| 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) |
| 2026-07-29 00:00 |
18:35:42.72 |
+03:29:52.1 |
HIP 91259 |
24.98 |
| 2026-07-29 12:00 |
18:35:39.29 |
+03:29:32.0 |
HIP 91259 |
25.83 |
| 2026-07-30 00:00 |
18:35:35.88 |
+03:29:11.6 |
HIP 91072 |
25.91 |
| 2026-07-30 12:00 |
18:35:32.48 |
+03:28:51.1 |
HIP 91072 |
25.14 |
| 2026-07-31 00:00 |
18:35:29.11 |
+03:28:30.4 |
HIP 91072 |
24.39 |
| 2026-07-31 12:00 |
18:35:25.75 |
+03:28:09.5 |
HIP 91072 |
23.64 |
| 2026-08-01 00:00 |
18:35:22.42 |
+03:27:48.4 |
HIP 91072 |
22.90 |
| 2026-08-01 12:00 |
18:35:19.10 |
+03:27:27.1 |
HIP 91072 |
22.18 |
| 2026-08-02 00:00 |
18:35:15.80 |
+03:27:05.7 |
HIP 91072 |
21.47 |
| 2026-08-02 12:00 |
18:35:12.52 |
+03:26:44.0 |
HIP 91072 |
20.77 |
| 2026-08-03 00:00 |
18:35:09.26 |
+03:26:22.2 |
HIP 91072 |
20.09 |
| 2026-08-03 12:00 |
18:35:06.02 |
+03:26:00.2 |
HIP 91072 |
19.43 |
| 2026-08-04 00:00 |
18:35:02.80 |
+03:25:38.0 |
HIP 91072 |
18.78 |
| 2026-08-04 12:00 |
18:34:59.60 |
+03:25:15.6 |
HIP 91072 |
18.15 |
| 2026-08-05 00:00 |
18:34:56.42 |
+03:24:53.0 |
HIP 91072 |
17.54 |
| 2026-08-05 12:00 |
18:34:53.26 |
+03:24:30.3 |
HIP 91072 |
16.96 |
| 2026-08-06 00:00 |
18:34:50.13 |
+03:24:07.4 |
HIP 91072 |
16.40 |
| 2026-08-06 12:00 |
18:34:47.01 |
+03:23:44.3 |
HIP 91072 |
15.86 |
| 2026-08-07 00:00 |
18:34:43.92 |
+03:23:21.0 |
HIP 91072 |
15.35 |
| 2026-08-07 12:00 |
18:34:40.85 |
+03:22:57.6 |
HIP 91072 |
14.88 |
| 2026-08-08 00:00 |
18:34:37.80 |
+03:22:33.9 |
HIP 91072 |
14.43 |
| 2026-08-08 12:00 |
18:34:34.78 |
+03:22:10.2 |
HIP 91072 |
14.02 |
| 2026-08-09 00:00 |
18:34:31.78 |
+03:21:46.2 |
HIP 91072 |
13.65 |
| 2026-08-09 12:00 |
18:34:28.80 |
+03:21:22.1 |
HIP 91072 |
13.32 |
| 2026-08-10 00:00 |
18:34:25.84 |
+03:20:57.8 |
HIP 91072 |
13.03 |
| 2026-08-10 12:00 |
18:34:22.91 |
+03:20:33.4 |
HIP 91072 |
12.79 |
| 2026-08-11 00:00 |
18:34:20.01 |
+03:20:08.8 |
HIP 91072 |
12.60 |
| 2026-08-11 12:00 |
18:34:17.12 |
+03:19:44.0 |
HIP 91072 |
12.45 |
| 2026-08-12 00:00 |
18:34:14.26 |
+03:19:19.1 |
HIP 91072 |
12.35 |
| 2026-08-12 12:00 |
18:34:11.43 |
+03:18:54.0 |
HIP 91072 |
12.30 |
| 2026-08-13 00:00 |
18:34:08.62 |
+03:18:28.8 |
HIP 91072 |
12.30 |
| 2026-08-13 12:00 |
18:34:05.84 |
+03:18:03.4 |
HIP 91072 |
12.35 |
| 2026-08-14 00:00 |
18:34:03.08 |
+03:17:37.9 |
HIP 91072 |
12.44 |
| 2026-08-14 12:00 |
18:34:00.35 |
+03:17:12.2 |
HIP 91072 |
12.58 |
| 2026-08-15 00:00 |
18:33:57.65 |
+03:16:46.4 |
HIP 91072 |
12.76 |
| 2026-08-15 12:00 |
18:33:54.97 |
+03:16:20.5 |
HIP 91072 |
12.99 |
| 2026-08-16 00:00 |
18:33:52.32 |
+03:15:54.3 |
HIP 91072 |
13.25 |
| 2026-08-16 12:00 |
18:33:49.69 |
+03:15:28.1 |
HIP 91072 |
13.54 |
| 2026-08-17 00:00 |
18:33:47.09 |
+03:15:01.7 |
HIP 91072 |
13.87 |
| 2026-08-17 12:00 |
18:33:44.52 |
+03:14:35.2 |
HIP 91072 |
14.22 |
| 2026-08-18 00:00 |
18:33:41.98 |
+03:14:08.5 |
HIP 91072 |
14.61 |
| 2026-08-18 12:00 |
18:33:39.46 |
+03:13:41.8 |
HIP 91072 |
15.01 |
| 2026-08-19 00:00 |
18:33:36.97 |
+03:13:14.8 |
HIP 91072 |
15.44 |