4179_Toutatis Planning

Background

Asteroid 4179 Toutatis (formerly 1989 AC) was discovered by C. Pollas on 4 Jan 1989 at Caussols, France, on photographic plates taken by Alain Maury and Derral Mulholland.

Click here to see Maury's web page on Toutatis' discovery, orbit, and name.


Toutatis Discovery Photograph


The asteroid's orbit has the lowest inclination to the ecliptic plane of any known Earth-crossing asteroid. It is in a 3:1 mean-motion resonance with Jupiter that serves as a dynamical pathway from main-belt orbits to Earth-crossing orbits on time scales of a million years. Toutatis may have the most chaotic orbit studied to date, a consequence of the asteroid's frequent close approaches to Earth.

Toutatis' approach to within 0.024 AU (9.4 lunar distances) on 8 Dec 1992 presented an unprecedented opportunity for radar investigation of a small body. The southerly declinations near closest approach made conditions more favorable for the fully steerable Goldstone Radar in California than for the Arecibo Observatory in Puerto Rico. Images placing hundreds to thousands of resolution cells on Toutatis were obtained at Goldstone daily during Dec. 2-18 and at Arecibo daily during Dec. 14-19. Because of the results from the 1992 radar experiment, our ephemeris and prior knowledge of the asteroid's echo signature are excellent. The goals in 1996 are to make high-resolution images that refine Scott Hudson's current model of the asteroid's shape and unusual spin state.

Click here for Scott Hudson's page on the expected progression of the delay-Doppler images, the plane-of-sky appearance of the current model, and the km/Hz conversion factor.



Toutatis Close Approaches (EMdist = Earth-Moon distances) 

Date        1992 Dec  8     1996 Nov 29     2000 Oct 31     2004 Sep 29
hh:mm             05:37           22:54           04:31           13:37

Dist AU    0.0241484197    0.0354303011    0.0738653055    0.0103592320 
     km       3,612,552       5,300,298      11,050,092       1,549,719
     miles    2,244,774       3,293,452       6,866,209         962,951
     EMdist         9.4            13.8            28.7             4.0

RA           13 17 41.8      13 35 28.3      14 32 12.3      14 31 33.2
Dec         -23 39 54.6     -21 43 27.8     -21 07 23.3     -59 40 29.9
Constell'n        Hydra           Virgo           Libra       Centaurus

SNR Calculation

 
Target Name:	4179_Toutatis
Source File:	4179_Toutatis.eph
Date:		Tue Nov  5 14:43:43 PST 1996
HMag:		-15.3
Diameter:	2.800
Period:		125		 
                                        Max          
                                 Date   run       
  Date     RA  Decl Delta  Runs   SNR   SNR 

1996 11 25 242 -30  0.043   177 11108   901
1996 11 26 234 -30  0.040   195 15241  1182
1996 11 27 225 -28  0.038   216 19624  1457
1996 11 28 216 -26  0.036   245 26135  1840
1996 11 29 207 -23  0.035   273 31685  2135
1996 11 30 198 -19  0.036   289 30813  2034
1996 12  1 189 -15  0.037   306 29961  1929
1996 12  2 182 -11  0.039   311 25817  1650
1996 12  3 175  -8  0.041   314 22273  1414

Goldstone Track Assignments

 
 
                UTC
1996   1996   TX window
DOY    Date   hhmm-hhmm        PST TX Window

330   Nov 25  1755-1950	      Mon   0955-1150
331   Nov 26  1715-1915	      Tues  0915-1115
332   Nov 27  1630-1830	      Wed   0830-1030
333   Nov 28  1530-1830	      Thurs 0730-1030
334   Nov 29  1435-1655	      Fri   0635-0855
335   Nov 30  1330-1650	      Sat   0530-0850
336   Dec  1  1230-1650	      Sun   0430-0850
337   Dec  2  1140-1645	      Mon   0340-0845
338   Dec  3  1050-1645	      Tues  0250-0845	 


Toutatis Transmit Windows

Uncertainties

 

1-sigma uncertainties on Nov 25 00:00 UTC are 2", 0.7 Hz, 115.2 usec

-- Jon Giorgini, Nov. 2, 1996


 
Setups

We plan to proceed through the following sequence on the first date:

        monostatic cw for about 20 minutes
	monostatic 11-usec ranging 
	monostatic imaging at 1/8 microseconds
	bistatic   imaging at 1/8 microseconds

Most of the experiment will be devoted to bistatic imaging.

Our tracks are very short and it is critical that we begin on time.

