| 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) |
| 2026-07-29 00:00 |
15:53:29.23 |
+25:53:39.9 |
HIP 77841 |
6.77 |
| 2026-07-29 12:00 |
15:53:26.98 |
+25:52:55.5 |
HIP 77841 |
6.28 |
| 2026-07-30 00:00 |
15:53:24.79 |
+25:52:11.0 |
HIP 77841 |
5.87 |
| 2026-07-30 12:00 |
15:53:22.64 |
+25:51:26.1 |
HIP 77841 |
5.56 |
| 2026-07-31 00:00 |
15:53:20.54 |
+25:50:41.1 |
HIP 77841 |
5.37 |
| 2026-07-31 12:00 |
15:53:18.48 |
+25:49:55.7 |
HIP 77841 |
5.32 |
| 2026-08-01 00:00 |
15:53:16.48 |
+25:49:10.1 |
HIP 77841 |
5.40 |
| 2026-08-01 12:00 |
15:53:14.52 |
+25:48:24.3 |
HIP 77841 |
5.61 |
| 2026-08-02 00:00 |
15:53:12.61 |
+25:47:38.2 |
HIP 77841 |
5.93 |
| 2026-08-02 12:00 |
15:53:10.75 |
+25:46:51.9 |
HIP 77841 |
6.35 |
| 2026-08-03 00:00 |
15:53:08.94 |
+25:46:05.4 |
HIP 77841 |
6.85 |
| 2026-08-03 12:00 |
15:53:07.17 |
+25:45:18.6 |
HIP 77841 |
7.41 |
| 2026-08-04 00:00 |
15:53:05.45 |
+25:44:31.6 |
HIP 77841 |
8.01 |
| 2026-08-04 12:00 |
15:53:03.78 |
+25:43:44.4 |
HIP 77841 |
8.66 |
| 2026-08-05 00:00 |
15:53:02.16 |
+25:42:57.0 |
HIP 77841 |
9.33 |
| 2026-08-05 12:00 |
15:53:00.59 |
+25:42:09.4 |
HIP 77841 |
10.02 |
| 2026-08-06 00:00 |
15:52:59.07 |
+25:41:21.5 |
HIP 77841 |
10.74 |
| 2026-08-06 12:00 |
15:52:57.59 |
+25:40:33.5 |
HIP 77841 |
11.47 |
| 2026-08-07 00:00 |
15:52:56.17 |
+25:39:45.2 |
HIP 77841 |
12.21 |
| 2026-08-07 12:00 |
15:52:54.79 |
+25:38:56.7 |
HIP 77841 |
12.95 |
| 2026-08-08 00:00 |
15:52:53.46 |
+25:38:08.1 |
HIP 77841 |
13.71 |
| 2026-08-08 12:00 |
15:52:52.18 |
+25:37:19.2 |
HIP 77841 |
14.47 |
| 2026-08-09 00:00 |
15:52:50.95 |
+25:36:30.2 |
HIP 77841 |
15.24 |
| 2026-08-09 12:00 |
15:52:49.77 |
+25:35:41.0 |
HIP 77841 |
16.01 |
| 2026-08-10 00:00 |
15:52:48.64 |
+25:34:51.6 |
HIP 77841 |
16.79 |
| 2026-08-10 12:00 |
15:52:47.56 |
+25:34:02.0 |
HIP 77841 |
17.57 |
| 2026-08-11 00:00 |
15:52:46.53 |
+25:33:12.3 |
HIP 77841 |
18.35 |
| 2026-08-11 12:00 |
15:52:45.55 |
+25:32:22.4 |
HIP 77841 |
19.13 |
| 2026-08-12 00:00 |
15:52:44.61 |
+25:31:32.3 |
HIP 77841 |
19.92 |
| 2026-08-12 12:00 |
15:52:43.73 |
+25:30:42.1 |
HIP 77841 |
20.71 |
| 2026-08-13 00:00 |
15:52:42.89 |
+25:29:51.7 |
HIP 77676 |
20.27 |
| 2026-08-13 12:00 |
15:52:42.11 |
+25:29:01.2 |
HIP 77676 |
19.65 |
| 2026-08-14 00:00 |
15:52:41.37 |
+25:28:10.5 |
HIP 77676 |
19.06 |
| 2026-08-14 12:00 |
15:52:40.69 |
+25:27:19.7 |
HIP 77676 |
18.49 |
| 2026-08-15 00:00 |
15:52:40.05 |
+25:26:28.8 |
HIP 77676 |
17.97 |
| 2026-08-15 12:00 |
15:52:39.47 |
+25:25:37.7 |
HIP 77676 |
17.47 |
| 2026-08-16 00:00 |
15:52:38.93 |
+25:24:46.5 |
HIP 77676 |
17.02 |
| 2026-08-16 12:00 |
15:52:38.44 |
+25:23:55.2 |
HIP 77676 |
16.61 |
| 2026-08-17 00:00 |
15:52:38.00 |
+25:23:03.7 |
HIP 77676 |
16.24 |
| 2026-08-17 12:00 |
15:52:37.61 |
+25:22:12.2 |
HIP 77676 |
15.92 |
| 2026-08-18 00:00 |
15:52:37.28 |
+25:21:20.5 |
HIP 77676 |
15.66 |
| 2026-08-18 12:00 |
15:52:36.99 |
+25:20:28.8 |
HIP 77676 |
15.45 |
| 2026-08-19 00:00 |
15:52:36.75 |
+25:19:36.9 |
HIP 77676 |
15.29 |