| 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 |
-0.7569 |
+0.403 |
| 2018-02-06 |
2018-03-16 |
-3.9243 |
+1.642 |
| 2018-03-16 |
2018-04-07 |
-11.8310 |
+4.241 |
| 2018-04-07 |
2018-07-18 |
+4.1328 |
-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) |
| 2026-09-20 00:00 |
15:53:59.84 |
+24:23:48.2 |
HIP 77935 |
17.98 |
| 2026-09-20 12:00 |
15:54:02.59 |
+24:22:58.2 |
HIP 77935 |
18.13 |
| 2026-09-21 00:00 |
15:54:05.38 |
+24:22:08.3 |
HIP 77935 |
18.33 |
| 2026-09-21 12:00 |
15:54:08.21 |
+24:21:18.6 |
HIP 77935 |
18.57 |
| 2026-09-22 00:00 |
15:54:11.08 |
+24:20:29.0 |
HIP 77935 |
18.87 |
| 2026-09-22 12:00 |
15:54:13.99 |
+24:19:39.7 |
HIP 77935 |
19.21 |
| 2026-09-23 00:00 |
15:54:16.94 |
+24:18:50.4 |
HIP 77935 |
19.59 |
| 2026-09-23 12:00 |
15:54:19.93 |
+24:18:01.4 |
HIP 77935 |
20.02 |
| 2026-09-24 00:00 |
15:54:22.96 |
+24:17:12.5 |
HIP 77935 |
20.49 |
| 2026-09-24 12:00 |
15:54:26.03 |
+24:16:23.8 |
HIP 77935 |
20.99 |
| 2026-09-25 00:00 |
15:54:29.13 |
+24:15:35.3 |
HIP 77935 |
21.53 |
| 2026-09-25 12:00 |
15:54:32.28 |
+24:14:47.0 |
HIP 77935 |
22.11 |
| 2026-09-26 00:00 |
15:54:35.46 |
+24:13:58.9 |
HIP 77935 |
22.71 |
| 2026-09-26 12:00 |
15:54:38.68 |
+24:13:10.9 |
HIP 77935 |
23.35 |
| 2026-09-27 00:00 |
15:54:41.94 |
+24:12:23.2 |
HIP 77935 |
24.01 |
| 2026-09-27 12:00 |
15:54:45.24 |
+24:11:35.6 |
HIP 78068 |
24.40 |
| 2026-09-28 00:00 |
15:54:48.58 |
+24:10:48.2 |
HIP 78068 |
24.02 |
| 2026-09-28 12:00 |
15:54:51.95 |
+24:10:01.1 |
HIP 78068 |
23.68 |
| 2026-09-29 00:00 |
15:54:55.36 |
+24:09:14.1 |
HIP 78068 |
23.37 |
| 2026-09-29 12:00 |
15:54:58.80 |
+24:08:27.4 |
HIP 78068 |
23.10 |
| 2026-09-30 00:00 |
15:55:02.28 |
+24:07:40.8 |
HIP 78068 |
22.88 |
| 2026-09-30 12:00 |
15:55:05.80 |
+24:06:54.5 |
HIP 78068 |
22.69 |
| 2026-10-01 00:00 |
15:55:09.36 |
+24:06:08.4 |
HIP 78068 |
22.55 |
| 2026-10-01 12:00 |
15:55:12.95 |
+24:05:22.5 |
HIP 78068 |
22.46 |
| 2026-10-02 00:00 |
15:55:16.57 |
+24:04:36.8 |
HIP 78068 |
22.42 |
| 2026-10-02 12:00 |
15:55:20.24 |
+24:03:51.4 |
HIP 78068 |
22.42 |
| 2026-10-03 00:00 |
15:55:23.93 |
+24:03:06.2 |
HIP 78068 |
22.47 |
| 2026-10-03 12:00 |
15:55:27.67 |
+24:02:21.2 |
HIP 78068 |
22.57 |
| 2026-10-04 00:00 |
15:55:31.43 |
+24:01:36.5 |
HIP 78068 |
22.72 |
| 2026-10-04 12:00 |
15:55:35.23 |
+24:00:52.0 |
HIP 78068 |
22.92 |
| 2026-10-05 00:00 |
15:55:39.07 |
+24:00:07.7 |
HIP 78068 |
23.17 |
| 2026-10-05 12:00 |
15:55:42.94 |
+23:59:23.7 |
HIP 78068 |
23.46 |
| 2026-10-06 00:00 |
15:55:46.84 |
+23:58:39.9 |
HIP 78068 |
23.79 |
| 2026-10-06 12:00 |
15:55:50.78 |
+23:57:56.4 |
HIP 78068 |
24.17 |
| 2026-10-07 00:00 |
15:55:54.75 |
+23:57:13.2 |
HIP 78068 |
24.59 |
| 2026-10-07 12:00 |
15:55:58.75 |
+23:56:30.2 |
HIP 78068 |
25.06 |
| 2026-10-08 00:00 |
15:56:02.79 |
+23:55:47.5 |
HIP 78068 |
25.56 |
| 2026-10-08 12:00 |
15:56:06.86 |
+23:55:05.0 |
HIP 78068 |
26.10 |
| 2026-10-09 00:00 |
15:56:10.96 |
+23:54:22.8 |
HIP 78022 |
26.02 |
| 2026-10-09 12:00 |
15:56:15.09 |
+23:53:40.9 |
HIP 78022 |
25.50 |
| 2026-10-10 00:00 |
15:56:19.26 |
+23:52:59.3 |
HIP 78022 |
25.02 |
| 2026-10-10 12:00 |
15:56:23.45 |
+23:52:17.9 |
HIP 78022 |
24.61 |
| 2026-10-11 00:00 |
15:56:27.68 |
+23:51:36.8 |
HIP 78022 |
24.25 |