| Parameter |
Value |
| Designation |
C/2015 D1 (SOHO) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2015-02-19T17:57:35.902080Z |
| Orbit solution date (soln_date, UTC) |
2021-04-16T12:05:35Z |
| Obs used |
417 |
| NEO |
Yes |
| M1 |
10.000 |
| K1 |
4.500 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2015-02-20.0000000 |
| e |
0.99432307 |
| q (au) |
0.028322 |
| a (au) |
4.989017 |
| i (deg) |
69.615618 |
| Ω (om, deg) |
95.881026 |
| ω (w, deg) |
234.955413 |
| M (ma, deg) |
0.022259 |
Magnitude
Scatter + Global Linear
$$
M_a = (10.386 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
10.386 |
| n |
2.000 |
| gf |
1.000 |
| gb |
-0.500 |
| 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 |
| 2015-02-18 |
2015-02-19 |
+1.3163 |
+2.493 |
| 2015-02-19 |
2015-02-20 |
+4.2155 |
+6.540 |
| 2015-02-20 |
2015-03-17 |
-1.1628 |
-1.516 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-09-20 00:00 |
09:24:49.00 |
+63:03:37.6 |
HIP 46059 |
11.05 |
| 2026-09-20 12:00 |
09:24:54.06 |
+63:03:52.4 |
HIP 46059 |
11.36 |
| 2026-09-21 00:00 |
09:24:59.09 |
+63:04:07.5 |
HIP 46059 |
11.69 |
| 2026-09-21 12:00 |
09:25:04.08 |
+63:04:22.9 |
HIP 46059 |
12.04 |
| 2026-09-22 00:00 |
09:25:09.04 |
+63:04:38.5 |
HIP 46059 |
12.40 |
| 2026-09-22 12:00 |
09:25:13.97 |
+63:04:54.4 |
HIP 46059 |
12.78 |
| 2026-09-23 00:00 |
09:25:18.86 |
+63:05:10.6 |
HIP 46059 |
13.16 |
| 2026-09-23 12:00 |
09:25:23.72 |
+63:05:27.0 |
HIP 46059 |
13.57 |
| 2026-09-24 00:00 |
09:25:28.54 |
+63:05:43.7 |
HIP 46059 |
13.98 |
| 2026-09-24 12:00 |
09:25:33.33 |
+63:06:00.7 |
HIP 46059 |
14.40 |
| 2026-09-25 00:00 |
09:25:38.08 |
+63:06:17.9 |
HIP 46059 |
14.82 |
| 2026-09-25 12:00 |
09:25:42.79 |
+63:06:35.4 |
HIP 46059 |
15.26 |
| 2026-09-26 00:00 |
09:25:47.47 |
+63:06:53.2 |
HIP 46059 |
15.70 |
| 2026-09-26 12:00 |
09:25:52.12 |
+63:07:11.2 |
HIP 46059 |
16.14 |
| 2026-09-27 00:00 |
09:25:56.72 |
+63:07:29.5 |
HIP 46059 |
16.60 |
| 2026-09-27 12:00 |
09:26:01.29 |
+63:07:48.1 |
HIP 46059 |
17.05 |
| 2026-09-28 00:00 |
09:26:05.83 |
+63:08:06.9 |
HIP 46059 |
17.51 |
| 2026-09-28 12:00 |
09:26:10.32 |
+63:08:26.0 |
HIP 46059 |
17.97 |
| 2026-09-29 00:00 |
09:26:14.78 |
+63:08:45.3 |
HIP 46059 |
18.44 |
| 2026-09-29 12:00 |
09:26:19.19 |
+63:09:04.9 |
HIP 46059 |
18.91 |
| 2026-09-30 00:00 |
09:26:23.57 |
+63:09:24.8 |
HIP 46059 |
19.38 |
| 2026-09-30 12:00 |
09:26:27.91 |
+63:09:44.9 |
HIP 46059 |
19.85 |
| 2026-10-01 00:00 |
09:26:32.21 |
+63:10:05.3 |
HIP 46059 |
20.33 |
| 2026-10-01 12:00 |
09:26:36.48 |
+63:10:25.9 |
HIP 46059 |
20.80 |
| 2026-10-02 00:00 |
09:26:40.70 |
+63:10:46.8 |
HIP 46059 |
21.28 |
| 2026-10-02 12:00 |
09:26:44.88 |
+63:11:07.9 |
HIP 46059 |
21.76 |
| 2026-10-03 00:00 |
09:26:49.02 |
+63:11:29.3 |
HIP 46059 |
22.23 |
| 2026-10-03 12:00 |
09:26:53.12 |
+63:11:50.9 |
HIP 46059 |
22.71 |
| 2026-10-04 00:00 |
09:26:57.17 |
+63:12:12.8 |
HIP 46059 |
23.19 |
| 2026-10-04 12:00 |
09:27:01.19 |
+63:12:35.0 |
HIP 46059 |
23.67 |
| 2026-10-05 00:00 |
09:27:05.16 |
+63:12:57.4 |
HIP 46059 |
24.15 |
| 2026-10-05 12:00 |
09:27:09.10 |
+63:13:20.0 |
HIP 46059 |
24.63 |
| 2026-10-06 00:00 |
09:27:12.99 |
+63:13:42.9 |
HIP 46059 |
25.11 |
| 2026-10-06 12:00 |
09:27:16.83 |
+63:14:06.1 |
HIP 46059 |
25.59 |
| 2026-10-07 00:00 |
09:27:20.63 |
+63:14:29.4 |
HIP 46059 |
26.07 |
| 2026-10-07 12:00 |
09:27:24.39 |
+63:14:53.1 |
HIP 46059 |
26.55 |
| 2026-10-08 00:00 |
09:27:28.11 |
+63:15:16.9 |
HIP 46059 |
27.03 |
| 2026-10-08 12:00 |
09:27:31.78 |
+63:15:41.0 |
HIP 46059 |
27.50 |
| 2026-10-09 00:00 |
09:27:35.40 |
+63:16:05.4 |
HIP 46059 |
27.98 |
| 2026-10-09 12:00 |
09:27:38.98 |
+63:16:30.0 |
HIP 46059 |
28.46 |
| 2026-10-10 00:00 |
09:27:42.51 |
+63:16:54.8 |
HIP 46059 |
28.93 |
| 2026-10-10 12:00 |
09:27:46.00 |
+63:17:19.9 |
HIP 46733 |
28.86 |
| 2026-10-11 00:00 |
09:27:49.44 |
+63:17:45.2 |
HIP 46684 |
28.35 |