| Parameter |
Value |
| Designation |
C/1998 J1 (SOHO) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
1998-05-08T14:51:07.577280Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:29:53Z |
| Obs used |
318 |
| NEO |
- |
| M1 |
6.500 |
| K1 |
7.500 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
1998-06-09.0000000 |
| e |
1.00017217 |
| q (au) |
0.153214 |
| a (au) |
-889.893232 |
| i (deg) |
62.931830 |
| Ω (om, deg) |
351.648559 |
| ω (w, deg) |
110.557189 |
| M (ma, deg) |
0.001165 |
Magnitude
Scatter + Global Linear
$$
M_a = (6.621 + 2.438\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
6.621 |
| n |
2.438 |
| gf |
0.800 |
| gb |
-0.500 |
| k |
0.800 |
| δ90 |
1.000 |
| 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 |
| 1998-05-08 |
1998-05-20 |
+3.7861 |
+1.870 |
| 1998-05-20 |
1998-05-31 |
-2.0767 |
+0.554 |
| 1998-05-31 |
1998-07-02 |
+0.2386 |
-0.078 |
| 1998-07-02 |
1998-08-15 |
+14.9567 |
-2.015 |
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 |
22:23:16.11 |
-77:26:59.5 |
HIP 110078 |
18.02 |
| 2026-03-26 12:00 |
22:23:24.56 |
-77:27:11.2 |
HIP 110078 |
18.43 |
| 2026-03-27 00:00 |
22:23:32.98 |
-77:27:23.0 |
HIP 110078 |
18.84 |
| 2026-03-27 12:00 |
22:23:41.35 |
-77:27:35.1 |
HIP 110078 |
19.25 |
| 2026-03-28 00:00 |
22:23:49.69 |
-77:27:47.5 |
HIP 110852 |
19.34 |
| 2026-03-28 12:00 |
22:23:57.99 |
-77:28:00.0 |
HIP 110852 |
18.90 |
| 2026-03-29 00:00 |
22:24:06.24 |
-77:28:12.9 |
HIP 110852 |
18.47 |
| 2026-03-29 12:00 |
22:24:14.45 |
-77:28:25.9 |
HIP 110852 |
18.03 |
| 2026-03-30 00:00 |
22:24:22.62 |
-77:28:39.2 |
HIP 110852 |
17.60 |
| 2026-03-30 12:00 |
22:24:30.75 |
-77:28:52.7 |
HIP 110852 |
17.16 |
| 2026-03-31 00:00 |
22:24:38.84 |
-77:29:06.4 |
HIP 110852 |
16.73 |
| 2026-03-31 12:00 |
22:24:46.88 |
-77:29:20.4 |
HIP 110852 |
16.30 |
| 2026-04-01 00:00 |
22:24:54.88 |
-77:29:34.6 |
HIP 110852 |
15.87 |
| 2026-04-01 12:00 |
22:25:02.83 |
-77:29:49.0 |
HIP 110852 |
15.44 |
| 2026-04-02 00:00 |
22:25:10.74 |
-77:30:03.6 |
HIP 110852 |
15.01 |
| 2026-04-02 12:00 |
22:25:18.60 |
-77:30:18.5 |
HIP 110852 |
14.59 |
| 2026-04-03 00:00 |
22:25:26.42 |
-77:30:33.6 |
HIP 110852 |
14.17 |
| 2026-04-03 12:00 |
22:25:34.19 |
-77:30:48.9 |
HIP 110852 |
13.75 |
| 2026-04-04 00:00 |
22:25:41.92 |
-77:31:04.5 |
HIP 110852 |
13.33 |
| 2026-04-04 12:00 |
22:25:49.60 |
-77:31:20.3 |
HIP 110852 |
12.92 |
| 2026-04-05 00:00 |
22:25:57.23 |
-77:31:36.3 |
HIP 110852 |
12.50 |
| 2026-04-05 12:00 |
22:26:04.81 |
-77:31:52.5 |
HIP 110852 |
12.10 |
| 2026-04-06 00:00 |
22:26:12.34 |
-77:32:08.9 |
HIP 110852 |
11.69 |
| 2026-04-06 12:00 |
22:26:19.83 |
-77:32:25.6 |
HIP 110852 |
11.29 |
| 2026-04-07 00:00 |
22:26:27.26 |
-77:32:42.5 |
HIP 110852 |
10.90 |
| 2026-04-07 12:00 |
22:26:34.65 |
-77:32:59.5 |
HIP 110852 |
10.51 |
| 2026-04-08 00:00 |
22:26:41.99 |
-77:33:16.9 |
HIP 110852 |
10.12 |
| 2026-04-08 12:00 |
22:26:49.27 |
-77:33:34.4 |
HIP 110852 |
9.74 |
| 2026-04-09 00:00 |
22:26:56.50 |
-77:33:52.1 |
HIP 110852 |
9.37 |
| 2026-04-09 12:00 |
22:27:03.68 |
-77:34:10.1 |
HIP 110852 |
9.01 |
| 2026-04-10 00:00 |
22:27:10.81 |
-77:34:28.3 |
HIP 110852 |
8.66 |
| 2026-04-10 12:00 |
22:27:17.89 |
-77:34:46.6 |
HIP 110852 |
8.31 |
| 2026-04-11 00:00 |
22:27:24.91 |
-77:35:05.2 |
HIP 110852 |
7.98 |
| 2026-04-11 12:00 |
22:27:31.88 |
-77:35:24.0 |
HIP 110852 |
7.66 |
| 2026-04-12 00:00 |
22:27:38.80 |
-77:35:43.0 |
HIP 110852 |
7.36 |
| 2026-04-12 12:00 |
22:27:45.65 |
-77:36:02.3 |
HIP 110852 |
7.07 |
| 2026-04-13 00:00 |
22:27:52.46 |
-77:36:21.7 |
HIP 110852 |
6.80 |
| 2026-04-13 12:00 |
22:27:59.21 |
-77:36:41.3 |
HIP 110852 |
6.55 |
| 2026-04-14 00:00 |
22:28:05.90 |
-77:37:01.2 |
HIP 110852 |
6.33 |
| 2026-04-14 12:00 |
22:28:12.53 |
-77:37:21.2 |
HIP 110852 |
6.13 |
| 2026-04-15 00:00 |
22:28:19.11 |
-77:37:41.4 |
HIP 110852 |
5.96 |
| 2026-04-15 12:00 |
22:28:25.63 |
-77:38:01.9 |
HIP 110852 |
5.82 |
| 2026-04-16 00:00 |
22:28:32.09 |
-77:38:22.5 |
HIP 110852 |
5.72 |