| 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) |
| 2026-07-29 00:00 |
09:14:00.93 |
+63:04:00.5 |
HIP 45323 |
6.61 |
| 2026-07-29 12:00 |
09:14:07.37 |
+63:03:46.0 |
HIP 45323 |
6.76 |
| 2026-07-30 00:00 |
09:14:13.83 |
+63:03:31.7 |
HIP 45323 |
6.98 |
| 2026-07-30 12:00 |
09:14:20.28 |
+63:03:17.7 |
HIP 45323 |
7.28 |
| 2026-07-31 00:00 |
09:14:26.75 |
+63:03:04.0 |
HIP 45323 |
7.63 |
| 2026-07-31 12:00 |
09:14:33.21 |
+63:02:50.5 |
HIP 45323 |
8.04 |
| 2026-08-01 00:00 |
09:14:39.69 |
+63:02:37.2 |
HIP 45323 |
8.50 |
| 2026-08-01 12:00 |
09:14:46.17 |
+63:02:24.2 |
HIP 45323 |
8.99 |
| 2026-08-02 00:00 |
09:14:52.65 |
+63:02:11.5 |
HIP 45323 |
9.52 |
| 2026-08-02 12:00 |
09:14:59.14 |
+63:01:59.0 |
HIP 45323 |
10.07 |
| 2026-08-03 00:00 |
09:15:05.64 |
+63:01:46.7 |
HIP 45323 |
10.65 |
| 2026-08-03 12:00 |
09:15:12.13 |
+63:01:34.8 |
HIP 45323 |
11.24 |
| 2026-08-04 00:00 |
09:15:18.63 |
+63:01:23.1 |
HIP 45323 |
11.85 |
| 2026-08-04 12:00 |
09:15:25.13 |
+63:01:11.6 |
HIP 45323 |
12.48 |
| 2026-08-05 00:00 |
09:15:31.64 |
+63:01:00.4 |
HIP 45323 |
13.12 |
| 2026-08-05 12:00 |
09:15:38.15 |
+63:00:49.5 |
HIP 45323 |
13.76 |
| 2026-08-06 00:00 |
09:15:44.66 |
+63:00:38.8 |
HIP 45323 |
14.42 |
| 2026-08-06 12:00 |
09:15:51.17 |
+63:00:28.4 |
HIP 45323 |
15.08 |
| 2026-08-07 00:00 |
09:15:57.68 |
+63:00:18.3 |
HIP 45323 |
15.74 |
| 2026-08-07 12:00 |
09:16:04.19 |
+63:00:08.4 |
HIP 45323 |
16.42 |
| 2026-08-08 00:00 |
09:16:10.70 |
+62:59:58.8 |
HIP 45323 |
17.09 |
| 2026-08-08 12:00 |
09:16:17.22 |
+62:59:49.5 |
HIP 45323 |
17.77 |
| 2026-08-09 00:00 |
09:16:23.73 |
+62:59:40.4 |
HIP 45323 |
18.46 |
| 2026-08-09 12:00 |
09:16:30.24 |
+62:59:31.6 |
HIP 45693 |
18.62 |
| 2026-08-10 00:00 |
09:16:36.75 |
+62:59:23.1 |
HIP 45693 |
17.91 |
| 2026-08-10 12:00 |
09:16:43.26 |
+62:59:14.8 |
HIP 45693 |
17.19 |
| 2026-08-11 00:00 |
09:16:49.77 |
+62:59:06.8 |
HIP 45693 |
16.49 |
| 2026-08-11 12:00 |
09:16:56.27 |
+62:58:59.1 |
HIP 45693 |
15.79 |
| 2026-08-12 00:00 |
09:17:02.77 |
+62:58:51.7 |
HIP 45693 |
15.10 |
| 2026-08-12 12:00 |
09:17:09.27 |
+62:58:44.5 |
HIP 45693 |
14.42 |
| 2026-08-13 00:00 |
09:17:15.76 |
+62:58:37.6 |
HIP 45693 |
13.75 |
| 2026-08-13 12:00 |
09:17:22.25 |
+62:58:31.0 |
HIP 45693 |
13.10 |
| 2026-08-14 00:00 |
09:17:28.74 |
+62:58:24.6 |
HIP 45693 |
12.45 |
| 2026-08-14 12:00 |
09:17:35.22 |
+62:58:18.6 |
HIP 45693 |
11.82 |
| 2026-08-15 00:00 |
09:17:41.69 |
+62:58:12.8 |
HIP 45693 |
11.21 |
| 2026-08-15 12:00 |
09:17:48.16 |
+62:58:07.3 |
HIP 45693 |
10.61 |
| 2026-08-16 00:00 |
09:17:54.62 |
+62:58:02.0 |
HIP 45693 |
10.05 |
| 2026-08-16 12:00 |
09:18:01.07 |
+62:57:57.1 |
HIP 45693 |
9.51 |
| 2026-08-17 00:00 |
09:18:07.52 |
+62:57:52.4 |
HIP 45693 |
9.00 |
| 2026-08-17 12:00 |
09:18:13.96 |
+62:57:48.0 |
HIP 45693 |
8.53 |
| 2026-08-18 00:00 |
09:18:20.39 |
+62:57:43.9 |
HIP 45693 |
8.10 |
| 2026-08-18 12:00 |
09:18:26.82 |
+62:57:40.1 |
HIP 45693 |
7.73 |
| 2026-08-19 00:00 |
09:18:33.23 |
+62:57:36.5 |
HIP 45693 |
7.41 |