RASNZ Occultation Section - 2003 CO1 Occultation Update

ASTROMETRIC UPDATE:
OCCULTATION BY (120061) 2003 CO1 - 2012 APR 29

Event Rank : 1

(The event Rank is a measure of the likelihood of observing an event, and is equal to the probability of at least one successful observation by a team of two observers spaced 1/8 path width just inside opposite sides of the predicted path. An event rank of 100 indicates that the prediction is expected to be very accurate).

THE UPDATED PATH

Note: The duration given in the line below is the interval during which the occultation shadow sweeps across the Earth - please see the minute markers on the map to determine the approximate time for your location.

On 2012 Apr 29 UT, the 55 km diameter asteroid (120061) 2003 CO1 will occult a 13.0 mag star in the constellation Ophiuchus for observers along a very large uncertainty path that may cross Australia.

In the case of an occultation, the combined light of the asteroid and the star will drop by 7.2 mag to 20.2 mag (the magnitude of the asteroid) for at most 3.7 seconds.

This update is based on historical astrometry from the MPC files (via AstDys), and the following catalogs for the star position: UCAC.

Additional details of this and other events are available at Steve Preston's website at http://www.asteroidoccultation.com/

EVENT DETAILS SUMMARY :

Event Rank : 1
Date and approx. UT time of event : 2012 Apr 29, 19:57 - 2012 Apr 29, 20:00 UT
(Refer to map(s) for your own location)
Magnitude of target star : 13.0
Magnitude drop [mag] : 7.2
Estimated maximum duration [s] : 3.7
Phase of moon, angular distance : 55 % sunlit, 123° distance
Sun : 142° distance
Rough path description : possibly Australia

Data for the target star :

Name : UCAC2 23170662
Constellation : Ophiuchus
J2000 position with proper motion to date of event [h,m,s ; °,',"]: RA: 17 08 59.4051 DE: -21 44 35.273
Position source : mpos:UCAC2 pm:UCAC2
Standard error : RA,DE ["]: ( .161, .161 )
V mag [mag] : 13.0
B mag [mag] : 0.0
Remarks : (none)

Data for the minor planet :

Number, name : (120061) 2003 CO1
Approx. diameter [km] : 55
Approx. diameter [arcsec] : .006
Distance from Earth [AU] : 12.24000
Source of used astrometry : MPC (via Astdys)
Number of used observations : 157
Number of rejected observations : 4
Time covered by the observations : 2002 Feb 12 - 2010 Jun 13
1 sigma uncertainty ellipse (major, minor, PA) : 0.752, 0.126, 112°
Remarks : (none)
Orbital Elements for (120061) 2003 CO1 :
Update computed by : Steve Preston, Medina, Washington, USA. (OrbFit).

The Occultation Path :

Approximate projected width [km] : 155
Uncertainty interval [path widths] : +/- 64.19 (1 sigma)
Uncertainty interval [seconds] : +/- 389.6 (1 sigma)
Uncertainty interval approx RA,DE ["] : (+/- .720 +/- .335) (1 sigma)
Uncertainty ellipse (major, minor, PA) : ( .768", .203", 111° ) (1 sigma)
Approx speed of asteroid's shadow [km/s]: 14.6840
Important Note regarding Accuracy:
The uncertainty interval in path widths given above (and shown as a 1-sigma uncertainty ellipse on the plot) refers to RMS deviation and is applied as a +/- range. In other words, a path uncertainty of 1.0 path widths means that the actual center of the asteroid's shadow path should fall within plus or minus 1 path width of the plotted path center. However path errors larger than 1 sigma have been observed so observers should be alert for primary occultations within plus or minus 3 sigma of the updated path.
Further, almost all asteroidal satellites discovered so far have been found within 10 diameters of the asteroid (since this distance is deep enough within the gravitational well to be stable over long timescales). Therefore, if monitoring for secondary events, observing out to about 10 path-widths either side of the predicted track remains worthwhile.
We therefore recommend that you monitor for events if your observing location is up to +/- 10 path-widths from the predicted track. If not monitoring for occultations by secondary bodies you should observe from locations within 3 sigma of the nominal path.
In terms of time, the predictions are now usually accurate to about +/- 0.3 minute so you should be most attentive during the predicted minute of the event. However if intending to catch a potential satellite occultation you should start observing at least 10 times the predicted central duration before the predicted closest approach time for your location, and continue for a similar period afterwards.
Path Co-ordinates :

