| Parameter |
Value |
| Designation |
C/1999 A1 (Tilbrook) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
1999-01-29T15:46:41.666880Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:29:57Z |
| Obs used |
68 |
| NEO |
- |
| M1 |
14.300 |
| K1 |
10.000 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
1999-01-20.0000000 |
| e |
0.99589489 |
| q (au) |
0.730741 |
| a (au) |
178.007719 |
| i (deg) |
89.481788 |
| Ω (om, deg) |
259.123002 |
| ω (w, deg) |
232.669862 |
| M (ma, deg) |
359.995992 |
Magnitude
Scatter + Global Linear
$$
M_a = (13.200 + 2.643\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
13.200 |
| n |
2.643 |
| gf |
0.800 |
| gb |
-1.000 |
| k |
0.800 |
| δ90 |
10.000 |
| 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 |
17:23:16.17 |
+17:03:18.6 |
HIP 85096 |
9.72 |
| 2026-07-29 12:00 |
17:23:14.40 |
+17:03:04.3 |
HIP 85096 |
9.65 |
| 2026-07-30 00:00 |
17:23:12.64 |
+17:02:49.9 |
HIP 85096 |
9.61 |
| 2026-07-30 12:00 |
17:23:10.90 |
+17:02:35.4 |
HIP 85096 |
9.58 |
| 2026-07-31 00:00 |
17:23:09.18 |
+17:02:20.7 |
HIP 85096 |
9.58 |
| 2026-07-31 12:00 |
17:23:07.47 |
+17:02:05.8 |
HIP 85096 |
9.59 |
| 2026-08-01 00:00 |
17:23:05.77 |
+17:01:50.8 |
HIP 85096 |
9.63 |
| 2026-08-01 12:00 |
17:23:04.09 |
+17:01:35.7 |
HIP 85096 |
9.68 |
| 2026-08-02 00:00 |
17:23:02.43 |
+17:01:20.4 |
HIP 85096 |
9.75 |
| 2026-08-02 12:00 |
17:23:00.79 |
+17:01:05.0 |
HIP 85096 |
9.84 |
| 2026-08-03 00:00 |
17:22:59.16 |
+17:00:49.5 |
HIP 85096 |
9.95 |
| 2026-08-03 12:00 |
17:22:57.54 |
+17:00:33.8 |
HIP 85096 |
10.07 |
| 2026-08-04 00:00 |
17:22:55.95 |
+17:00:18.0 |
HIP 85096 |
10.21 |
| 2026-08-04 12:00 |
17:22:54.37 |
+17:00:02.1 |
HIP 85096 |
10.36 |
| 2026-08-05 00:00 |
17:22:52.80 |
+16:59:46.0 |
HIP 85096 |
10.53 |
| 2026-08-05 12:00 |
17:22:51.26 |
+16:59:29.7 |
HIP 85096 |
10.70 |
| 2026-08-06 00:00 |
17:22:49.73 |
+16:59:13.4 |
HIP 85096 |
10.89 |
| 2026-08-06 12:00 |
17:22:48.21 |
+16:58:56.9 |
HIP 85096 |
11.10 |
| 2026-08-07 00:00 |
17:22:46.72 |
+16:58:40.3 |
HIP 85096 |
11.31 |
| 2026-08-07 12:00 |
17:22:45.24 |
+16:58:23.6 |
HIP 85096 |
11.53 |
| 2026-08-08 00:00 |
17:22:43.78 |
+16:58:06.7 |
HIP 85096 |
11.76 |
| 2026-08-08 12:00 |
17:22:42.33 |
+16:57:49.7 |
HIP 85096 |
11.99 |
| 2026-08-09 00:00 |
17:22:40.91 |
+16:57:32.6 |
HIP 85096 |
12.24 |
| 2026-08-09 12:00 |
17:22:39.50 |
+16:57:15.4 |
HIP 85096 |
12.49 |
| 2026-08-10 00:00 |
17:22:38.11 |
+16:56:58.0 |
HIP 85096 |
12.74 |
| 2026-08-10 12:00 |
17:22:36.74 |
+16:56:40.5 |
HIP 85096 |
13.00 |
| 2026-08-11 00:00 |
17:22:35.39 |
+16:56:22.9 |
HIP 85096 |
13.27 |
| 2026-08-11 12:00 |
17:22:34.05 |
+16:56:05.2 |
HIP 85096 |
13.54 |
| 2026-08-12 00:00 |
17:22:32.73 |
+16:55:47.4 |
HIP 85096 |
13.82 |
| 2026-08-12 12:00 |
17:22:31.44 |
+16:55:29.4 |
HIP 85096 |
14.09 |
| 2026-08-13 00:00 |
17:22:30.16 |
+16:55:11.4 |
HIP 85096 |
14.37 |
| 2026-08-13 12:00 |
17:22:28.89 |
+16:54:53.2 |
HIP 85096 |
14.66 |
| 2026-08-14 00:00 |
17:22:27.65 |
+16:54:34.9 |
HIP 85096 |
14.94 |
| 2026-08-14 12:00 |
17:22:26.43 |
+16:54:16.5 |
HIP 85096 |
15.23 |
| 2026-08-15 00:00 |
17:22:25.22 |
+16:53:58.0 |
HIP 85096 |
15.52 |
| 2026-08-15 12:00 |
17:22:24.04 |
+16:53:39.4 |
HIP 84938 |
15.56 |
| 2026-08-16 00:00 |
17:22:22.87 |
+16:53:20.7 |
HIP 84938 |
15.15 |
| 2026-08-16 12:00 |
17:22:21.72 |
+16:53:01.9 |
HIP 84938 |
14.74 |
| 2026-08-17 00:00 |
17:22:20.60 |
+16:52:43.0 |
HIP 84938 |
14.34 |
| 2026-08-17 12:00 |
17:22:19.49 |
+16:52:24.0 |
HIP 84938 |
13.93 |
| 2026-08-18 00:00 |
17:22:18.40 |
+16:52:04.9 |
HIP 84938 |
13.53 |
| 2026-08-18 12:00 |
17:22:17.33 |
+16:51:45.7 |
HIP 84938 |
13.13 |
| 2026-08-19 00:00 |
17:22:16.28 |
+16:51:26.4 |
HIP 84938 |
12.74 |