C/1998 U1 (LINEAR)
| Parameter |
Value |
| Designation |
C/1998 U1 (LINEAR) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
1998-05-02T12:00:10.497600Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:29:57Z |
| Obs used |
122 |
| NEO |
- |
| M1 |
9.500 |
| K1 |
10.000 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
1998-11-12.0000000 |
| e |
1.00043848 |
| q (au) |
3.975445 |
| a (au) |
-9066.409392 |
| i (deg) |
156.428505 |
| Ω (om, deg) |
210.457099 |
| ω (w, deg) |
124.645648 |
| M (ma, deg) |
0.000221 |
Magnitude
Scatter + Global Linear
$$
M_a = (12.169 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
12.169 |
| n |
2.000 |
| gf |
0.857 |
| gb |
-0.501 |
| k |
1.000 |
| δ90 |
2.868 |
| 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
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-02-03 00:00 |
20:28:53.32 |
-42:44:17.1 |
HIP 100941 |
12.15 |
| 2026-02-03 12:00 |
20:28:56.36 |
-42:44:11.8 |
HIP 100941 |
12.56 |
| 2026-02-04 00:00 |
20:28:59.40 |
-42:44:06.7 |
HIP 100941 |
12.98 |
| 2026-02-04 12:00 |
20:29:02.43 |
-42:44:01.8 |
HIP 101083 |
13.15 |
| 2026-02-05 00:00 |
20:29:05.45 |
-42:43:57.0 |
HIP 101083 |
13.05 |
| 2026-02-05 12:00 |
20:29:08.47 |
-42:43:52.3 |
HIP 101083 |
12.97 |
| 2026-02-06 00:00 |
20:29:11.49 |
-42:43:47.7 |
HIP 101083 |
12.91 |
| 2026-02-06 12:00 |
20:29:14.50 |
-42:43:43.3 |
HIP 101083 |
12.87 |
| 2026-02-07 00:00 |
20:29:17.50 |
-42:43:39.0 |
HIP 101083 |
12.85 |
| 2026-02-07 12:00 |
20:29:20.50 |
-42:43:34.9 |
HIP 101083 |
12.86 |
| 2026-02-08 00:00 |
20:29:23.49 |
-42:43:30.9 |
HIP 101083 |
12.89 |
| 2026-02-08 12:00 |
20:29:26.48 |
-42:43:27.0 |
HIP 101113 |
12.72 |
| 2026-02-09 00:00 |
20:29:29.45 |
-42:43:23.3 |
HIP 101113 |
12.52 |
| 2026-02-09 12:00 |
20:29:32.42 |
-42:43:19.7 |
HIP 101113 |
12.35 |
| 2026-02-10 00:00 |
20:29:35.39 |
-42:43:16.3 |
HIP 101113 |
12.21 |
| 2026-02-10 12:00 |
20:29:38.34 |
-42:43:13.0 |
HIP 101113 |
12.09 |
| 2026-02-11 00:00 |
20:29:41.29 |
-42:43:09.8 |
HIP 101113 |
11.99 |
| 2026-02-11 12:00 |
20:29:44.23 |
-42:43:06.8 |
HIP 101113 |
11.93 |
| 2026-02-12 00:00 |
20:29:47.16 |
-42:43:03.9 |
HIP 101113 |
11.89 |
| 2026-02-12 12:00 |
20:29:50.08 |
-42:43:01.1 |
HIP 101113 |
11.87 |
| 2026-02-13 00:00 |
20:29:53.00 |
-42:42:58.5 |
HIP 101113 |
11.89 |
| 2026-02-13 12:00 |
20:29:55.90 |
-42:42:56.1 |
HIP 101113 |
11.93 |
| 2026-02-14 00:00 |
20:29:58.80 |
-42:42:53.7 |
HIP 101113 |
11.99 |
| 2026-02-14 12:00 |
20:30:01.68 |
-42:42:51.6 |
HIP 101113 |
12.08 |
| 2026-02-15 00:00 |
20:30:04.56 |
-42:42:49.5 |
HIP 101113 |
12.20 |
| 2026-02-15 12:00 |
20:30:07.43 |
-42:42:47.6 |
HIP 101113 |
12.33 |
| 2026-02-16 00:00 |
20:30:10.28 |
-42:42:45.9 |
HIP 101113 |
12.49 |
| 2026-02-16 12:00 |
20:30:13.13 |
-42:42:44.3 |
HIP 101113 |
12.68 |
| 2026-02-17 00:00 |
20:30:15.97 |
-42:42:42.8 |
HIP 101113 |
12.88 |
| 2026-02-17 12:00 |
20:30:18.79 |
-42:42:41.5 |
HIP 101113 |
13.10 |
| 2026-02-18 00:00 |
20:30:21.61 |
-42:42:40.3 |
HIP 101113 |
13.34 |
| 2026-02-18 12:00 |
20:30:24.41 |
-42:42:39.3 |
HIP 101113 |
13.59 |
| 2026-02-19 00:00 |
20:30:27.20 |
-42:42:38.4 |
HIP 101113 |
13.86 |
| 2026-02-19 12:00 |
20:30:29.98 |
-42:42:37.7 |
HIP 101113 |
14.15 |
| 2026-02-20 00:00 |
20:30:32.75 |
-42:42:37.1 |
HIP 101113 |
14.44 |
| 2026-02-20 12:00 |
20:30:35.50 |
-42:42:36.6 |
HIP 101113 |
14.75 |
| 2026-02-21 00:00 |
20:30:38.24 |
-42:42:36.3 |
HIP 101113 |
15.07 |
| 2026-02-21 12:00 |
20:30:40.97 |
-42:42:36.1 |
HIP 101113 |
15.40 |
| 2026-02-22 00:00 |
20:30:43.69 |
-42:42:36.1 |
HIP 101113 |
15.74 |
| 2026-02-22 12:00 |
20:30:46.40 |
-42:42:36.3 |
HIP 101113 |
16.09 |
| 2026-02-23 00:00 |
20:30:49.09 |
-42:42:36.5 |
HIP 101113 |
16.45 |
| 2026-02-23 12:00 |
20:30:51.76 |
-42:42:36.9 |
HIP 101113 |
16.81 |
| 2026-02-24 00:00 |
20:30:54.43 |
-42:42:37.5 |
HIP 101113 |
17.18 |