| 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) |
| 2026-05-12 00:00 |
18:44:54.71 |
+03:35:10.7 |
HIP 91893 |
20.07 |
| 2026-05-12 12:00 |
18:44:52.30 |
+03:35:26.1 |
HIP 91893 |
19.85 |
| 2026-05-13 00:00 |
18:44:49.86 |
+03:35:41.3 |
HIP 91893 |
19.64 |
| 2026-05-13 12:00 |
18:44:47.39 |
+03:35:56.4 |
HIP 91893 |
19.45 |
| 2026-05-14 00:00 |
18:44:44.89 |
+03:36:11.2 |
HIP 91893 |
19.27 |
| 2026-05-14 12:00 |
18:44:42.37 |
+03:36:25.9 |
HIP 91893 |
19.10 |
| 2026-05-15 00:00 |
18:44:39.81 |
+03:36:40.4 |
HIP 91893 |
18.96 |
| 2026-05-15 12:00 |
18:44:37.23 |
+03:36:54.7 |
HIP 91893 |
18.83 |
| 2026-05-16 00:00 |
18:44:34.63 |
+03:37:08.8 |
HIP 91893 |
18.72 |
| 2026-05-16 12:00 |
18:44:31.99 |
+03:37:22.7 |
HIP 91893 |
18.62 |
| 2026-05-17 00:00 |
18:44:29.33 |
+03:37:36.4 |
HIP 91838 |
18.36 |
| 2026-05-17 12:00 |
18:44:26.64 |
+03:37:49.9 |
HIP 91838 |
17.68 |
| 2026-05-18 00:00 |
18:44:23.93 |
+03:38:03.2 |
HIP 91838 |
16.98 |
| 2026-05-18 12:00 |
18:44:21.19 |
+03:38:16.4 |
HIP 91838 |
16.29 |
| 2026-05-19 00:00 |
18:44:18.42 |
+03:38:29.3 |
HIP 91838 |
15.60 |
| 2026-05-19 12:00 |
18:44:15.63 |
+03:38:42.0 |
HIP 91838 |
14.90 |
| 2026-05-20 00:00 |
18:44:12.81 |
+03:38:54.5 |
HIP 91838 |
14.20 |
| 2026-05-20 12:00 |
18:44:09.97 |
+03:39:06.8 |
HIP 91838 |
13.51 |
| 2026-05-21 00:00 |
18:44:07.11 |
+03:39:18.9 |
HIP 91838 |
12.82 |
| 2026-05-21 12:00 |
18:44:04.22 |
+03:39:30.8 |
HIP 91838 |
12.13 |
| 2026-05-22 00:00 |
18:44:01.30 |
+03:39:42.5 |
HIP 91838 |
11.45 |
| 2026-05-22 12:00 |
18:43:58.36 |
+03:39:54.0 |
HIP 91838 |
10.77 |
| 2026-05-23 00:00 |
18:43:55.40 |
+03:40:05.3 |
HIP 91838 |
10.10 |
| 2026-05-23 12:00 |
18:43:52.41 |
+03:40:16.3 |
HIP 91838 |
9.45 |
| 2026-05-24 00:00 |
18:43:49.40 |
+03:40:27.2 |
HIP 91838 |
8.81 |
| 2026-05-24 12:00 |
18:43:46.37 |
+03:40:37.8 |
HIP 91838 |
8.20 |
| 2026-05-25 00:00 |
18:43:43.32 |
+03:40:48.3 |
HIP 91838 |
7.62 |
| 2026-05-25 12:00 |
18:43:40.24 |
+03:40:58.5 |
HIP 91838 |
7.07 |
| 2026-05-26 00:00 |
18:43:37.14 |
+03:41:08.5 |
HIP 91838 |
6.57 |
| 2026-05-26 12:00 |
18:43:34.02 |
+03:41:18.2 |
HIP 91838 |
6.14 |
| 2026-05-27 00:00 |
18:43:30.88 |
+03:41:27.8 |
HIP 91838 |
5.79 |
| 2026-05-27 12:00 |
18:43:27.72 |
+03:41:37.1 |
HIP 91838 |
5.54 |
| 2026-05-28 00:00 |
18:43:24.53 |
+03:41:46.2 |
HIP 91838 |
5.40 |
| 2026-05-28 12:00 |
18:43:21.33 |
+03:41:55.1 |
HIP 91838 |
5.38 |
| 2026-05-29 00:00 |
18:43:18.10 |
+03:42:03.8 |
HIP 91838 |
5.49 |
| 2026-05-29 12:00 |
18:43:14.85 |
+03:42:12.3 |
HIP 91838 |
5.73 |
| 2026-05-30 00:00 |
18:43:11.59 |
+03:42:20.5 |
HIP 91838 |
6.07 |
| 2026-05-30 12:00 |
18:43:08.30 |
+03:42:28.5 |
HIP 91838 |
6.50 |
| 2026-05-31 00:00 |
18:43:04.99 |
+03:42:36.3 |
HIP 91838 |
7.02 |
| 2026-05-31 12:00 |
18:43:01.67 |
+03:42:43.9 |
HIP 91838 |
7.59 |
| 2026-06-01 00:00 |
18:42:58.33 |
+03:42:51.2 |
HIP 91838 |
8.22 |
| 2026-06-01 12:00 |
18:42:54.96 |
+03:42:58.3 |
HIP 91838 |
8.89 |
| 2026-06-02 00:00 |
18:42:51.58 |
+03:43:05.2 |
HIP 91838 |
9.60 |