C/1999 E1 (Li)
| Parameter |
Value |
| Designation |
C/1999 E1 (Li) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
1999-01-31T18:43:25.651200Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:29:57Z |
| Obs used |
299 |
| NEO |
- |
| M1 |
10.600 |
| K1 |
4.500 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
1999-09-13.0000000 |
| e |
0.76010596 |
| q (au) |
3.920026 |
| a (au) |
16.340657 |
| i (deg) |
46.881232 |
| Ω (om, deg) |
127.834346 |
| ω (w, deg) |
329.768187 |
| M (ma, deg) |
3.345599 |
Magnitude
Scatter + Global Linear
$$
M_a = (9.991 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
9.991 |
| n |
2.000 |
| gf |
0.842 |
| gb |
-0.500 |
| k |
0.957 |
| 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
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-02-03 00:00 |
18:42:09.14 |
+02:25:31.3 |
HIP 91695 |
14.18 |
| 2026-02-03 12:00 |
18:42:12.89 |
+02:25:46.2 |
HIP 91695 |
14.70 |
| 2026-02-04 00:00 |
18:42:16.62 |
+02:26:01.4 |
HIP 91695 |
15.26 |
| 2026-02-04 12:00 |
18:42:20.33 |
+02:26:16.7 |
HIP 91695 |
15.86 |
| 2026-02-05 00:00 |
18:42:24.02 |
+02:26:32.2 |
HIP 91695 |
16.50 |
| 2026-02-05 12:00 |
18:42:27.70 |
+02:26:47.9 |
HIP 91695 |
17.17 |
| 2026-02-06 00:00 |
18:42:31.35 |
+02:27:03.8 |
HIP 91695 |
17.86 |
| 2026-02-06 12:00 |
18:42:34.98 |
+02:27:19.8 |
HIP 91695 |
18.58 |
| 2026-02-07 00:00 |
18:42:38.59 |
+02:27:36.0 |
HIP 91695 |
19.31 |
| 2026-02-07 12:00 |
18:42:42.18 |
+02:27:52.3 |
HIP 91695 |
20.06 |
| 2026-02-08 00:00 |
18:42:45.75 |
+02:28:08.8 |
HIP 91889 |
19.74 |
| 2026-02-08 12:00 |
18:42:49.29 |
+02:28:25.5 |
HIP 91889 |
18.83 |
| 2026-02-09 00:00 |
18:42:52.82 |
+02:28:42.4 |
HIP 91889 |
17.92 |
| 2026-02-09 12:00 |
18:42:56.32 |
+02:28:59.4 |
HIP 91889 |
17.02 |
| 2026-02-10 00:00 |
18:42:59.80 |
+02:29:16.6 |
HIP 91889 |
16.12 |
| 2026-02-10 12:00 |
18:43:03.26 |
+02:29:33.9 |
HIP 91889 |
15.23 |
| 2026-02-11 00:00 |
18:43:06.69 |
+02:29:51.4 |
HIP 91889 |
14.34 |
| 2026-02-11 12:00 |
18:43:10.10 |
+02:30:09.0 |
HIP 91889 |
13.46 |
| 2026-02-12 00:00 |
18:43:13.49 |
+02:30:26.8 |
HIP 91889 |
12.59 |
| 2026-02-12 12:00 |
18:43:16.86 |
+02:30:44.8 |
HIP 91889 |
11.72 |
| 2026-02-13 00:00 |
18:43:20.20 |
+02:31:02.9 |
HIP 91889 |
10.86 |
| 2026-02-13 12:00 |
18:43:23.52 |
+02:31:21.1 |
HIP 91889 |
10.01 |
| 2026-02-14 00:00 |
18:43:26.81 |
+02:31:39.5 |
HIP 91889 |
9.17 |
| 2026-02-14 12:00 |
18:43:30.08 |
+02:31:58.1 |
HIP 91889 |
8.34 |
| 2026-02-15 00:00 |
18:43:33.32 |
+02:32:16.8 |
HIP 91889 |
7.52 |
| 2026-02-15 12:00 |
18:43:36.54 |
+02:32:35.6 |
HIP 91889 |
6.72 |
| 2026-02-16 00:00 |
18:43:39.74 |
+02:32:54.6 |
HIP 91889 |
5.94 |
| 2026-02-16 12:00 |
18:43:42.90 |
+02:33:13.7 |
HIP 91889 |
5.18 |
| 2026-02-17 00:00 |
18:43:46.05 |
+02:33:33.0 |
HIP 91889 |
4.46 |
| 2026-02-17 12:00 |
18:43:49.16 |
+02:33:52.4 |
HIP 91889 |
3.80 |
| 2026-02-18 00:00 |
18:43:52.26 |
+02:34:12.0 |
HIP 91889 |
3.21 |
| 2026-02-18 12:00 |
18:43:55.32 |
+02:34:31.6 |
HIP 91889 |
2.76 |
| 2026-02-19 00:00 |
18:43:58.36 |
+02:34:51.4 |
HIP 91889 |
2.51 |
| 2026-02-19 12:00 |
18:44:01.37 |
+02:35:11.4 |
HIP 91889 |
2.52 |
| 2026-02-20 00:00 |
18:44:04.36 |
+02:35:31.4 |
HIP 91889 |
2.77 |
| 2026-02-20 12:00 |
18:44:07.31 |
+02:35:51.6 |
HIP 91889 |
3.21 |
| 2026-02-21 00:00 |
18:44:10.24 |
+02:36:12.0 |
HIP 91889 |
3.77 |
| 2026-02-21 12:00 |
18:44:13.15 |
+02:36:32.4 |
HIP 91889 |
4.39 |
| 2026-02-22 00:00 |
18:44:16.02 |
+02:36:53.0 |
HIP 91889 |
5.06 |
| 2026-02-22 12:00 |
18:44:18.87 |
+02:37:13.6 |
HIP 91889 |
5.76 |
| 2026-02-23 00:00 |
18:44:21.69 |
+02:37:34.4 |
HIP 91889 |
6.47 |
| 2026-02-23 12:00 |
18:44:24.48 |
+02:37:55.4 |
HIP 91889 |
7.19 |
| 2026-02-24 00:00 |
18:44:27.24 |
+02:38:16.4 |
HIP 91889 |
7.91 |