| Parameter |
Value |
| Designation |
C/2015 G2 (MASTER) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2015-05-23T18:53:55.887360Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:33:09Z |
| Obs used |
562 |
| NEO |
- |
| M1 |
12.000 |
| K1 |
6.000 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2015-08-16.0000000 |
| e |
1.00039511 |
| q (au) |
0.779858 |
| a (au) |
-1973.798171 |
| i (deg) |
147.562721 |
| Ω (om, deg) |
110.058840 |
| ω (w, deg) |
257.458784 |
| M (ma, deg) |
0.000947 |
Magnitude
Scatter + Global Linear
$$
M_a = (11.448 + 3.318\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
11.448 |
| n |
3.318 |
| gf |
1.000 |
| gb |
-0.627 |
| k |
0.956 |
| 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 |
| 2015-03-30 |
2015-04-10 |
-18.6339 |
+0.055 |
| 2015-04-10 |
2015-04-24 |
-23.7310 |
-0.653 |
| 2015-04-24 |
2015-05-23 |
+8.8729 |
-1.009 |
| 2015-05-23 |
2016-02-07 |
+2.0675 |
-1.196 |
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 |
03:14:03.91 |
+45:43:02.7 |
HIP 14916 |
27.86 |
| 2026-07-29 12:00 |
03:14:05.06 |
+45:43:34.8 |
HIP 14916 |
28.41 |
| 2026-07-30 00:00 |
03:14:06.16 |
+45:44:06.9 |
HIP 14923 |
28.29 |
| 2026-07-30 12:00 |
03:14:07.21 |
+45:44:39.0 |
HIP 14923 |
27.96 |
| 2026-07-31 00:00 |
03:14:08.22 |
+45:45:11.0 |
HIP 14923 |
27.65 |
| 2026-07-31 12:00 |
03:14:09.18 |
+45:45:43.0 |
HIP 14923 |
27.33 |
| 2026-08-01 00:00 |
03:14:10.09 |
+45:46:14.9 |
HIP 14923 |
27.02 |
| 2026-08-01 12:00 |
03:14:10.96 |
+45:46:46.7 |
HIP 14923 |
26.71 |
| 2026-08-02 00:00 |
03:14:11.78 |
+45:47:18.5 |
HIP 14923 |
26.41 |
| 2026-08-02 12:00 |
03:14:12.55 |
+45:47:50.2 |
HIP 14923 |
26.10 |
| 2026-08-03 00:00 |
03:14:13.27 |
+45:48:21.9 |
HIP 14923 |
25.81 |
| 2026-08-03 12:00 |
03:14:13.94 |
+45:48:53.5 |
HIP 14923 |
25.51 |
| 2026-08-04 00:00 |
03:14:14.57 |
+45:49:25.0 |
HIP 14923 |
25.22 |
| 2026-08-04 12:00 |
03:14:15.15 |
+45:49:56.5 |
HIP 14923 |
24.92 |
| 2026-08-05 00:00 |
03:14:15.68 |
+45:50:27.9 |
HIP 14923 |
24.64 |
| 2026-08-05 12:00 |
03:14:16.16 |
+45:50:59.2 |
HIP 14923 |
24.35 |
| 2026-08-06 00:00 |
03:14:16.60 |
+45:51:30.4 |
HIP 14923 |
24.07 |
| 2026-08-06 12:00 |
03:14:16.98 |
+45:52:01.6 |
HIP 14923 |
23.79 |
| 2026-08-07 00:00 |
03:14:17.32 |
+45:52:32.7 |
HIP 14923 |
23.51 |
| 2026-08-07 12:00 |
03:14:17.61 |
+45:53:03.7 |
HIP 14923 |
23.23 |
| 2026-08-08 00:00 |
03:14:17.84 |
+45:53:34.6 |
HIP 14923 |
22.96 |
| 2026-08-08 12:00 |
03:14:18.03 |
+45:54:05.5 |
HIP 14923 |
22.69 |
| 2026-08-09 00:00 |
03:14:18.17 |
+45:54:36.2 |
HIP 14923 |
22.42 |
| 2026-08-09 12:00 |
03:14:18.26 |
+45:55:06.9 |
HIP 14923 |
22.15 |
| 2026-08-10 00:00 |
03:14:18.30 |
+45:55:37.4 |
HIP 14923 |
21.89 |
| 2026-08-10 12:00 |
03:14:18.29 |
+45:56:07.9 |
HIP 14923 |
21.63 |
| 2026-08-11 00:00 |
03:14:18.23 |
+45:56:38.3 |
HIP 14923 |
21.37 |
| 2026-08-11 12:00 |
03:14:18.12 |
+45:57:08.6 |
HIP 14923 |
21.11 |
| 2026-08-12 00:00 |
03:14:17.96 |
+45:57:38.7 |
HIP 14923 |
20.85 |
| 2026-08-12 12:00 |
03:14:17.75 |
+45:58:08.8 |
HIP 14923 |
20.60 |
| 2026-08-13 00:00 |
03:14:17.49 |
+45:58:38.8 |
HIP 14923 |
20.35 |
| 2026-08-13 12:00 |
03:14:17.18 |
+45:59:08.6 |
HIP 14923 |
20.10 |
| 2026-08-14 00:00 |
03:14:16.82 |
+45:59:38.3 |
HIP 14923 |
19.85 |
| 2026-08-14 12:00 |
03:14:16.41 |
+46:00:08.0 |
HIP 14923 |
19.60 |
| 2026-08-15 00:00 |
03:14:15.95 |
+46:00:37.5 |
HIP 14923 |
19.36 |
| 2026-08-15 12:00 |
03:14:15.44 |
+46:01:06.8 |
HIP 14923 |
19.12 |
| 2026-08-16 00:00 |
03:14:14.87 |
+46:01:36.1 |
HIP 14923 |
18.88 |
| 2026-08-16 12:00 |
03:14:14.26 |
+46:02:05.2 |
HIP 14923 |
18.64 |
| 2026-08-17 00:00 |
03:14:13.60 |
+46:02:34.3 |
HIP 14923 |
18.41 |
| 2026-08-17 12:00 |
03:14:12.88 |
+46:03:03.1 |
HIP 14923 |
18.17 |
| 2026-08-18 00:00 |
03:14:12.11 |
+46:03:31.9 |
HIP 14923 |
17.94 |
| 2026-08-18 12:00 |
03:14:11.30 |
+46:04:00.5 |
HIP 14923 |
17.72 |
| 2026-08-19 00:00 |
03:14:10.43 |
+46:04:29.0 |
HIP 14923 |
17.49 |