| Parameter |
Value |
| Designation |
C/1999 S2 (McNaught-Watson) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
1997-11-22T14:49:59.252160Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:30:02Z |
| Obs used |
88 |
| NEO |
- |
| M1 |
8.000 |
| K1 |
4.500 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2000-03-17.0000000 |
| e |
1.00527083 |
| q (au) |
6.467743 |
| a (au) |
-1227.083165 |
| i (deg) |
65.820220 |
| Ω (om, deg) |
74.460976 |
| ω (w, deg) |
223.497414 |
| M (ma, deg) |
0.019384 |
Magnitude
Scatter + Global Linear
$$
M_a = (12.224 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
12.224 |
| n |
2.000 |
| gf |
0.977 |
| gb |
-0.827 |
| k |
0.800 |
| δ90 |
9.955 |
| 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) |
| 2026-06-01 00:00 |
04:51:31.00 |
+22:14:24.4 |
HIP 22715 |
21.67 |
| 2026-06-01 12:00 |
04:51:33.66 |
+22:14:31.4 |
HIP 22715 |
21.06 |
| 2026-06-02 00:00 |
04:51:36.32 |
+22:14:38.4 |
HIP 22715 |
20.44 |
| 2026-06-02 12:00 |
04:51:38.98 |
+22:14:45.3 |
HIP 22715 |
19.83 |
| 2026-06-03 00:00 |
04:51:41.65 |
+22:14:52.3 |
HIP 22715 |
19.22 |
| 2026-06-03 12:00 |
04:51:44.31 |
+22:14:59.2 |
HIP 22715 |
18.61 |
| 2026-06-04 00:00 |
04:51:46.98 |
+22:15:06.2 |
HIP 22715 |
18.00 |
| 2026-06-04 12:00 |
04:51:49.64 |
+22:15:13.1 |
HIP 22715 |
17.39 |
| 2026-06-05 00:00 |
04:51:52.31 |
+22:15:20.1 |
HIP 22715 |
16.78 |
| 2026-06-05 12:00 |
04:51:54.98 |
+22:15:27.0 |
HIP 22715 |
16.17 |
| 2026-06-06 00:00 |
04:51:57.64 |
+22:15:34.0 |
HIP 22715 |
15.57 |
| 2026-06-06 12:00 |
04:52:00.31 |
+22:15:40.9 |
HIP 22715 |
14.97 |
| 2026-06-07 00:00 |
04:52:02.97 |
+22:15:47.8 |
HIP 22715 |
14.37 |
| 2026-06-07 12:00 |
04:52:05.64 |
+22:15:54.8 |
HIP 22715 |
13.77 |
| 2026-06-08 00:00 |
04:52:08.30 |
+22:16:01.7 |
HIP 22715 |
13.17 |
| 2026-06-08 12:00 |
04:52:10.96 |
+22:16:08.6 |
HIP 22715 |
12.58 |
| 2026-06-09 00:00 |
04:52:13.63 |
+22:16:15.5 |
HIP 22715 |
11.99 |
| 2026-06-09 12:00 |
04:52:16.29 |
+22:16:22.4 |
HIP 22715 |
11.41 |
| 2026-06-10 00:00 |
04:52:18.95 |
+22:16:29.3 |
HIP 22715 |
10.83 |
| 2026-06-10 12:00 |
04:52:21.60 |
+22:16:36.2 |
HIP 22715 |
10.26 |
| 2026-06-11 00:00 |
04:52:24.26 |
+22:16:43.0 |
HIP 22715 |
9.69 |
| 2026-06-11 12:00 |
04:52:26.91 |
+22:16:49.9 |
HIP 22715 |
9.14 |
| 2026-06-12 00:00 |
04:52:29.57 |
+22:16:56.8 |
HIP 22715 |
8.59 |
| 2026-06-12 12:00 |
04:52:32.22 |
+22:17:03.6 |
HIP 22715 |
8.05 |
| 2026-06-13 00:00 |
04:52:34.86 |
+22:17:10.5 |
HIP 22715 |
7.53 |
| 2026-06-13 12:00 |
04:52:37.51 |
+22:17:17.3 |
HIP 22715 |
7.03 |
| 2026-06-14 00:00 |
04:52:40.15 |
+22:17:24.1 |
HIP 22715 |
6.54 |
| 2026-06-14 12:00 |
04:52:42.79 |
+22:17:30.9 |
HIP 22715 |
6.09 |
| 2026-06-15 00:00 |
04:52:45.42 |
+22:17:37.8 |
HIP 22715 |
5.66 |
| 2026-06-15 12:00 |
04:52:48.05 |
+22:17:44.5 |
HIP 22715 |
5.27 |
| 2026-06-16 00:00 |
04:52:50.68 |
+22:17:51.3 |
HIP 22715 |
4.93 |
| 2026-06-16 12:00 |
04:52:53.30 |
+22:17:58.1 |
HIP 22715 |
4.65 |
| 2026-06-17 00:00 |
04:52:55.92 |
+22:18:04.9 |
HIP 22715 |
4.44 |
| 2026-06-17 12:00 |
04:52:58.54 |
+22:18:11.6 |
HIP 22715 |
4.30 |
| 2026-06-18 00:00 |
04:53:01.15 |
+22:18:18.4 |
HIP 22715 |
4.25 |
| 2026-06-18 12:00 |
04:53:03.76 |
+22:18:25.1 |
HIP 22715 |
4.29 |
| 2026-06-19 00:00 |
04:53:06.36 |
+22:18:31.8 |
HIP 22715 |
4.42 |
| 2026-06-19 12:00 |
04:53:08.96 |
+22:18:38.6 |
HIP 22715 |
4.62 |
| 2026-06-20 00:00 |
04:53:11.55 |
+22:18:45.3 |
HIP 22715 |
4.89 |
| 2026-06-20 12:00 |
04:53:14.14 |
+22:18:51.9 |
HIP 22715 |
5.22 |
| 2026-06-21 00:00 |
04:53:16.72 |
+22:18:58.6 |
HIP 22715 |
5.60 |
| 2026-06-21 12:00 |
04:53:19.29 |
+22:19:05.3 |
HIP 22715 |
6.01 |
| 2026-06-22 00:00 |
04:53:21.86 |
+22:19:11.9 |
HIP 22715 |
6.45 |