| Parameter |
Value |
| Designation |
C/2017 K4 (ATLAS) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2018-01-08T01:00:52.058880Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:33:33Z |
| Obs used |
556 |
| NEO |
- |
| M1 |
4.700 |
| K1 |
19.500 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2018-03-28.0000000 |
| e |
0.90585450 |
| q (au) |
2.648085 |
| a (au) |
28.127579 |
| i (deg) |
16.678706 |
| Ω (om, deg) |
298.897270 |
| ω (w, deg) |
15.111911 |
| M (ma, deg) |
0.521675 |
Magnitude
Scatter + Global Linear
$$
M_a = (6.069 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
6.069 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-1.000 |
| k |
1.000 |
| 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 |
| 2016-05-06 |
2017-11-12 |
+3.1769 |
-1.847 |
| 2018-04-27 |
2019-01-27 |
-4.4170 |
+2.873 |
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 |
06:23:53.99 |
+29:21:20.1 |
HIP 30561 |
24.07 |
| 2026-03-26 12:00 |
06:23:54.78 |
+29:21:06.5 |
HIP 30561 |
24.05 |
| 2026-03-27 00:00 |
06:23:55.63 |
+29:20:52.9 |
HIP 30561 |
24.02 |
| 2026-03-27 12:00 |
06:23:56.55 |
+29:20:39.3 |
HIP 30561 |
23.98 |
| 2026-03-28 00:00 |
06:23:57.53 |
+29:20:25.7 |
HIP 30561 |
23.94 |
| 2026-03-28 12:00 |
06:23:58.56 |
+29:20:12.1 |
HIP 30561 |
23.88 |
| 2026-03-29 00:00 |
06:23:59.66 |
+29:19:58.5 |
HIP 30561 |
23.83 |
| 2026-03-29 12:00 |
06:24:00.83 |
+29:19:44.8 |
HIP 30561 |
23.76 |
| 2026-03-30 00:00 |
06:24:02.05 |
+29:19:31.1 |
HIP 30561 |
23.70 |
| 2026-03-30 12:00 |
06:24:03.33 |
+29:19:17.4 |
HIP 30561 |
23.62 |
| 2026-03-31 00:00 |
06:24:04.67 |
+29:19:03.7 |
HIP 30561 |
23.54 |
| 2026-03-31 12:00 |
06:24:06.08 |
+29:18:50.0 |
HIP 30561 |
23.46 |
| 2026-04-01 00:00 |
06:24:07.54 |
+29:18:36.3 |
HIP 30561 |
23.38 |
| 2026-04-01 12:00 |
06:24:09.07 |
+29:18:22.6 |
HIP 30561 |
23.29 |
| 2026-04-02 00:00 |
06:24:10.65 |
+29:18:08.8 |
HIP 30561 |
23.19 |
| 2026-04-02 12:00 |
06:24:12.29 |
+29:17:55.0 |
HIP 30561 |
23.10 |
| 2026-04-03 00:00 |
06:24:14.00 |
+29:17:41.3 |
HIP 30561 |
23.01 |
| 2026-04-03 12:00 |
06:24:15.76 |
+29:17:27.5 |
HIP 30561 |
22.91 |
| 2026-04-04 00:00 |
06:24:17.58 |
+29:17:13.7 |
HIP 30561 |
22.81 |
| 2026-04-04 12:00 |
06:24:19.47 |
+29:17:00.0 |
HIP 30561 |
22.72 |
| 2026-04-05 00:00 |
06:24:21.41 |
+29:16:46.1 |
HIP 30561 |
22.62 |
| 2026-04-05 12:00 |
06:24:23.41 |
+29:16:32.3 |
HIP 30561 |
22.53 |
| 2026-04-06 00:00 |
06:24:25.46 |
+29:16:18.5 |
HIP 30561 |
22.44 |
| 2026-04-06 12:00 |
06:24:27.58 |
+29:16:04.7 |
HIP 30561 |
22.35 |
| 2026-04-07 00:00 |
06:24:29.75 |
+29:15:50.9 |
HIP 30561 |
22.27 |
| 2026-04-07 12:00 |
06:24:31.99 |
+29:15:37.1 |
HIP 30561 |
22.20 |
| 2026-04-08 00:00 |
06:24:34.28 |
+29:15:23.2 |
HIP 30561 |
22.13 |
| 2026-04-08 12:00 |
06:24:36.62 |
+29:15:09.4 |
HIP 30561 |
22.06 |
| 2026-04-09 00:00 |
06:24:39.03 |
+29:14:55.6 |
HIP 30561 |
22.01 |
| 2026-04-09 12:00 |
06:24:41.49 |
+29:14:41.7 |
HIP 30561 |
21.96 |
| 2026-04-10 00:00 |
06:24:44.01 |
+29:14:27.9 |
HIP 30561 |
21.93 |
| 2026-04-10 12:00 |
06:24:46.59 |
+29:14:14.1 |
HIP 30561 |
21.90 |
| 2026-04-11 00:00 |
06:24:49.22 |
+29:14:00.2 |
HIP 30561 |
21.89 |
| 2026-04-11 12:00 |
06:24:51.91 |
+29:13:46.4 |
HIP 30561 |
21.89 |
| 2026-04-12 00:00 |
06:24:54.65 |
+29:13:32.6 |
HIP 30561 |
21.91 |
| 2026-04-12 12:00 |
06:24:57.46 |
+29:13:18.7 |
HIP 30561 |
21.94 |
| 2026-04-13 00:00 |
06:25:00.31 |
+29:13:04.9 |
HIP 30561 |
21.99 |
| 2026-04-13 12:00 |
06:25:03.22 |
+29:12:51.0 |
HIP 30561 |
22.05 |
| 2026-04-14 00:00 |
06:25:06.19 |
+29:12:37.2 |
HIP 30561 |
22.13 |
| 2026-04-14 12:00 |
06:25:09.22 |
+29:12:23.4 |
HIP 30561 |
22.23 |
| 2026-04-15 00:00 |
06:25:12.29 |
+29:12:09.6 |
HIP 30561 |
22.35 |
| 2026-04-15 12:00 |
06:25:15.42 |
+29:11:55.7 |
HIP 30561 |
22.49 |
| 2026-04-16 00:00 |
06:25:18.61 |
+29:11:41.9 |
HIP 30561 |
22.65 |