| Parameter |
Value |
| Designation |
C/1998 U5 (LINEAR) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
1998-12-21T18:14:25.114560Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:29:57Z |
| Obs used |
406 |
| NEO |
- |
| M1 |
11.000 |
| K1 |
15.500 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
1998-12-01.0000000 |
| e |
0.98797943 |
| q (au) |
1.236453 |
| a (au) |
102.861449 |
| i (deg) |
131.764750 |
| Ω (om, deg) |
66.650605 |
| ω (w, deg) |
51.134275 |
| M (ma, deg) |
359.980387 |
Magnitude
Scatter + Global Linear
$$
M_a = (8.137 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
8.137 |
| n |
6.000 |
| gf |
0.997 |
| gb |
-0.503 |
| 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 |
| 1998-10-30 |
1998-12-21 |
+23.4645 |
-2.542 |
| 1998-12-21 |
1999-05-11 |
-3.5652 |
+0.381 |
| 1999-05-11 |
1999-12-09 |
-44.9953 |
+16.194 |
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 |
13:55:20.51 |
-38:28:50.3 |
HIP 68073 |
15.33 |
| 2026-09-20 12:00 |
13:55:22.87 |
-38:28:51.4 |
HIP 68073 |
15.00 |
| 2026-09-21 00:00 |
13:55:25.23 |
-38:28:52.6 |
HIP 68073 |
14.67 |
| 2026-09-21 12:00 |
13:55:27.61 |
-38:28:54.0 |
HIP 68073 |
14.34 |
| 2026-09-22 00:00 |
13:55:30.00 |
-38:28:55.5 |
HIP 68073 |
14.02 |
| 2026-09-22 12:00 |
13:55:32.41 |
-38:28:57.2 |
HIP 68073 |
13.71 |
| 2026-09-23 00:00 |
13:55:34.83 |
-38:28:59.1 |
HIP 68073 |
13.40 |
| 2026-09-23 12:00 |
13:55:37.26 |
-38:29:01.2 |
HIP 68073 |
13.09 |
| 2026-09-24 00:00 |
13:55:39.70 |
-38:29:03.4 |
HIP 68073 |
12.80 |
| 2026-09-24 12:00 |
13:55:42.15 |
-38:29:05.8 |
HIP 68073 |
12.51 |
| 2026-09-25 00:00 |
13:55:44.62 |
-38:29:08.3 |
HIP 68073 |
12.23 |
| 2026-09-25 12:00 |
13:55:47.09 |
-38:29:11.0 |
HIP 68073 |
11.96 |
| 2026-09-26 00:00 |
13:55:49.58 |
-38:29:13.9 |
HIP 68073 |
11.70 |
| 2026-09-26 12:00 |
13:55:52.08 |
-38:29:16.9 |
HIP 68073 |
11.45 |
| 2026-09-27 00:00 |
13:55:54.59 |
-38:29:20.1 |
HIP 68073 |
11.21 |
| 2026-09-27 12:00 |
13:55:57.11 |
-38:29:23.5 |
HIP 68073 |
10.99 |
| 2026-09-28 00:00 |
13:55:59.65 |
-38:29:27.1 |
HIP 68073 |
10.78 |
| 2026-09-28 12:00 |
13:56:02.19 |
-38:29:30.8 |
HIP 68073 |
10.59 |
| 2026-09-29 00:00 |
13:56:04.74 |
-38:29:34.6 |
HIP 68073 |
10.42 |
| 2026-09-29 12:00 |
13:56:07.31 |
-38:29:38.7 |
HIP 68128 |
10.22 |
| 2026-09-30 00:00 |
13:56:09.88 |
-38:29:42.8 |
HIP 68128 |
9.85 |
| 2026-09-30 12:00 |
13:56:12.46 |
-38:29:47.2 |
HIP 68128 |
9.49 |
| 2026-10-01 00:00 |
13:56:15.06 |
-38:29:51.7 |
HIP 68128 |
9.15 |
| 2026-10-01 12:00 |
13:56:17.66 |
-38:29:56.4 |
HIP 68128 |
8.83 |
| 2026-10-02 00:00 |
13:56:20.27 |
-38:30:01.3 |
HIP 68128 |
8.53 |
| 2026-10-02 12:00 |
13:56:22.90 |
-38:30:06.3 |
HIP 68128 |
8.24 |
| 2026-10-03 00:00 |
13:56:25.53 |
-38:30:11.4 |
HIP 68128 |
7.99 |
| 2026-10-03 12:00 |
13:56:28.17 |
-38:30:16.8 |
HIP 68128 |
7.76 |
| 2026-10-04 00:00 |
13:56:30.82 |
-38:30:22.3 |
HIP 68128 |
7.56 |
| 2026-10-04 12:00 |
13:56:33.47 |
-38:30:27.9 |
HIP 68128 |
7.40 |
| 2026-10-05 00:00 |
13:56:36.14 |
-38:30:33.7 |
HIP 68128 |
7.27 |
| 2026-10-05 12:00 |
13:56:38.82 |
-38:30:39.7 |
HIP 68128 |
7.18 |
| 2026-10-06 00:00 |
13:56:41.50 |
-38:30:45.9 |
HIP 68128 |
7.14 |
| 2026-10-06 12:00 |
13:56:44.19 |
-38:30:52.2 |
HIP 68166 |
6.88 |
| 2026-10-07 00:00 |
13:56:46.89 |
-38:30:58.6 |
HIP 68166 |
6.35 |
| 2026-10-07 12:00 |
13:56:49.59 |
-38:31:05.2 |
HIP 68166 |
5.82 |
| 2026-10-08 00:00 |
13:56:52.30 |
-38:31:12.0 |
HIP 68166 |
5.28 |
| 2026-10-08 12:00 |
13:56:55.02 |
-38:31:19.0 |
HIP 68166 |
4.75 |
| 2026-10-09 00:00 |
13:56:57.75 |
-38:31:26.1 |
HIP 68166 |
4.21 |
| 2026-10-09 12:00 |
13:57:00.48 |
-38:31:33.3 |
HIP 68166 |
3.68 |
| 2026-10-10 00:00 |
13:57:03.22 |
-38:31:40.7 |
HIP 68166 |
3.16 |
| 2026-10-10 12:00 |
13:57:05.97 |
-38:31:48.3 |
HIP 68166 |
2.64 |
| 2026-10-11 00:00 |
13:57:08.72 |
-38:31:56.0 |
HIP 68166 |
2.14 |