| Parameter |
Value |
| Designation |
C/1987 P1 (Bradfield) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
1987-11-07T06:34:43.440960Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:29:33Z |
| Obs used |
611 |
| NEO |
- |
| M1 |
6.000 |
| K1 |
8.500 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
1987-11-29.0000000 |
| e |
0.99473713 |
| q (au) |
0.868956 |
| a (au) |
165.110625 |
| i (deg) |
34.088067 |
| Ω (om, deg) |
268.092924 |
| ω (w, deg) |
73.899611 |
| M (ma, deg) |
0.010093 |
Magnitude
Scatter + Global Linear
$$
M_a = (5.750 + 2.678\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
5.750 |
| n |
2.678 |
| gf |
0.800 |
| gb |
-0.500 |
| k |
1.000 |
| 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
Residuals (Piecewise)
$$\epsilon = a \log_{10} r_{\mathrm{au}} + b$$
| Start (UTC) |
End (UTC) |
a |
b |
| 1987-08-12 |
1987-11-06 |
+1.8670 |
+0.018 |
| 1987-11-07 |
1987-12-09 |
+1.4060 |
+0.081 |
| 1987-12-09 |
1988-03-08 |
-0.4160 |
+0.009 |
| 1988-03-08 |
1988-04-11 |
+8.3598 |
-2.815 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-06-01 00:00 |
09:06:00.43 |
-14:14:54.0 |
HIP 44639 |
33.02 |
| 2026-06-01 12:00 |
09:06:01.30 |
-14:14:44.2 |
HIP 44639 |
33.20 |
| 2026-06-02 00:00 |
09:06:02.18 |
-14:14:34.5 |
HIP 44639 |
33.38 |
| 2026-06-02 12:00 |
09:06:03.08 |
-14:14:24.9 |
HIP 44639 |
33.57 |
| 2026-06-03 00:00 |
09:06:04.00 |
-14:14:15.4 |
HIP 44639 |
33.75 |
| 2026-06-03 12:00 |
09:06:04.92 |
-14:14:06.1 |
HIP 44639 |
33.94 |
| 2026-06-04 00:00 |
09:06:05.86 |
-14:13:56.9 |
HIP 44639 |
34.12 |
| 2026-06-04 12:00 |
09:06:06.82 |
-14:13:47.7 |
HIP 44859 |
33.97 |
| 2026-06-05 00:00 |
09:06:07.79 |
-14:13:38.7 |
HIP 44859 |
33.72 |
| 2026-06-05 12:00 |
09:06:08.77 |
-14:13:29.8 |
HIP 44859 |
33.46 |
| 2026-06-06 00:00 |
09:06:09.76 |
-14:13:21.1 |
HIP 44859 |
33.20 |
| 2026-06-06 12:00 |
09:06:10.77 |
-14:13:12.4 |
HIP 44859 |
32.94 |
| 2026-06-07 00:00 |
09:06:11.79 |
-14:13:03.9 |
HIP 44859 |
32.68 |
| 2026-06-07 12:00 |
09:06:12.83 |
-14:12:55.5 |
HIP 44859 |
32.41 |
| 2026-06-08 00:00 |
09:06:13.88 |
-14:12:47.2 |
HIP 44859 |
32.14 |
| 2026-06-08 12:00 |
09:06:14.94 |
-14:12:39.0 |
HIP 44859 |
31.87 |
| 2026-06-09 00:00 |
09:06:16.02 |
-14:12:31.0 |
HIP 44859 |
31.59 |
| 2026-06-09 12:00 |
09:06:17.11 |
-14:12:23.0 |
HIP 44859 |
31.31 |
| 2026-06-10 00:00 |
09:06:18.21 |
-14:12:15.2 |
HIP 44859 |
31.03 |
| 2026-06-10 12:00 |
09:06:19.32 |
-14:12:07.6 |
HIP 44859 |
30.75 |
| 2026-06-11 00:00 |
09:06:20.45 |
-14:12:00.0 |
HIP 44859 |
30.46 |
| 2026-06-11 12:00 |
09:06:21.59 |
-14:11:52.6 |
HIP 44859 |
30.17 |
| 2026-06-12 00:00 |
09:06:22.75 |
-14:11:45.2 |
HIP 44859 |
29.88 |
| 2026-06-12 12:00 |
09:06:23.91 |
-14:11:38.1 |
HIP 44859 |
29.59 |
| 2026-06-13 00:00 |
09:06:25.09 |
-14:11:31.0 |
HIP 44859 |
29.29 |
| 2026-06-13 12:00 |
09:06:26.28 |
-14:11:24.1 |
HIP 44859 |
28.99 |
| 2026-06-14 00:00 |
09:06:27.48 |
-14:11:17.2 |
HIP 44859 |
28.69 |
| 2026-06-14 12:00 |
09:06:28.70 |
-14:11:10.6 |
HIP 44859 |
28.39 |
| 2026-06-15 00:00 |
09:06:29.93 |
-14:11:04.0 |
HIP 44859 |
28.08 |
| 2026-06-15 12:00 |
09:06:31.17 |
-14:10:57.6 |
HIP 44859 |
27.77 |
| 2026-06-16 00:00 |
09:06:32.42 |
-14:10:51.3 |
HIP 44859 |
27.46 |
| 2026-06-16 12:00 |
09:06:33.69 |
-14:10:45.1 |
HIP 44859 |
27.15 |
| 2026-06-17 00:00 |
09:06:34.96 |
-14:10:39.1 |
HIP 44859 |
26.83 |
| 2026-06-17 12:00 |
09:06:36.25 |
-14:10:33.2 |
HIP 44859 |
26.51 |
| 2026-06-18 00:00 |
09:06:37.55 |
-14:10:27.4 |
HIP 44859 |
26.19 |
| 2026-06-18 12:00 |
09:06:38.86 |
-14:10:21.7 |
HIP 44859 |
25.87 |
| 2026-06-19 00:00 |
09:06:40.18 |
-14:10:16.2 |
HIP 44859 |
25.54 |
| 2026-06-19 12:00 |
09:06:41.52 |
-14:10:10.8 |
HIP 44859 |
25.22 |
| 2026-06-20 00:00 |
09:06:42.86 |
-14:10:05.6 |
HIP 44859 |
24.88 |
| 2026-06-20 12:00 |
09:06:44.22 |
-14:10:00.4 |
HIP 44859 |
24.55 |
| 2026-06-21 00:00 |
09:06:45.58 |
-14:09:55.5 |
HIP 44859 |
24.22 |
| 2026-06-21 12:00 |
09:06:46.96 |
-14:09:50.6 |
HIP 44859 |
23.88 |
| 2026-06-22 00:00 |
09:06:48.35 |
-14:09:45.9 |
HIP 44859 |
23.54 |