| 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) |
| 2026-03-26 00:00 |
18:46:15.58 |
+03:01:38.6 |
HIP 92101 |
4.44 |
| 2026-03-26 12:00 |
18:46:16.35 |
+03:02:03.1 |
HIP 92101 |
4.86 |
| 2026-03-27 00:00 |
18:46:17.09 |
+03:02:27.6 |
HIP 92101 |
5.29 |
| 2026-03-27 12:00 |
18:46:17.79 |
+03:02:52.1 |
HIP 92101 |
5.72 |
| 2026-03-28 00:00 |
18:46:18.45 |
+03:03:16.6 |
HIP 92101 |
6.15 |
| 2026-03-28 12:00 |
18:46:19.08 |
+03:03:41.0 |
HIP 92101 |
6.58 |
| 2026-03-29 00:00 |
18:46:19.67 |
+03:04:05.5 |
HIP 92101 |
7.01 |
| 2026-03-29 12:00 |
18:46:20.23 |
+03:04:29.9 |
HIP 92101 |
7.43 |
| 2026-03-30 00:00 |
18:46:20.75 |
+03:04:54.3 |
HIP 92101 |
7.86 |
| 2026-03-30 12:00 |
18:46:21.24 |
+03:05:18.7 |
HIP 92101 |
8.28 |
| 2026-03-31 00:00 |
18:46:21.69 |
+03:05:43.1 |
HIP 92101 |
8.70 |
| 2026-03-31 12:00 |
18:46:22.10 |
+03:06:07.4 |
HIP 92101 |
9.12 |
| 2026-04-01 00:00 |
18:46:22.48 |
+03:06:31.7 |
HIP 92101 |
9.54 |
| 2026-04-01 12:00 |
18:46:22.82 |
+03:06:56.0 |
HIP 92101 |
9.95 |
| 2026-04-02 00:00 |
18:46:23.13 |
+03:07:20.3 |
HIP 92101 |
10.36 |
| 2026-04-02 12:00 |
18:46:23.40 |
+03:07:44.5 |
HIP 92101 |
10.77 |
| 2026-04-03 00:00 |
18:46:23.64 |
+03:08:08.7 |
HIP 92101 |
11.18 |
| 2026-04-03 12:00 |
18:46:23.84 |
+03:08:32.9 |
HIP 92101 |
11.58 |
| 2026-04-04 00:00 |
18:46:24.00 |
+03:08:57.0 |
HIP 92101 |
11.99 |
| 2026-04-04 12:00 |
18:46:24.13 |
+03:09:21.1 |
HIP 92101 |
12.38 |
| 2026-04-05 00:00 |
18:46:24.22 |
+03:09:45.2 |
HIP 92101 |
12.78 |
| 2026-04-05 12:00 |
18:46:24.28 |
+03:10:09.2 |
HIP 92101 |
13.18 |
| 2026-04-06 00:00 |
18:46:24.30 |
+03:10:33.1 |
HIP 92101 |
13.57 |
| 2026-04-06 12:00 |
18:46:24.28 |
+03:10:57.0 |
HIP 92101 |
13.96 |
| 2026-04-07 00:00 |
18:46:24.23 |
+03:11:20.9 |
HIP 92101 |
14.35 |
| 2026-04-07 12:00 |
18:46:24.14 |
+03:11:44.7 |
HIP 92101 |
14.74 |
| 2026-04-08 00:00 |
18:46:24.02 |
+03:12:08.5 |
HIP 92101 |
15.12 |
| 2026-04-08 12:00 |
18:46:23.86 |
+03:12:32.2 |
HIP 92101 |
15.51 |
| 2026-04-09 00:00 |
18:46:23.66 |
+03:12:55.9 |
HIP 92101 |
15.89 |
| 2026-04-09 12:00 |
18:46:23.43 |
+03:13:19.5 |
HIP 92101 |
16.27 |
| 2026-04-10 00:00 |
18:46:23.17 |
+03:13:43.0 |
HIP 92101 |
16.65 |
| 2026-04-10 12:00 |
18:46:22.87 |
+03:14:06.5 |
HIP 92101 |
17.03 |
| 2026-04-11 00:00 |
18:46:22.53 |
+03:14:29.9 |
HIP 92101 |
17.40 |
| 2026-04-11 12:00 |
18:46:22.15 |
+03:14:53.2 |
HIP 92101 |
17.78 |
| 2026-04-12 00:00 |
18:46:21.74 |
+03:15:16.5 |
HIP 92101 |
18.15 |
| 2026-04-12 12:00 |
18:46:21.30 |
+03:15:39.7 |
HIP 92101 |
18.53 |
| 2026-04-13 00:00 |
18:46:20.82 |
+03:16:02.8 |
HIP 92101 |
18.90 |
| 2026-04-13 12:00 |
18:46:20.30 |
+03:16:25.8 |
HIP 92101 |
19.27 |
| 2026-04-14 00:00 |
18:46:19.75 |
+03:16:48.8 |
HIP 92101 |
19.64 |
| 2026-04-14 12:00 |
18:46:19.16 |
+03:17:11.7 |
HIP 92101 |
20.01 |
| 2026-04-15 00:00 |
18:46:18.53 |
+03:17:34.5 |
HIP 92101 |
20.38 |
| 2026-04-15 12:00 |
18:46:17.87 |
+03:17:57.3 |
HIP 92101 |
20.76 |
| 2026-04-16 00:00 |
18:46:17.18 |
+03:18:19.9 |
HIP 92101 |
21.13 |