| 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) |
| 2026-09-20 00:00 |
14:21:41.16 |
-52:14:29.9 |
HIP 70164 |
5.68 |
| 2026-09-20 12:00 |
14:21:43.64 |
-52:14:24.4 |
HIP 70164 |
5.97 |
| 2026-09-21 00:00 |
14:21:46.13 |
-52:14:19.1 |
HIP 70164 |
6.26 |
| 2026-09-21 12:00 |
14:21:48.64 |
-52:14:13.9 |
HIP 70164 |
6.57 |
| 2026-09-22 00:00 |
14:21:51.16 |
-52:14:09.0 |
HIP 70164 |
6.88 |
| 2026-09-22 12:00 |
14:21:53.70 |
-52:14:04.2 |
HIP 70164 |
7.21 |
| 2026-09-23 00:00 |
14:21:56.26 |
-52:13:59.5 |
HIP 70164 |
7.53 |
| 2026-09-23 12:00 |
14:21:58.83 |
-52:13:55.0 |
HIP 70164 |
7.87 |
| 2026-09-24 00:00 |
14:22:01.41 |
-52:13:50.7 |
HIP 70164 |
8.21 |
| 2026-09-24 12:00 |
14:22:04.02 |
-52:13:46.6 |
HIP 70164 |
8.56 |
| 2026-09-25 00:00 |
14:22:06.64 |
-52:13:42.6 |
HIP 70164 |
8.91 |
| 2026-09-25 12:00 |
14:22:09.27 |
-52:13:38.8 |
HIP 70164 |
9.27 |
| 2026-09-26 00:00 |
14:22:11.92 |
-52:13:35.2 |
HIP 70164 |
9.63 |
| 2026-09-26 12:00 |
14:22:14.58 |
-52:13:31.7 |
HIP 70164 |
9.99 |
| 2026-09-27 00:00 |
14:22:17.26 |
-52:13:28.4 |
HIP 70164 |
10.36 |
| 2026-09-27 12:00 |
14:22:19.95 |
-52:13:25.2 |
HIP 70164 |
10.73 |
| 2026-09-28 00:00 |
14:22:22.66 |
-52:13:22.3 |
HIP 70164 |
11.11 |
| 2026-09-28 12:00 |
14:22:25.38 |
-52:13:19.5 |
HIP 70164 |
11.49 |
| 2026-09-29 00:00 |
14:22:28.11 |
-52:13:16.8 |
HIP 70164 |
11.87 |
| 2026-09-29 12:00 |
14:22:30.86 |
-52:13:14.4 |
HIP 70164 |
12.25 |
| 2026-09-30 00:00 |
14:22:33.63 |
-52:13:12.1 |
HIP 70164 |
12.64 |
| 2026-09-30 12:00 |
14:22:36.40 |
-52:13:09.9 |
HIP 70164 |
13.03 |
| 2026-10-01 00:00 |
14:22:39.19 |
-52:13:08.0 |
HIP 70164 |
13.42 |
| 2026-10-01 12:00 |
14:22:41.99 |
-52:13:06.2 |
HIP 70164 |
13.82 |
| 2026-10-02 00:00 |
14:22:44.81 |
-52:13:04.6 |
HIP 70164 |
14.22 |
| 2026-10-02 12:00 |
14:22:47.64 |
-52:13:03.1 |
HIP 70164 |
14.62 |
| 2026-10-03 00:00 |
14:22:50.48 |
-52:13:01.8 |
HIP 70164 |
15.02 |
| 2026-10-03 12:00 |
14:22:53.33 |
-52:13:00.7 |
HIP 70164 |
15.43 |
| 2026-10-04 00:00 |
14:22:56.20 |
-52:12:59.8 |
HIP 70164 |
15.84 |
| 2026-10-04 12:00 |
14:22:59.08 |
-52:12:59.0 |
HIP 70164 |
16.25 |
| 2026-10-05 00:00 |
14:23:01.97 |
-52:12:58.4 |
HIP 70402 |
16.38 |
| 2026-10-05 12:00 |
14:23:04.87 |
-52:12:58.0 |
HIP 70402 |
16.10 |
| 2026-10-06 00:00 |
14:23:07.78 |
-52:12:57.7 |
HIP 70402 |
15.83 |
| 2026-10-06 12:00 |
14:23:10.71 |
-52:12:57.6 |
HIP 70402 |
15.55 |
| 2026-10-07 00:00 |
14:23:13.64 |
-52:12:57.7 |
HIP 70402 |
15.29 |
| 2026-10-07 12:00 |
14:23:16.59 |
-52:12:58.0 |
HIP 70402 |
15.02 |
| 2026-10-08 00:00 |
14:23:19.55 |
-52:12:58.4 |
HIP 70402 |
14.77 |
| 2026-10-08 12:00 |
14:23:22.51 |
-52:12:59.0 |
HIP 70402 |
14.52 |
| 2026-10-09 00:00 |
14:23:25.49 |
-52:12:59.8 |
HIP 70402 |
14.27 |
| 2026-10-09 12:00 |
14:23:28.48 |
-52:13:00.7 |
HIP 70402 |
14.04 |
| 2026-10-10 00:00 |
14:23:31.48 |
-52:13:01.8 |
HIP 70402 |
13.81 |
| 2026-10-10 12:00 |
14:23:34.49 |
-52:13:03.1 |
HIP 70402 |
13.59 |
| 2026-10-11 00:00 |
14:23:37.51 |
-52:13:04.6 |
HIP 70402 |
13.38 |