Titan.20180718 Occultation July 18, 2018

(last updated 2018 05 15)

 

Across the globe pictured above, the three solid lines correspond to the northern limit, centerline, and southern limit of Titan's shadow. The northern and southern limits correspond to a radius of 2576 km. The upper and lower dashed lines indicate 3-sigma errors. The shaded area represents where the sun is more than 0 degrees below the horizon.
Table 1: Prediction Details
Titan Geocentric Mid-time (yyyy month dd hh:mm:ss)

2018 July 18 15:10:11 UT

Titan Minimum Geocentric Separation 0.041 arcsec
Position Angle (Titanrelative to the star; measured north through east) 174.106 degrees
Geocentric Velocity 22.52 km/sec
Occultation Star Gaia DR2 magnitude 13.4227085

1One standard deviation of random error.


Table 2: Reference Star Position
Reference star position:
(Gaia DR2, at epoch of event)
RA (h:m:s; J2000) Dec (d:m:s; J2000) Notes
Titan.20180718 Catalog 18 17 53.2715 ± 0.2 mas –22 34 35.741 ± 0.1 mas
Gaia DR2 position with proper motion
     
Table 3: Projected Titan Offsets from Reference Ephemeris at the Time of the Event
Body RA (arcsec) Dec (arcsec)  
Titan

+0.0 ± 0.

+0.0 ± 0.0 JPL SAT389

3Measured position corresponds to RA offset of +0.0 and Dec. offset of +0.0.

4All "offsets" are defined in the ("corrected" – "reference") or ("observed" – "calculated") sense. The offsets should be added to reference positions to get the measured positions, which we use to calculate the prediction.

4Data analyzed using UCAC2 reference network. A weighted average of the data from the two telescopes was used to calculate the RA and DEC. The errors given are 1 standard deviation.

5The reference positions for Titan are those given by JPL Horizon's ephemeris (Titan source file: SAT389).

 

Table 4: Site Information

Site
East Longitude
Latitude

Site Altitude6

(km)

Distance7

(km)

Velocity

(km/s)

Hobart
+147 26 24
–42 48 18
0.043
2528 S.
22.52
Mt. John
+170 27 50
–43 59 22
1.041
3276 S.
22.69
Mt. Stromlo
+149 00 17
–35 19 12
0.77
1848 S.
22.82
Siding Spring
+149 03 44
–31 16 17
1.205
1445 S.
22.84
Zadko Telescope
+115 42 49
–31 21 24
0.05
732 S.
22.92
Geocenter
----------
---------
center of Earth
273 N.
22.52

6Altitude of each observatory is measured in kilometers above sea level.

7"Distance" refers to the closest approach distance of the "Site" to the center of Titan's shadow in the shadow plane. The errors on all closest approach distances are ±0 km (one standard deviation). "S." means the site is south of the center of Titan's shadow. "N." means the site is north of the center of Titan's shadow.

Table 5: Titan.20180718 Occultation Predictions for Individual Sites

Site
Titan Immersion (UT)9
UT Mid-Time
Titan Altitude
Solar Altitude9

TitanEmersion (UT)9

Hobart
15:07:59
15:08:20
54
–65
15:08:42
Mt. John
-----------
15:07:31
37
–52
-----------
Mt. Stromlo
15:06:40
15:07:59
54
–70
15:09:17
Siding Spring
15:06:17
15:07:50
55
–73
15:09:24
Zadko Telescope
15:08:08
15:09:55
80
–70
15:11:43
Geocenter
15:08:17
15:10:11
-----------
-----------
15:12:05

9The errors on all times are ±0:0 (0 seconds; one standard deviation). The solar altitude is given for locations where it is relevant (solar altitude greater than -18°). No entry in the immersion and emersion columns indicates that the occultation is not predicted to be visible at that site.


Last updated by Carlos Zuluaga (czuluaga@mit.edu) 2018-05-15 19:36 UT

Please direct all inquiries to PAL (planetary-astronomy@mit.edu)