Titan.20200731

July 31, 2020

Prediction Last Updated: March 09, 2020

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Across the globe pictured, the three solid black lines correspond to the northern limit, centerline, and southern limit of the Titan’s shadow. The Northern and Southern limits correspond to a radius of 1288 km. The dashed lines indicate 3-sigma errors. The shaded area on the globe represents where the sun is more than 0 degrees below the horizon. The shadow paths on the globe are an approximation at the geocentric close approach time; they disregard the Earth rotation during the event.



Table 1: Prediction Details
Titan Geocentric Mid-time (hh:mm:ss)

July 31, 2020 00:03:42 ± 00:00:9. UT1

Prediction pred1.0_v1.0
Titan apparent magnitude 8.6
Occultation Star Gaia DR2 G magnitude 10.856917
Occultation Star Gaia DR2 rp magnitude 9.979922
Occultation Star Gaia DR2 bp magnitude 11.699285
Titan Minimum Geocentric Separation 0.0248 ± 0.0200 arcsec1
Position Angle (Titan relative to the star; measured north through east) -15.62
Moon 82% Moon, ~ 37 degrees away

1One standard deviation of random error




Table 2: Reference Star Position
Reference star position:
(Gaia DR2)
RA (h:m:s; J2000) Dec (d:m:s; J2000) Notes
Titan.20200731 (Catalog; 2015.5) 19:58:52.0614 -20:51:30.0023
Titan.20200731 (Catalog; epoch of occ) 19:58:52.0628 ± 0.0003 -20:51:30.0439 ± 0.0002
Titan.20200731 (Measured) - -

Potential Star Duplicity:

Unknown




Table 3: Projected KBO Offsets from Reference Ephemeris at the Time of the Event
Body RA (arcsec) Dec (arcsec)  
Titan

0 ± 0.0200

0 ± 0.0200 See Notes 5 and 6; Includes Titan Center of Light to Center of Body correction (if applicable)

2Measured position corresponds to RA offset of 0. and Dec. offset of 0.

3All "offsets" are degined 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.

4The reference positions for Titan are those given by JPL Horizon's ephemeris (Titan source file: JPL#SAT425l_merged_DE438 ; Earth center source file: DE438 )

5Data from various telescope were reduced with respect to the Gaia DR2 catalog. A model was developed to fit the residuals obtained from our measured positions compared to that of the object's JPL ephemeris. All residuals obtained from the different telescopes were consistent with the model. The model includes the first-order effects of errors in the orbital elements of the object: (i) constant offsets in RA and Dec, (ii) linear (in time) offsets in RA and Dec, and (iii) potential sinusoidal terms with companion's period. The model was propagated to obtain the predicted position and error of the KBO at the time of the occultation. The errors listed for the KBO are 1 standard deviation.




Table 4: Site Information
Site
East Longitude
Latitude

Site Altitude6

(km)

Distance7

(km)

Velocity

(km/s)

CTIO
-70 48 54
-30 09 54
2.215
793 S
14.84
Las Campanas
-70 42 00
-29 00 30
2.282
665 S
14.85
Geocentric
..........
..........
-6378.14
162 S
14.6

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

7"Distance" refers to the closest approach of the "Site" to the center of Titan's shadow in the shadow plane. The errors on all closest approach distances are ±131 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 Occultation Predictions for Individual Sites
Site
KBO Immersion (UT)8
UT Mid-Time
KBO Altitude

Solar Altitude8

KBO Emersion (UT)8

CTIO
00:08:23.702
00:09:32
36.45
-25.93
00:10:40.495
Las Campanas
00:08:18.759
00:09:33
36.45
-25.89
00:10:47.375
Geocentric
00:02:14.710
00:03:42
00:05:09.737

8The errors on all times are ± 0:9. (9. seconds; one standard deviation). The solar altitude is given for locations where it is relevant (solar altitude greater than -18 deg). No entry in the immersion and emersion columns indicates that the occultation is not predicted to be visible at that site.




Webpage generated by C. A. Zuluaga (czuluaga@mit.edu) on March 09, 2020

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

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