| 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) |
| 2026-03-26 00:00 |
09:06:26.06 |
-14:47:48.2 |
HIP 44639 |
9.58 |
| 2026-03-26 12:00 |
09:06:24.83 |
-14:47:31.9 |
HIP 44639 |
9.28 |
| 2026-03-27 00:00 |
09:06:23.62 |
-14:47:15.5 |
HIP 44639 |
9.00 |
| 2026-03-27 12:00 |
09:06:22.42 |
-14:46:59.1 |
HIP 44639 |
8.73 |
| 2026-03-28 00:00 |
09:06:21.24 |
-14:46:42.7 |
HIP 44639 |
8.47 |
| 2026-03-28 12:00 |
09:06:20.07 |
-14:46:26.3 |
HIP 44639 |
8.23 |
| 2026-03-29 00:00 |
09:06:18.91 |
-14:46:09.8 |
HIP 44639 |
8.00 |
| 2026-03-29 12:00 |
09:06:17.77 |
-14:45:53.4 |
HIP 44639 |
7.79 |
| 2026-03-30 00:00 |
09:06:16.64 |
-14:45:36.8 |
HIP 44639 |
7.60 |
| 2026-03-30 12:00 |
09:06:15.52 |
-14:45:20.3 |
HIP 44639 |
7.43 |
| 2026-03-31 00:00 |
09:06:14.42 |
-14:45:03.8 |
HIP 44639 |
7.27 |
| 2026-03-31 12:00 |
09:06:13.34 |
-14:44:47.2 |
HIP 44639 |
7.14 |
| 2026-04-01 00:00 |
09:06:12.27 |
-14:44:30.6 |
HIP 44639 |
7.03 |
| 2026-04-01 12:00 |
09:06:11.21 |
-14:44:14.0 |
HIP 44639 |
6.94 |
| 2026-04-02 00:00 |
09:06:10.16 |
-14:43:57.4 |
HIP 44639 |
6.87 |
| 2026-04-02 12:00 |
09:06:09.14 |
-14:43:40.8 |
HIP 44639 |
6.83 |
| 2026-04-03 00:00 |
09:06:08.12 |
-14:43:24.1 |
HIP 44639 |
6.80 |
| 2026-04-03 12:00 |
09:06:07.12 |
-14:43:07.5 |
HIP 44639 |
6.80 |
| 2026-04-04 00:00 |
09:06:06.14 |
-14:42:50.8 |
HIP 44639 |
6.83 |
| 2026-04-04 12:00 |
09:06:05.17 |
-14:42:34.2 |
HIP 44639 |
6.87 |
| 2026-04-05 00:00 |
09:06:04.22 |
-14:42:17.5 |
HIP 44639 |
6.94 |
| 2026-04-05 12:00 |
09:06:03.28 |
-14:42:00.8 |
HIP 44639 |
7.03 |
| 2026-04-06 00:00 |
09:06:02.35 |
-14:41:44.1 |
HIP 44639 |
7.13 |
| 2026-04-06 12:00 |
09:06:01.44 |
-14:41:27.4 |
HIP 44639 |
7.26 |
| 2026-04-07 00:00 |
09:06:00.55 |
-14:41:10.7 |
HIP 44639 |
7.40 |
| 2026-04-07 12:00 |
09:05:59.67 |
-14:40:54.0 |
HIP 44639 |
7.55 |
| 2026-04-08 00:00 |
09:05:58.80 |
-14:40:37.3 |
HIP 44639 |
7.72 |
| 2026-04-08 12:00 |
09:05:57.96 |
-14:40:20.6 |
HIP 44639 |
7.90 |
| 2026-04-09 00:00 |
09:05:57.12 |
-14:40:03.9 |
HIP 44639 |
8.10 |
| 2026-04-09 12:00 |
09:05:56.30 |
-14:39:47.2 |
HIP 44639 |
8.30 |
| 2026-04-10 00:00 |
09:05:55.50 |
-14:39:30.5 |
HIP 44639 |
8.52 |
| 2026-04-10 12:00 |
09:05:54.72 |
-14:39:13.8 |
HIP 44639 |
8.74 |
| 2026-04-11 00:00 |
09:05:53.94 |
-14:38:57.2 |
HIP 44639 |
8.97 |
| 2026-04-11 12:00 |
09:05:53.19 |
-14:38:40.5 |
HIP 44639 |
9.21 |
| 2026-04-12 00:00 |
09:05:52.45 |
-14:38:23.8 |
HIP 44639 |
9.46 |
| 2026-04-12 12:00 |
09:05:51.72 |
-14:38:07.2 |
HIP 44639 |
9.71 |
| 2026-04-13 00:00 |
09:05:51.02 |
-14:37:50.6 |
HIP 44639 |
9.96 |
| 2026-04-13 12:00 |
09:05:50.32 |
-14:37:33.9 |
HIP 44639 |
10.22 |
| 2026-04-14 00:00 |
09:05:49.65 |
-14:37:17.3 |
HIP 44639 |
10.48 |
| 2026-04-14 12:00 |
09:05:48.99 |
-14:37:00.8 |
HIP 44639 |
10.75 |
| 2026-04-15 00:00 |
09:05:48.34 |
-14:36:44.2 |
HIP 44639 |
11.01 |
| 2026-04-15 12:00 |
09:05:47.71 |
-14:36:27.6 |
HIP 44639 |
11.28 |
| 2026-04-16 00:00 |
09:05:47.10 |
-14:36:11.1 |
HIP 44639 |
11.56 |