Quaoar.20120710 Occultation July 10, 2012

(last updated 2012 06 01)

OBSERVER NOTES

 

Across the globe pictured above, the three solid lines correspond to the northern limit, centerline, and southern limit of Ixion's shadow. The northern and southern limits correspond to a radius of 500 km. The upper and lower dashed lines indicate 3-sigma errors. The shaded area represents where the sun is more than 12 degrees below the horizon.
Table 1: Prediction Details
Quaoar Geocentric Mid-time (yyyy month dd hh:mm:ss)

2012 July 10 08:21:04± 00:00:311 UT

Quaoar Minimum Geocentric Separation 0.065± 0.0161 arcsec
Position Angle (Quaoar relative to the star; measured north through east) –1.09545 degrees
Geocentric Velocity 22.87 km/sec
Occultation Star USNO-B Rmagnitude 15.92

1One standard deviation of random error.
2The UCAC bandpass (579-642nm) is between V and R.


Table 2: Reference Star Position
Reference star position:
(UCAC2, at epoch of event)
RA (h:m:s; J2000) Dec (d:m:s; J2000) Notes
Quaoar.20120710 Catalog 17 29 09.9733± 0.098 –15 22 47.800± 0.09
Quaoar.20120710 Measured3 17 29 09.9588± 0.005 –15 22 47.546± 0.003
From 3 USNO 61-inch Telescope frames
Table 3: Projected KBO Offsets from Reference Ephemeris at the Time of the Event
Body RA (arcsec) Dec (arcsec)  
Quaoar

–0.2927± 0.0022

–0.098± 0.016 See Notes 5 and 6

3Measured position corresponds to RA offset of –0.2109 and Dec. offset of +0.254.

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 Haumea are those given by JPL Horizon's ephemeris (Quaoar source file: JPL16; Earth center source file: DE405).

6Data from the USNO 61-inch, SMARTS 0.9m, and Lowell 42-inch telescopes over the span of 3 years were reduced with respect to stars in the UCAC2 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 Quaoar: (i) constant offsets in RA and Dec, (ii) linear (in time) offsets in RA and Dec, and (iii) sinusoidal terms with the Earth's orbital 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)

IRTF
-155 28 29
19 49 46
4.182
1692 N.
22.31
Lowell
-111 39 54
35 12 12
2.219
2558 N.
22.15
Magdalena Ridge Obs.
-107 11 05
33 58 36
2.22
2388 N.
22.14
McDonald Observatory
–104 01 21
30 40 17
2.08
2065 N.
22.13
Table Mountaint
-117 40 50
34 22 55
2.29
2590 N.
22.18
Geocenter
----------
---------
center of Earth
1978 S.
21.87

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 Haumea's shadow in the shadow plane. The errors on all closest approach distances are ±955 km (one standard deviation). "S." means the site is south of the center of Haumea's shadow. "N." means the site is north of the center of Haumea's shadow.

Table 5: Quaoar.20120710 Occultation Predictions for Individual Sites

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

KBO Emersion (UT)9

IRTF
-----------
08:21:20
55
-----------
-----------
Lowell
-----------
08:18:30
27
-----------
-----------
Magdalena Ridge Obs.
-----------
08:18:14
25
-----------
-----------
McDonald Observatory
-----------
08:17:58
26
-----------
-----------
Table Mountaint
-----------
08:18:48
31
-----------
-----------
Geocenter
-----------
08:21:04
-----------
-----------
-----------

9The errors on all times are ±0:31 (31 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) 2012-06-01 09:50

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