| 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) |
| 2026-07-29 00:00 |
06:47:11.31 |
+28:33:13.5 |
HIP 32700 |
28.12 |
| 2026-07-29 12:00 |
06:47:18.00 |
+28:33:07.2 |
HIP 32700 |
26.65 |
| 2026-07-30 00:00 |
06:47:24.66 |
+28:33:01.0 |
HIP 32700 |
25.19 |
| 2026-07-30 12:00 |
06:47:31.30 |
+28:32:54.8 |
HIP 32700 |
23.73 |
| 2026-07-31 00:00 |
06:47:37.92 |
+28:32:48.7 |
HIP 32700 |
22.27 |
| 2026-07-31 12:00 |
06:47:44.51 |
+28:32:42.7 |
HIP 32700 |
20.82 |
| 2026-08-01 00:00 |
06:47:51.08 |
+28:32:36.8 |
HIP 32700 |
19.38 |
| 2026-08-01 12:00 |
06:47:57.63 |
+28:32:30.9 |
HIP 32700 |
17.94 |
| 2026-08-02 00:00 |
06:48:04.14 |
+28:32:25.1 |
HIP 32700 |
16.51 |
| 2026-08-02 12:00 |
06:48:10.64 |
+28:32:19.3 |
HIP 32700 |
15.09 |
| 2026-08-03 00:00 |
06:48:17.11 |
+28:32:13.6 |
HIP 32700 |
13.67 |
| 2026-08-03 12:00 |
06:48:23.55 |
+28:32:08.0 |
HIP 32700 |
12.25 |
| 2026-08-04 00:00 |
06:48:29.97 |
+28:32:02.5 |
HIP 32700 |
10.85 |
| 2026-08-04 12:00 |
06:48:36.36 |
+28:31:57.1 |
HIP 32700 |
9.45 |
| 2026-08-05 00:00 |
06:48:42.72 |
+28:31:51.7 |
HIP 32700 |
8.06 |
| 2026-08-05 12:00 |
06:48:49.06 |
+28:31:46.4 |
HIP 32700 |
6.69 |
| 2026-08-06 00:00 |
06:48:55.37 |
+28:31:41.1 |
HIP 32700 |
5.33 |
| 2026-08-06 12:00 |
06:49:01.65 |
+28:31:36.0 |
HIP 32700 |
3.99 |
| 2026-08-07 00:00 |
06:49:07.90 |
+28:31:30.9 |
HIP 32700 |
2.70 |
| 2026-08-07 12:00 |
06:49:14.12 |
+28:31:25.9 |
HIP 32700 |
1.57 |
| 2026-08-08 00:00 |
06:49:20.32 |
+28:31:20.9 |
HIP 32700 |
1.18 |
| 2026-08-08 12:00 |
06:49:26.48 |
+28:31:16.1 |
HIP 32700 |
2.00 |
| 2026-08-09 00:00 |
06:49:32.62 |
+28:31:11.3 |
HIP 32700 |
3.20 |
| 2026-08-09 12:00 |
06:49:38.72 |
+28:31:06.6 |
HIP 32700 |
4.48 |
| 2026-08-10 00:00 |
06:49:44.79 |
+28:31:02.0 |
HIP 32700 |
5.79 |
| 2026-08-10 12:00 |
06:49:50.84 |
+28:30:57.4 |
HIP 32700 |
7.09 |
| 2026-08-11 00:00 |
06:49:56.85 |
+28:30:52.9 |
HIP 32700 |
8.40 |
| 2026-08-11 12:00 |
06:50:02.83 |
+28:30:48.5 |
HIP 32700 |
9.71 |
| 2026-08-12 00:00 |
06:50:08.77 |
+28:30:44.2 |
HIP 32700 |
11.01 |
| 2026-08-12 12:00 |
06:50:14.69 |
+28:30:40.0 |
HIP 32700 |
12.30 |
| 2026-08-13 00:00 |
06:50:20.57 |
+28:30:35.8 |
HIP 32700 |
13.59 |
| 2026-08-13 12:00 |
06:50:26.42 |
+28:30:31.8 |
HIP 32700 |
14.87 |
| 2026-08-14 00:00 |
06:50:32.23 |
+28:30:27.8 |
HIP 32737 |
15.99 |
| 2026-08-14 12:00 |
06:50:38.01 |
+28:30:23.9 |
HIP 32737 |
16.86 |
| 2026-08-15 00:00 |
06:50:43.76 |
+28:30:20.0 |
HIP 32737 |
17.78 |
| 2026-08-15 12:00 |
06:50:49.47 |
+28:30:16.3 |
HIP 32737 |
18.73 |
| 2026-08-16 00:00 |
06:50:55.14 |
+28:30:12.6 |
HIP 32737 |
19.71 |
| 2026-08-16 12:00 |
06:51:00.78 |
+28:30:09.0 |
HIP 32737 |
20.71 |
| 2026-08-17 00:00 |
06:51:06.39 |
+28:30:05.5 |
HIP 32737 |
21.73 |
| 2026-08-17 12:00 |
06:51:11.96 |
+28:30:02.1 |
HIP 32737 |
22.77 |
| 2026-08-18 00:00 |
06:51:17.49 |
+28:29:58.8 |
HIP 32737 |
23.82 |
| 2026-08-18 12:00 |
06:51:22.98 |
+28:29:55.5 |
HIP 32737 |
24.87 |
| 2026-08-19 00:00 |
06:51:28.44 |
+28:29:52.3 |
HIP 33053 |
24.99 |