| 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 |
0.846 |
| 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) |
| 2026-09-20 00:00 |
18:32:02.63 |
+02:41:30.1 |
HIP 90895 |
15.13 |
| 2026-09-20 12:00 |
18:32:02.26 |
+02:40:58.9 |
HIP 90895 |
15.65 |
| 2026-09-21 00:00 |
18:32:01.92 |
+02:40:27.8 |
HIP 90895 |
16.16 |
| 2026-09-21 12:00 |
18:32:01.62 |
+02:39:56.6 |
HIP 90895 |
16.67 |
| 2026-09-22 00:00 |
18:32:01.36 |
+02:39:25.5 |
HIP 90895 |
17.17 |
| 2026-09-22 12:00 |
18:32:01.13 |
+02:38:54.3 |
HIP 90895 |
17.68 |
| 2026-09-23 00:00 |
18:32:00.94 |
+02:38:23.2 |
HIP 90895 |
18.18 |
| 2026-09-23 12:00 |
18:32:00.78 |
+02:37:52.1 |
HIP 90895 |
18.68 |
| 2026-09-24 00:00 |
18:32:00.66 |
+02:37:21.0 |
HIP 90895 |
19.18 |
| 2026-09-24 12:00 |
18:32:00.57 |
+02:36:49.9 |
HIP 90895 |
19.67 |
| 2026-09-25 00:00 |
18:32:00.52 |
+02:36:18.9 |
HIP 90895 |
20.17 |
| 2026-09-25 12:00 |
18:32:00.51 |
+02:35:47.8 |
HIP 90895 |
20.66 |
| 2026-09-26 00:00 |
18:32:00.53 |
+02:35:16.8 |
HIP 90895 |
21.15 |
| 2026-09-26 12:00 |
18:32:00.58 |
+02:34:45.8 |
HIP 90895 |
21.64 |
| 2026-09-27 00:00 |
18:32:00.68 |
+02:34:14.9 |
HIP 90895 |
22.12 |
| 2026-09-27 12:00 |
18:32:00.80 |
+02:33:43.9 |
HIP 90895 |
22.61 |
| 2026-09-28 00:00 |
18:32:00.97 |
+02:33:13.0 |
HIP 90895 |
23.09 |
| 2026-09-28 12:00 |
18:32:01.17 |
+02:32:42.1 |
HIP 90895 |
23.57 |
| 2026-09-29 00:00 |
18:32:01.40 |
+02:32:11.3 |
HIP 90895 |
24.05 |
| 2026-09-29 12:00 |
18:32:01.67 |
+02:31:40.5 |
HIP 90895 |
24.53 |
| 2026-09-30 00:00 |
18:32:01.97 |
+02:31:09.7 |
HIP 90895 |
25.01 |
| 2026-09-30 12:00 |
18:32:02.32 |
+02:30:39.0 |
HIP 90895 |
25.49 |
| 2026-10-01 00:00 |
18:32:02.69 |
+02:30:08.3 |
HIP 90895 |
25.96 |
| 2026-10-01 12:00 |
18:32:03.10 |
+02:29:37.7 |
HIP 90895 |
26.44 |
| 2026-10-02 00:00 |
18:32:03.55 |
+02:29:07.1 |
HIP 90895 |
26.91 |
| 2026-10-02 12:00 |
18:32:04.04 |
+02:28:36.5 |
HIP 90895 |
27.39 |
| 2026-10-03 00:00 |
18:32:04.56 |
+02:28:06.0 |
HIP 90895 |
27.86 |
| 2026-10-03 12:00 |
18:32:05.11 |
+02:27:35.6 |
HIP 90895 |
28.33 |
| 2026-10-04 00:00 |
18:32:05.70 |
+02:27:05.2 |
HIP 90895 |
28.80 |
| 2026-10-04 12:00 |
18:32:06.33 |
+02:26:34.8 |
HIP 90895 |
29.27 |
| 2026-10-05 00:00 |
18:32:06.99 |
+02:26:04.6 |
HIP 90895 |
29.74 |
| 2026-10-05 12:00 |
18:32:07.68 |
+02:25:34.3 |
HIP 90895 |
30.21 |
| 2026-10-06 00:00 |
18:32:08.42 |
+02:25:04.2 |
HIP 90895 |
30.68 |
| 2026-10-06 12:00 |
18:32:09.19 |
+02:24:34.1 |
HIP 90895 |
31.15 |
| 2026-10-07 00:00 |
18:32:09.99 |
+02:24:04.0 |
HIP 90895 |
31.62 |
| 2026-10-07 12:00 |
18:32:10.83 |
+02:23:34.1 |
HIP 90895 |
32.09 |
| 2026-10-08 00:00 |
18:32:11.70 |
+02:23:04.2 |
HIP 90895 |
32.56 |
| 2026-10-08 12:00 |
18:32:12.61 |
+02:22:34.3 |
HIP 90895 |
33.03 |
| 2026-10-09 00:00 |
18:32:13.56 |
+02:22:04.6 |
HIP 91048 |
33.43 |
| 2026-10-09 12:00 |
18:32:14.54 |
+02:21:34.9 |
HIP 91048 |
33.34 |
| 2026-10-10 00:00 |
18:32:15.55 |
+02:21:05.3 |
HIP 90985 |
32.93 |
| 2026-10-10 12:00 |
18:32:16.60 |
+02:20:35.8 |
HIP 90985 |
32.38 |
| 2026-10-11 00:00 |
18:32:17.69 |
+02:20:06.3 |
HIP 90985 |
31.82 |