| 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) |
| 2026-07-29 00:00 |
22:22:36.67 |
-79:13:31.9 |
HIP 110282 |
7.65 |
| 2026-07-29 12:00 |
22:22:26.74 |
-79:13:49.9 |
HIP 110282 |
7.10 |
| 2026-07-30 00:00 |
22:22:16.75 |
-79:14:07.7 |
HIP 110282 |
6.55 |
| 2026-07-30 12:00 |
22:22:06.72 |
-79:14:25.2 |
HIP 110282 |
6.00 |
| 2026-07-31 00:00 |
22:21:56.63 |
-79:14:42.5 |
HIP 110282 |
5.45 |
| 2026-07-31 12:00 |
22:21:46.50 |
-79:14:59.5 |
HIP 110282 |
4.89 |
| 2026-08-01 00:00 |
22:21:36.31 |
-79:15:16.3 |
HIP 110282 |
4.34 |
| 2026-08-01 12:00 |
22:21:26.08 |
-79:15:32.9 |
HIP 110282 |
3.79 |
| 2026-08-02 00:00 |
22:21:15.80 |
-79:15:49.2 |
HIP 110282 |
3.25 |
| 2026-08-02 12:00 |
22:21:05.47 |
-79:16:05.2 |
HIP 110282 |
2.70 |
| 2026-08-03 00:00 |
22:20:55.10 |
-79:16:21.0 |
HIP 110282 |
2.16 |
| 2026-08-03 12:00 |
22:20:44.69 |
-79:16:36.6 |
HIP 110282 |
1.62 |
| 2026-08-04 00:00 |
22:20:34.23 |
-79:16:51.8 |
HIP 110282 |
1.09 |
| 2026-08-04 12:00 |
22:20:23.73 |
-79:17:06.9 |
HIP 110282 |
0.62 |
| 2026-08-05 00:00 |
22:20:13.18 |
-79:17:21.6 |
HIP 110282 |
0.42 |
| 2026-08-05 12:00 |
22:20:02.60 |
-79:17:36.2 |
HIP 110282 |
0.75 |
| 2026-08-06 00:00 |
22:19:51.97 |
-79:17:50.4 |
HIP 110282 |
1.25 |
| 2026-08-06 12:00 |
22:19:41.30 |
-79:18:04.4 |
HIP 110282 |
1.78 |
| 2026-08-07 00:00 |
22:19:30.60 |
-79:18:18.1 |
HIP 110282 |
2.32 |
| 2026-08-07 12:00 |
22:19:19.86 |
-79:18:31.6 |
HIP 110282 |
2.86 |
| 2026-08-08 00:00 |
22:19:09.08 |
-79:18:44.8 |
HIP 110282 |
3.40 |
| 2026-08-08 12:00 |
22:18:58.27 |
-79:18:57.7 |
HIP 110282 |
3.94 |
| 2026-08-09 00:00 |
22:18:47.42 |
-79:19:10.4 |
HIP 110282 |
4.49 |
| 2026-08-09 12:00 |
22:18:36.54 |
-79:19:22.8 |
HIP 110282 |
5.03 |
| 2026-08-10 00:00 |
22:18:25.62 |
-79:19:34.9 |
HIP 110282 |
5.58 |
| 2026-08-10 12:00 |
22:18:14.68 |
-79:19:46.7 |
HIP 110282 |
6.12 |
| 2026-08-11 00:00 |
22:18:03.70 |
-79:19:58.3 |
HIP 110282 |
6.66 |
| 2026-08-11 12:00 |
22:17:52.70 |
-79:20:09.6 |
HIP 110282 |
7.21 |
| 2026-08-12 00:00 |
22:17:41.66 |
-79:20:20.6 |
HIP 109878 |
6.76 |
| 2026-08-12 12:00 |
22:17:30.60 |
-79:20:31.3 |
HIP 109878 |
6.23 |
| 2026-08-13 00:00 |
22:17:19.51 |
-79:20:41.8 |
HIP 109878 |
5.70 |
| 2026-08-13 12:00 |
22:17:08.40 |
-79:20:52.0 |
HIP 109878 |
5.17 |
| 2026-08-14 00:00 |
22:16:57.26 |
-79:21:01.9 |
HIP 109878 |
4.65 |
| 2026-08-14 12:00 |
22:16:46.10 |
-79:21:11.5 |
HIP 109878 |
4.13 |
| 2026-08-15 00:00 |
22:16:34.92 |
-79:21:20.8 |
HIP 109878 |
3.62 |
| 2026-08-15 12:00 |
22:16:23.72 |
-79:21:29.9 |
HIP 109878 |
3.12 |
| 2026-08-16 00:00 |
22:16:12.50 |
-79:21:38.6 |
HIP 109878 |
2.62 |
| 2026-08-16 12:00 |
22:16:01.26 |
-79:21:47.1 |
HIP 109878 |
2.15 |
| 2026-08-17 00:00 |
22:15:50.00 |
-79:21:55.3 |
HIP 109878 |
1.71 |
| 2026-08-17 12:00 |
22:15:38.72 |
-79:22:03.2 |
HIP 109878 |
1.35 |
| 2026-08-18 00:00 |
22:15:27.44 |
-79:22:10.8 |
HIP 109878 |
1.12 |
| 2026-08-18 12:00 |
22:15:16.13 |
-79:22:18.1 |
HIP 109878 |
1.13 |
| 2026-08-19 00:00 |
22:15:04.81 |
-79:22:25.2 |
HIP 109878 |
1.36 |