| Parameter |
Value |
| Designation |
C/2015 X7 (ATLAS) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2016-07-30T05:59:33.682560Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:33:20Z |
| Obs used |
620 |
| NEO |
- |
| M1 |
11.600 |
| K1 |
6.000 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2016-09-22.0000000 |
| e |
1.00189036 |
| q (au) |
3.684550 |
| a (au) |
-1949.127032 |
| i (deg) |
57.578925 |
| Ω (om, deg) |
139.884070 |
| ω (w, deg) |
348.488537 |
| M (ma, deg) |
0.000616 |
Magnitude
Scatter + Global Linear
$$
M_a = (11.078 + 2.092\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
11.078 |
| n |
2.092 |
| gf |
1.000 |
| gb |
-0.502 |
| 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 |
| 2015-01-28 |
2016-05-01 |
-0.2726 |
-0.309 |
| 2016-11-02 |
2017-06-16 |
-0.5340 |
+0.555 |
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 |
18:19:21.05 |
+24:32:18.4 |
HIP 89773 |
6.03 |
| 2026-07-29 12:00 |
18:19:16.78 |
+24:31:40.4 |
HIP 89773 |
5.10 |
| 2026-07-30 00:00 |
18:19:12.54 |
+24:31:02.1 |
HIP 89773 |
4.29 |
| 2026-07-30 12:00 |
18:19:08.32 |
+24:30:23.3 |
HIP 89773 |
3.67 |
| 2026-07-31 00:00 |
18:19:04.14 |
+24:29:44.2 |
HIP 89773 |
3.32 |
| 2026-07-31 12:00 |
18:18:59.98 |
+24:29:04.6 |
HIP 89773 |
3.36 |
| 2026-08-01 00:00 |
18:18:55.85 |
+24:28:24.7 |
HIP 89773 |
3.75 |
| 2026-08-01 12:00 |
18:18:51.76 |
+24:27:44.4 |
HIP 89773 |
4.41 |
| 2026-08-02 00:00 |
18:18:47.69 |
+24:27:03.7 |
HIP 89706 |
4.30 |
| 2026-08-02 12:00 |
18:18:43.65 |
+24:26:22.7 |
HIP 89706 |
3.32 |
| 2026-08-03 00:00 |
18:18:39.65 |
+24:25:41.2 |
HIP 89706 |
2.50 |
| 2026-08-03 12:00 |
18:18:35.67 |
+24:24:59.4 |
HIP 89706 |
2.03 |
| 2026-08-04 00:00 |
18:18:31.72 |
+24:24:17.2 |
HIP 89706 |
2.15 |
| 2026-08-04 12:00 |
18:18:27.81 |
+24:23:34.6 |
HIP 89706 |
2.78 |
| 2026-08-05 00:00 |
18:18:23.93 |
+24:22:51.7 |
HIP 89706 |
3.67 |
| 2026-08-05 12:00 |
18:18:20.08 |
+24:22:08.4 |
HIP 89706 |
4.68 |
| 2026-08-06 00:00 |
18:18:16.26 |
+24:21:24.8 |
HIP 89706 |
5.73 |
| 2026-08-06 12:00 |
18:18:12.48 |
+24:20:40.8 |
HIP 89706 |
6.81 |
| 2026-08-07 00:00 |
18:18:08.73 |
+24:19:56.4 |
HIP 89706 |
7.90 |
| 2026-08-07 12:00 |
18:18:05.01 |
+24:19:11.7 |
HIP 89706 |
9.00 |
| 2026-08-08 00:00 |
18:18:01.33 |
+24:18:26.7 |
HIP 89706 |
10.11 |
| 2026-08-08 12:00 |
18:17:57.68 |
+24:17:41.3 |
HIP 89706 |
11.22 |
| 2026-08-09 00:00 |
18:17:54.07 |
+24:16:55.5 |
HIP 89706 |
12.34 |
| 2026-08-09 12:00 |
18:17:50.49 |
+24:16:09.5 |
HIP 89706 |
13.45 |
| 2026-08-10 00:00 |
18:17:46.94 |
+24:15:23.1 |
HIP 89706 |
14.56 |
| 2026-08-10 12:00 |
18:17:43.43 |
+24:14:36.3 |
HIP 89706 |
15.68 |
| 2026-08-11 00:00 |
18:17:39.96 |
+24:13:49.3 |
HIP 89706 |
16.79 |
| 2026-08-11 12:00 |
18:17:36.53 |
+24:13:01.9 |
HIP 89706 |
17.90 |
| 2026-08-12 00:00 |
18:17:33.13 |
+24:12:14.2 |
HIP 89706 |
19.01 |
| 2026-08-12 12:00 |
18:17:29.76 |
+24:11:26.1 |
HIP 89706 |
20.12 |
| 2026-08-13 00:00 |
18:17:26.44 |
+24:10:37.8 |
HIP 89706 |
21.23 |
| 2026-08-13 12:00 |
18:17:23.15 |
+24:09:49.1 |
HIP 89706 |
22.33 |
| 2026-08-14 00:00 |
18:17:19.90 |
+24:09:00.2 |
HIP 89493 |
23.19 |
| 2026-08-14 12:00 |
18:17:16.68 |
+24:08:10.9 |
HIP 89493 |
22.19 |
| 2026-08-15 00:00 |
18:17:13.51 |
+24:07:21.4 |
HIP 89493 |
21.20 |
| 2026-08-15 12:00 |
18:17:10.37 |
+24:06:31.5 |
HIP 89493 |
20.24 |
| 2026-08-16 00:00 |
18:17:07.27 |
+24:05:41.4 |
HIP 89493 |
19.30 |
| 2026-08-16 12:00 |
18:17:04.21 |
+24:04:51.0 |
HIP 89493 |
18.38 |
| 2026-08-17 00:00 |
18:17:01.20 |
+24:04:00.3 |
HIP 89493 |
17.48 |
| 2026-08-17 12:00 |
18:16:58.22 |
+24:03:09.3 |
HIP 89493 |
16.62 |
| 2026-08-18 00:00 |
18:16:55.28 |
+24:02:18.1 |
HIP 89493 |
15.80 |
| 2026-08-18 12:00 |
18:16:52.37 |
+24:01:26.6 |
HIP 89493 |
15.01 |
| 2026-08-19 00:00 |
18:16:49.51 |
+24:00:34.8 |
HIP 89493 |
14.28 |