 Occultation of UCAC2 23170662 by 120061 2003 CO1 on 2012 Apr 29 
                   Centre              Star  Star   Sun     Path Limit1           Path Limit2           Error Limit1          Error Limit2
  E. Longitude    Latitude      U.T.    Alt   Az    Alt                                                                                       
      o  '  "     o  '  "    h  m  s     o     o     o    o  '  "    o  '  "    o  '  "    o  '  "    o  '  "    o  '  "    o  '  "    o  '  "
                                                         Longitude  Latitude   Longitude  Latitude   Longitude  Latitude   Longitude  Latitude
   -159  6 11   -77 15 17   19 57 36    19   254    -5 -155 44 26  -77  3 22 -162 25 35  -77 24 12  ... .. ..   .. .. ..  112 38 54  -42 52 10
   -159 23 53   -77 48 32   19 57 40    19   255    -5 -155 54 58  -77 36 56 -162 50 36  -77 57  6  ... .. ..   .. .. ..  111 55 27  -42 58 12
   -159 38 40   -78 21 32   19 57 44    19   255    -6 -156  1 49  -78 10 10 -163 13 29  -78 29 48  ... .. ..   .. .. ..  111 11 57  -43  4  5
   -159 50 13   -78 54 17   19 57 48    19   256    -6 -156  4 35  -78 43  5 -163 34  3  -79  2 18  ... .. ..   .. .. ..  110 28 23  -43  9 48
   -159 58 11   -79 26 49   19 57 52    19   256    -7 -156  2 49  -79 15 44 -163 52  2  -79 34 37  ... .. ..   .. .. ..  109 44 46  -43 15 22

   -160  2  5   -79 59  7   19 57 56    20   256    -7 -155 55 53  -79 48  6 -164  7  7  -80  6 46  ... .. ..   .. .. ..  109  1  5  -43 20 47
   -160  1 19   -80 31 14   19 58  0    20   256    -7 -155 43  4  -80 20 10 -164 18 52  -80 38 47  ... .. ..   .. .. ..  108 17 21  -43 26  3
   -159 55 11   -81  3  9   19 58  4    20   256    -8 -155 23 28  -80 51 58 -164 26 48  -81 10 39  ... .. ..   .. .. ..  107 33 33  -43 31 10
   -159 42 44   -81 34 51   19 58  8    20   256    -8 -154 55 58  -81 23 28 -164 30 15  -81 42 24  ... .. ..   .. .. ..  106 49 41  -43 36  8
   -159 22 49   -82  6 22   19 58 12    20   256    -9 -154 19 10  -81 54 40 -164 28 23  -82 14  1  ... .. ..   .. .. ..  106  5 45  -43 40 56

   -158 53 56   -82 37 39   19 58 16    20   256    -9 -153 31 17  -82 25 30 -164 20  6  -82 45 32  ... .. ..   .. .. ..  105 21 45  -43 45 35
   -158 14 10   -83  8 42   19 58 20    20   255    -9 -152 30  6  -82 55 58 -164  3 59  -83 16 55  ... .. ..   .. .. ..  104 37 41  -43 50  5
   -157 20 56   -83 39 29   19 58 24    20   255   -10 -151 12 44  -83 25 57 -163 38  6  -83 48 10  ... .. ..   .. .. ..  103 53 32  -43 54 26
   -156 10 54   -84  9 55   19 58 28    20   254   -10 -149 35 33  -83 55 24 -162 59 51  -84 19 15  ... .. ..   .. .. ..  103  9 20  -43 58 37
   -154 39 28   -84 39 57   19 58 32    20   252   -10 -147 33 47  -84 24  9 -162  5 34  -84 50 10  ... .. ..   .. .. ..  102 25  2  -44  2 39

   -152 40 24   -85  9 26   19 58 36    20   251   -11 -145  1 18  -84 52  2 -160 50  3  -85 20 49  ... .. ..   .. .. ..  101 40 40  -44  6 32
   -150  5  2   -85 38 13   19 58 40    20   248   -11 -141 50 15  -85 18 47 -159  5 41  -85 51  9  ... .. ..   .. .. ..  100 56 14  -44 10 15
   -146 41 16   -86  5 58   19 58 44    20   245   -11 -137 50 47  -85 44  1 -156 40 55  -86 20 58  ... .. ..   .. .. ..  100 11 42  -44 13 49
   -142 12 23   -86 32 18   19 58 48    20   241   -12 -132 51 12  -86  7 13 -153 17 46  -86 50  2  ... .. ..   .. .. ..   99 27  6  -44 17 13
   -136 15 59   -86 56 32   19 58 52    20   235   -12 -126 39 13  -86 27 41 -148 27 27  -87 17 54  ... .. ..   .. .. ..   98 42 24  -44 20 28

   -128 25 19   -87 17 40   19 58 56    20   227   -12 -119  5 18  -86 44 30 -141 23 55  -87 43 45  ... .. ..   .. .. ..   97 57 38  -44 23 33
   -118 17 22   -87 34 15   19 59  0    20   217   -12 -110  9 28  -86 56 34 -130 58 33  -88  6  6  ... .. ..   .. .. ..   97 12 46  -44 26 29
   -105 54 23   -87 44 29   19 59  4    20   205   -13 -100  9 27  -87  2 49 -115 59  1  -88 22 21  ... .. ..   .. .. ..   96 27 50  -44 29 15
   - 92 10 57   -87 46 45   19 59  8    19   192   -13 - 89 43 27  -87  2 30 - 96 46 52  -88 29  0  ... .. ..   .. .. ..   95 42 48  -44 31 51
Uncertainty in time = +/- 464 secs

Prediction of 2012 Mar 10.0

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