16:12:11.75 |
+25:30:26.4 |
HIP 79510 |
23.59 |
| 2026-04-08 00:00 |
16:12:07.65 |
+25:31:24.8 |
HIP 79510 |
24.93 |
| 2026-04-08 12:00 |
16:12:03.51 |
+25:32:22.9 |
HIP 79510 |
26.27 |
| 2026-04-09 00:00 |
16:11:59.33 |
+25:33:20.6 |
HIP 79225 |
25.79 |
| 2026-04-09 12:00 |
16:11:55.11 |
+25:34:18.1 |
HIP 79225 |
25.02 |
| 2026-04-10 00:00 |
16:11:50.85 |
+25:35:15.2 |
HIP 79225 |
24.29 |
| 2026-04-10 12:00 |
16:11:46.55 |
+25:36:12.1 |
HIP 79225 |
23.61 |
| 2026-04-11 00:00 |
16:11:42.21 |
+25:37:08.6 |
HIP 79225 |
22.98 |
| 2026-04-11 12:00 |
16:11:37.83 |
+25:38:04.8 |
HIP 79225 |
22.41 |
| 2026-04-12 00:00 |
16:11:33.41 |
+25:39:00.7 |
HIP 79225 |
21.89 |
| 2026-04-12 12:00 |
16:11:28.95 |
+25:39:56.2 |
HIP 79225 |
21.44 |
| 2026-04-13 00:00 |
16:11:24.46 |
+25:40:51.4 |
HIP 79225 |
21.06 |
| 2026-04-13 12:00 |
16:11:19.93 |
+25:41:46.2 |
HIP 79225 |
20.75 |
| 2026-04-14 00:00 |
16:11:15.36 |
+25:42:40.8 |
HIP 79225 |
20.52 |
| 2026-04-14 12:00 |
16:11:10.75 |
+25:43:34.9 |
HIP 79225 |
20.37 |
| 2026-04-15 00:00 |
16:11:06.11 |
+25:44:28.7 |
HIP 79225 |
20.30 |
| 2026-04-15 12:00 |
16:11:01.43 |
+25:45:22.1 |
HIP 79225 |
20.32 |
| 2026-04-16 00:00 |
16:10:56.71 |
+25:46:15.2 |
HIP 79225 |
20.42 |