C/2015 G2 (MASTER)
| 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
$$
M_a = (11.448 + 3.319\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
11.448 |
| n |
3.319 |
| 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 |
-18.6325 |
+0.055 |
| 2015-04-10 |
2015-04-24 |
-23.7298 |
-0.653 |
| 2015-04-24 |
2015-05-23 |
+8.8733 |
-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) |
| 2026-02-03 00:00 |
02:52:53.65 |
+44:59:29.7 |
HIP 13360 |
12.24 |
| 2026-02-03 12:00 |
02:52:53.18 |
+44:58:56.8 |
HIP 13360 |
11.91 |
| 2026-02-04 00:00 |
02:52:52.77 |
+44:58:24.0 |
HIP 13360 |
11.61 |
| 2026-02-04 12:00 |
02:52:52.42 |
+44:57:51.3 |
HIP 13360 |
11.35 |
| 2026-02-05 00:00 |
02:52:52.12 |
+44:57:18.9 |
HIP 13360 |
11.11 |
| 2026-02-05 12:00 |
02:52:51.87 |
+44:56:46.6 |
HIP 13360 |
10.90 |
| 2026-02-06 00:00 |
02:52:51.67 |
+44:56:14.5 |
HIP 13360 |
10.73 |
| 2026-02-06 12:00 |
02:52:51.53 |
+44:55:42.6 |
HIP 13360 |
10.59 |
| 2026-02-07 00:00 |
02:52:51.44 |
+44:55:10.8 |
HIP 13360 |
10.48 |
| 2026-02-07 12:00 |
02:52:51.41 |
+44:54:39.3 |
HIP 13360 |
10.41 |
| 2026-02-08 00:00 |
02:52:51.43 |
+44:54:07.9 |
HIP 13360 |
10.38 |
| 2026-02-08 12:00 |
02:52:51.50 |
+44:53:36.7 |
HIP 13360 |
10.38 |
| 2026-02-09 00:00 |
02:52:51.62 |
+44:53:05.7 |
HIP 13360 |
10.42 |
| 2026-02-09 12:00 |
02:52:51.80 |
+44:52:34.9 |
HIP 13360 |
10.49 |
| 2026-02-10 00:00 |
02:52:52.03 |
+44:52:04.3 |
HIP 13360 |
10.60 |
| 2026-02-10 12:00 |
02:52:52.32 |
+44:51:33.9 |
HIP 13360 |
10.74 |
| 2026-02-11 00:00 |
02:52:52.65 |
+44:51:03.7 |
HIP 13360 |
10.90 |
| 2026-02-11 12:00 |
02:52:53.04 |
+44:50:33.7 |
HIP 13360 |
11.10 |
| 2026-02-12 00:00 |
02:52:53.48 |
+44:50:03.9 |
HIP 13360 |
11.32 |
| 2026-02-12 12:00 |
02:52:53.97 |
+44:49:34.3 |
HIP 13360 |
11.57 |
| 2026-02-13 00:00 |
02:52:54.52 |
+44:49:04.9 |
HIP 13360 |
11.84 |
| 2026-02-13 12:00 |
02:52:55.11 |
+44:48:35.7 |
HIP 13360 |
12.14 |
| 2026-02-14 00:00 |
02:52:55.76 |
+44:48:06.8 |
HIP 13360 |
12.45 |
| 2026-02-14 12:00 |
02:52:56.46 |
+44:47:38.0 |
HIP 13360 |
12.78 |
| 2026-02-15 00:00 |
02:52:57.21 |
+44:47:09.5 |
HIP 13360 |
13.13 |
| 2026-02-15 12:00 |
02:52:58.02 |
+44:46:41.2 |
HIP 13360 |
13.49 |
| 2026-02-16 00:00 |
02:52:58.87 |
+44:46:13.1 |
HIP 13360 |
13.86 |
| 2026-02-16 12:00 |
02:52:59.78 |
+44:45:45.2 |
HIP 13360 |
14.25 |
| 2026-02-17 00:00 |
02:53:00.73 |
+44:45:17.6 |
HIP 13360 |
14.65 |
| 2026-02-17 12:00 |
02:53:01.74 |
+44:44:50.1 |
HIP 13360 |
15.06 |
| 2026-02-18 00:00 |
02:53:02.80 |
+44:44:22.9 |
HIP 13360 |
15.48 |
| 2026-02-18 12:00 |
02:53:03.91 |
+44:43:56.0 |
HIP 13360 |
15.91 |
| 2026-02-19 00:00 |
02:53:05.06 |
+44:43:29.2 |
HIP 13360 |
16.35 |
| 2026-02-19 12:00 |
02:53:06.27 |
+44:43:02.7 |
HIP 13360 |
16.79 |
| 2026-02-20 00:00 |
02:53:07.53 |
+44:42:36.5 |
HIP 13360 |
17.24 |
| 2026-02-20 12:00 |
02:53:08.84 |
+44:42:10.4 |
HIP 13360 |
17.70 |
| 2026-02-21 00:00 |
02:53:10.19 |
+44:41:44.7 |
HIP 13360 |
18.17 |
| 2026-02-21 12:00 |
02:53:11.60 |
+44:41:19.1 |
HIP 13360 |
18.63 |
| 2026-02-22 00:00 |
02:53:13.05 |
+44:40:53.8 |
HIP 13360 |
19.11 |
| 2026-02-22 12:00 |
02:53:14.55 |
+44:40:28.7 |
HIP 13360 |
19.59 |
| 2026-02-23 00:00 |
02:53:16.10 |
+44:40:03.9 |
HIP 13360 |
20.07 |
| 2026-02-23 12:00 |
02:53:17.70 |
+44:39:39.3 |
HIP 13360 |
20.56 |
| 2026-02-24 00:00 |
02:53:19.35 |
+44:39:15.0 |
HIP 13360 |
21.05 |