| 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) |
| 2026-03-26 00:00 |
02:56:15.76 |
+44:23:00.8 |
HIP 13703 |
17.64 |
| 2026-03-26 12:00 |
02:56:19.82 |
+44:22:53.0 |
HIP 13703 |
17.44 |
| 2026-03-27 00:00 |
02:56:23.90 |
+44:22:45.6 |
HIP 13802 |
16.92 |
| 2026-03-27 12:00 |
02:56:28.02 |
+44:22:38.4 |
HIP 13802 |
16.36 |
| 2026-03-28 00:00 |
02:56:32.16 |
+44:22:31.5 |
HIP 13802 |
15.81 |
| 2026-03-28 12:00 |
02:56:36.34 |
+44:22:24.9 |
HIP 13802 |
15.27 |
| 2026-03-29 00:00 |
02:56:40.54 |
+44:22:18.6 |
HIP 13802 |
14.75 |
| 2026-03-29 12:00 |
02:56:44.77 |
+44:22:12.6 |
HIP 13802 |
14.24 |
| 2026-03-30 00:00 |
02:56:49.03 |
+44:22:06.9 |
HIP 13802 |
13.74 |
| 2026-03-30 12:00 |
02:56:53.31 |
+44:22:01.4 |
HIP 13802 |
13.26 |
| 2026-03-31 00:00 |
02:56:57.63 |
+44:21:56.2 |
HIP 13802 |
12.81 |
| 2026-03-31 12:00 |
02:57:01.97 |
+44:21:51.3 |
HIP 13802 |
12.38 |
| 2026-04-01 00:00 |
02:57:06.33 |
+44:21:46.7 |
HIP 13802 |
11.98 |
| 2026-04-01 12:00 |
02:57:10.73 |
+44:21:42.3 |
HIP 13804 |
11.60 |
| 2026-04-02 00:00 |
02:57:15.15 |
+44:21:38.3 |
HIP 13804 |
11.25 |
| 2026-04-02 12:00 |
02:57:19.59 |
+44:21:34.5 |
HIP 13804 |
10.94 |
| 2026-04-03 00:00 |
02:57:24.06 |
+44:21:31.0 |
HIP 13804 |
10.67 |
| 2026-04-03 12:00 |
02:57:28.55 |
+44:21:27.8 |
HIP 13804 |
10.46 |
| 2026-04-04 00:00 |
02:57:33.07 |
+44:21:24.9 |
HIP 13804 |
10.29 |
| 2026-04-04 12:00 |
02:57:37.62 |
+44:21:22.2 |
HIP 13804 |
10.19 |
| 2026-04-05 00:00 |
02:57:42.18 |
+44:21:19.8 |
HIP 13804 |
10.14 |
| 2026-04-05 12:00 |
02:57:46.77 |
+44:21:17.7 |
HIP 13804 |
10.15 |
| 2026-04-06 00:00 |
02:57:51.39 |
+44:21:15.9 |
HIP 13804 |
10.23 |
| 2026-04-06 12:00 |
02:57:56.03 |
+44:21:14.4 |
HIP 13804 |
10.36 |
| 2026-04-07 00:00 |
02:58:00.69 |
+44:21:13.1 |
HIP 13804 |
10.56 |
| 2026-04-07 12:00 |
02:58:05.37 |
+44:21:12.1 |
HIP 13804 |
10.81 |
| 2026-04-08 00:00 |
02:58:10.07 |
+44:21:11.4 |
HIP 13804 |
11.12 |
| 2026-04-08 12:00 |
02:58:14.80 |
+44:21:11.0 |
HIP 13804 |
11.48 |
| 2026-04-09 00:00 |
02:58:19.55 |
+44:21:10.8 |
HIP 13804 |
11.89 |
| 2026-04-09 12:00 |
02:58:24.32 |
+44:21:11.0 |
HIP 13804 |
12.33 |
| 2026-04-10 00:00 |
02:58:29.11 |
+44:21:11.4 |
HIP 13804 |
12.82 |
| 2026-04-10 12:00 |
02:58:33.92 |
+44:21:12.1 |
HIP 13804 |
13.35 |
| 2026-04-11 00:00 |
02:58:38.75 |
+44:21:13.0 |
HIP 13804 |
13.90 |
| 2026-04-11 12:00 |
02:58:43.60 |
+44:21:14.2 |
HIP 13804 |
14.49 |
| 2026-04-12 00:00 |
02:58:48.47 |
+44:21:15.7 |
HIP 13804 |
15.10 |
| 2026-04-12 12:00 |
02:58:53.36 |
+44:21:17.5 |
HIP 13804 |
15.74 |
| 2026-04-13 00:00 |
02:58:58.26 |
+44:21:19.6 |
HIP 13804 |
16.40 |
| 2026-04-13 12:00 |
02:59:03.19 |
+44:21:21.9 |
HIP 13804 |
17.07 |
| 2026-04-14 00:00 |
02:59:08.13 |
+44:21:24.5 |
HIP 13804 |
17.77 |
| 2026-04-14 12:00 |
02:59:13.09 |
+44:21:27.4 |
HIP 13804 |
18.48 |
| 2026-04-15 00:00 |
02:59:18.07 |
+44:21:30.5 |
HIP 13804 |
19.21 |
| 2026-04-15 12:00 |
02:59:23.07 |
+44:21:33.9 |
HIP 13804 |
19.95 |
| 2026-04-16 00:00 |
02:59:28.08 |
+44:21:37.6 |
HIP 13804 |
20.70 |