| Parameter |
Value |
| Designation |
C/1989 T1 (Helin-Roman-Alu) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
1989-12-15T22:37:06.297600Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:29:38Z |
| Obs used |
120 |
| NEO |
- |
| M1 |
12.500 |
| K1 |
13.750 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
1989-11-17.0000000 |
| e |
0.99061399 |
| q (au) |
1.047319 |
| a (au) |
111.582949 |
| i (deg) |
46.036538 |
| Ω (om, deg) |
8.519172 |
| ω (w, deg) |
68.125993 |
| M (ma, deg) |
359.975798 |
Magnitude
Scatter + Global Linear
$$
M_a = (10.273 + 3.956\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
10.273 |
| n |
3.956 |
| gf |
1.000 |
| gb |
-0.500 |
| k |
1.000 |
| 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
Residuals (Piecewise)
$$\epsilon = a \log_{10} r_{\mathrm{au}} + b$$
| Start (UTC) |
End (UTC) |
a |
b |
| 1989-10-01 |
1989-12-07 |
+5.1672 |
-0.345 |
| 1989-12-16 |
1990-11-17 |
-15.8129 |
+1.431 |
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 |
14:29:08.11 |
-53:28:31.4 |
HIP 70903 |
10.05 |
| 2026-03-26 12:00 |
14:29:05.41 |
-53:28:37.1 |
HIP 70903 |
10.27 |
| 2026-03-27 00:00 |
14:29:02.70 |
-53:28:42.6 |
HIP 70903 |
10.51 |
| 2026-03-27 12:00 |
14:28:59.97 |
-53:28:47.9 |
HIP 70903 |
10.76 |
| 2026-03-28 00:00 |
14:28:57.23 |
-53:28:53.0 |
HIP 70903 |
11.02 |
| 2026-03-28 12:00 |
14:28:54.47 |
-53:28:58.0 |
HIP 70903 |
11.30 |
| 2026-03-29 00:00 |
14:28:51.69 |
-53:29:02.8 |
HIP 70903 |
11.59 |
| 2026-03-29 12:00 |
14:28:48.90 |
-53:29:07.4 |
HIP 70903 |
11.89 |
| 2026-03-30 00:00 |
14:28:46.09 |
-53:29:11.8 |
HIP 70903 |
12.20 |
| 2026-03-30 12:00 |
14:28:43.27 |
-53:29:16.0 |
HIP 70903 |
12.52 |
| 2026-03-31 00:00 |
14:28:40.43 |
-53:29:20.0 |
HIP 70903 |
12.85 |
| 2026-03-31 12:00 |
14:28:37.58 |
-53:29:23.9 |
HIP 70903 |
13.19 |
| 2026-04-01 00:00 |
14:28:34.71 |
-53:29:27.5 |
HIP 70903 |
13.54 |
| 2026-04-01 12:00 |
14:28:31.83 |
-53:29:31.0 |
HIP 70903 |
13.89 |
| 2026-04-02 00:00 |
14:28:28.93 |
-53:29:34.3 |
HIP 70903 |
14.26 |
| 2026-04-02 12:00 |
14:28:26.02 |
-53:29:37.4 |
HIP 70903 |
14.63 |
| 2026-04-03 00:00 |
14:28:23.10 |
-53:29:40.3 |
HIP 70903 |
15.00 |
| 2026-04-03 12:00 |
14:28:20.16 |
-53:29:43.1 |
HIP 70699 |
15.11 |
| 2026-04-04 00:00 |
14:28:17.22 |
-53:29:45.6 |
HIP 70699 |
14.97 |
| 2026-04-04 12:00 |
14:28:14.25 |
-53:29:48.0 |
HIP 70699 |
14.83 |
| 2026-04-05 00:00 |
14:28:11.28 |
-53:29:50.2 |
HIP 70699 |
14.70 |
| 2026-04-05 12:00 |
14:28:08.29 |
-53:29:52.2 |
HIP 70699 |
14.57 |
| 2026-04-06 00:00 |
14:28:05.29 |
-53:29:54.0 |
HIP 70699 |
14.46 |
| 2026-04-06 12:00 |
14:28:02.28 |
-53:29:55.6 |
HIP 70699 |
14.36 |
| 2026-04-07 00:00 |
14:27:59.26 |
-53:29:57.0 |
HIP 70699 |
14.26 |
| 2026-04-07 12:00 |
14:27:56.22 |
-53:29:58.3 |
HIP 70699 |
14.18 |
| 2026-04-08 00:00 |
14:27:53.18 |
-53:29:59.3 |
HIP 70699 |
14.11 |
| 2026-04-08 12:00 |
14:27:50.12 |
-53:30:00.2 |
HIP 70699 |
14.05 |
| 2026-04-09 00:00 |
14:27:47.05 |
-53:30:00.9 |
HIP 70699 |
14.00 |
| 2026-04-09 12:00 |
14:27:43.97 |
-53:30:01.4 |
HIP 70699 |
13.96 |
| 2026-04-10 00:00 |
14:27:40.89 |
-53:30:01.7 |
HIP 70699 |
13.93 |
| 2026-04-10 12:00 |
14:27:37.79 |
-53:30:01.8 |
HIP 70699 |
13.92 |
| 2026-04-11 00:00 |
14:27:34.68 |
-53:30:01.7 |
HIP 70699 |
13.92 |
| 2026-04-11 12:00 |
14:27:31.56 |
-53:30:01.5 |
HIP 70699 |
13.93 |
| 2026-04-12 00:00 |
14:27:28.43 |
-53:30:01.0 |
HIP 70699 |
13.95 |
| 2026-04-12 12:00 |
14:27:25.30 |
-53:30:00.4 |
HIP 70699 |
13.98 |
| 2026-04-13 00:00 |
14:27:22.15 |
-53:29:59.5 |
HIP 70699 |
14.03 |
| 2026-04-13 12:00 |
14:27:19.00 |
-53:29:58.5 |
HIP 70699 |
14.09 |
| 2026-04-14 00:00 |
14:27:15.83 |
-53:29:57.3 |
HIP 70530 |
13.94 |
| 2026-04-14 12:00 |
14:27:12.66 |
-53:29:55.9 |
HIP 70530 |
13.48 |
| 2026-04-15 00:00 |
14:27:09.49 |
-53:29:54.4 |
HIP 70530 |
13.01 |
| 2026-04-15 12:00 |
14:27:06.30 |
-53:29:52.6 |
HIP 70530 |
12.54 |
| 2026-04-16 00:00 |
14:27:03.11 |
-53:29:50.7 |
HIP 70530 |
12.07 |