The initial cw setup will be:

   bandwidth:   1000 Hz  (sample interval: 10000 x 0.1 usec)

   frequencies:    2     (to give reduced data a 500-Hz window)

   FFT:         1024     (for 0.9765625-Hz resolution)
                         (VME should run FFT=4096, for 0.244-Hz res'n)
   dwell:         10 s  

____________________________________________________________________
RANGING SETUPS from Toutatis 1992: (code=255, FFT=256, 1 channel)
____________________________________________________________________
Setup     Baud   NACC       bandwidth  resolution   1/res'n   nom
                               Hz         Hz          sec     gate
____________________________________________________________________

TU1XS01   0.125    123      255.06      0.9963	      1.00    34
                   890       35.25      0.1377        7.26
                  1471       21.327     0.08331      12.00
                  2210       14.196     0.05545      18.03
                  2942       10.664     0.04166      24.01
                  3309        9.4810    0.03704      27.00
                  3700        8.4791    0.03312      30.19
                  7400        4.2395    0.01656      60.38
                 14800        2.1198    0.00828     120.77
                     
TU1XS02   0.25     123      127.5       0.498    
TU1XS04   0.500    307       25.5       0.100      
TU1XS08   1.000    153       25.6       0.100      
TU1XS16   2.000      4      490.2       1.915     
TU1XS32   4.000      2      490.2       1.915      
TU1XS33   4.125      2      475.3       1.857      
TU1XS80  10.000      1      392.2       1.532                 11      
TU1XS88  11.000      1      356.5       1.393                 11 


 
Instructions



TOUTATIS POINTING FOR ALL TRACKS


NOTES:  

THE DOY 330 (NOV 25) TRACK USED THESE SOLUTION 50 COORDINATES: 

Date (UTC)    DOY  hhmmss    RA       Dec         TX Offsets      RTT
                     
1996 Nov 25   330  180000  241.8294 -30.3956
1996 Nov 25   330  190000  241.5073 -30.3742    0.0039  0.0002   43.1
1996 Nov 25   330  200000  241.1826 -30.3503

THE DOY 331 (NOV 26) TRACK USED THESE SOLUTION 53 COORDINATES: 

Date (UTC)    DOY  hhmmss    RA       Dec         TX Offsets      RTT
1996 Nov 26   331  170000  234.2701 -29.6095  
1996 Nov 26   331  180000  233.9054 -29.5646    0.0041  0.0005   40.1
1996 Nov 26   331  193000  233.3533 -29.4917 


WE HAVE MADE A NEW SOLUTION (57).  

 The source files are on:  stealth:/data/osod/ops/4179_Toutatis/
                          intruder:/d1/rosema/4179_Toutatis/support/
		
 and include:  EPH.OUT.s57
               PRDX.OUT.14c-14v-13v.s57

Here is Solution 57 pointing for remaining tracks:

------------------------------------------------------------------------
Date (UTC)    DOY  hhmmss    RA       Dec         TX Offsets      RTT
                                                 LHA     Dec
1996 Nov 27   332  163000  225.6126 -28.1493 
1996 Nov 27   332  173000  225.2122 -28.0725    0.0042  0.0008   37.7
1996 Nov 27   332  183000  224.8096 -27.9925 

1996 Nov 28   333  153000  216.5194 -25.9546 
1996 Nov 28   333  170000  215.8915 -25.7880    0.0042  0.0011   36.1
1996 Nov 28   333  183000  215.2611 -25.6144  

1996 Nov 29   334  143000  207.2397 -23.0092
1996 Nov 29   334  160000  206.6175 -22.7982    0.0041  0.0014   35.4
1996 Nov 29   334  170000  206.2020 -22.6542 

1996 Nov 30   335  133000  198.2548 -19.4832 
1996 Nov 30   335  153000  197.4734 -19.1629    0.0039  0.0016   35.6
1996 Nov 30   335  173000  196.6941 -18.8355  

1996 Dec  1   336  123000  189.9590 -15.6679 
1996 Dec  1   336  150000  189.0773 -15.2541    0.0036  0.0017   36.7
1996 Dec  1   336  173000  188.2029 -14.8346 

1996 Dec  2   337  113000  182.5768 -11.8702 
1996 Dec  2   337  140000  181.8049 -11.4733    0.0033  0.0017   38.5
1996 Dec  2   337  163000  181.0384 -11.0753 

1996 Dec  3   338  110000  176.0347  -8.2476
1996 Dec  3   338  140000  175.2386  -7.8142    0.0031  0.0016   41.2
1996 Dec  3   338  170000  174.4537  -7.3835 





  Dr. Steven J. Ostro         |   PHONE:  (818) 354-3173
  300-233                     |   FAX:    (818) 354-9476
  Jet Propulsion Laboratory   |   email:  ostro@echo.jpl.nasa.gov
  Pasadena, CA 91109-8099
Asteroid Radar Astronomy