1991 VH planning

Radar observations of (35107) 1991 VH

J. L. Margot, P. A. Taylor, M. Nolan, E. Howell, S. J. Ostro, L. A. M. Benner, J. D. Giorgini, C. Magri, L. Carter

Observations of (35107) 1991 VH in 2008 provide an exceptional opportunity to characterize the dynamics, morphology, and physical properties of a binary (or multiple) system. High resolution images obtained over a suitable range of aspect angles will provide detailed information on the regolith, size, shape, and spin of the components and on their mutual orbit and dynamical interactions. Unless the secondary is exceptionally symmetric (equatorial radii within 10% of each other), we expect it to be attitude unstable and therefore a challenge for shape reconstruction efforts. But we like challenges and we will try hard to characterize the rotation of the secondary.

In conjunction with pre-existing observations, these data will probe the formation and evolution of binaries in great detail, including dynamical processes such as tidal interactions and tumbling, radiative processes such as YORP, and erosional processes such as avalanches and lofting/redeposition of material. The signal-to-noise ratio will approach 1000 per run, allowing very high quality images to be obtained down to 8 m resolution. If the observations are successful 1991 VH may become one of the very best characterized binaries in the solar system, comparable to 1999 KW4.


We use Universal Time (UT) everywhere in this document. To obtain local time at Arecibo (AST), subtract 4. To obtain local time at Goldstone (PDT), subtract 7.

Arecibo schedule

UT Date         RTT     DEC    UT rise-set  runs   SNR/run (updated)
-----------------------------------------------------------
2008 JUL 29     86.4     37    22:18-23:22    22    101    1 x CW, 3 x 2 us, 7 x 0.1 us, azimuth arm fault
2008 AUG 01     75.8     32    21:23-23:24    48    160    2 x 3 x CW, 3 x 2 us, 34 x 0.5 us 
2008 AUG 03     69.1     29    20:52-23:16    62    220    3 x 0.5 us in last 6 minutes (vacion interlock missing, no radar technician on site, both drove in)
2008 AUG 05     62.8     24    20:23-23:02    76    306    
2008 AUG 07     57.1     19    19:58-22:42    86    425
2008 AUG 09     52.3     12    19:39-22:11    87    577
2008 AUG 10     50.3      8    19:34-21:50    81    660
2008 AUG 11     48.6      4    19:34-21:22    66    743
2008 AUG 12     47.2      0    19:49-20:38    31    818

Goldstone schedule

DOY   UT date   ---  UT window  ---   RTT  SNR/run
219 2008 AUG 06 0125 0255 0625 0655    62   31
220 2008 AUG 07 0125 0255 0545 0615    59   37
224 2008 AUG 11 2300 0030 0415 0510    48   64   Radiation clearance granted
Radiation clearance
 219 AUG-06-08  0255Z  0625Z    (LOCAL AUG. 05, 7:55PM TO 11:25PM PDT)
 220 AUG-07-08  0255Z  0545Z    (LOCAL AUG. 06, 7:55PM TO 10:45PM PDT)
!225 AUG-12-08  0030Z  0415Z    (LOCAL AUG. 11, 5:30PM TO 9:15PM PDT)
! = conflict to be resolved

Setup files

Arecibo setup files are in
/share/obs4/usr/radar/1991VH
Data reduction scripts are stored in :
/proj/radar/1991VH

Ephemerides are available in:

 
/share/trabuco4/jplephem/osod/ops/a35107
aardvark:/export/data3/osod/ops/a35107
Jon prepared solution 157, which we used on 2008 July 29. Jean-Luc obtained three range measurements on July 29 and generated solution 159, which we used on 2008 August 1. We found the object within a few us of the expected location. We will continue to use solution 159 on August 3, 5, and possibly longer, depending on how much drift we observe in upcoming tracks.

Expected uncertainties

Relevant 3-sigma uncertainties are listed below:

 
 Date__(UT)__HR:MN   POS (asec)   Doppler (Hz)  RTT (seconds)
 2008-Jul-29 00:00   .524         0.10          0.000337       Based on soln 157.
 2008-Aug-01 00:00   .493         0.08          0.000012       Based on soln 159.
 2008-Aug-03 00:00   .548         0.08          0.000021       Based on soln 159.

Expected bandwidth

The primary component is ~1.2 km in diameter and spins with 2.62 hours period (Pravec et al., 2006), so we expect a limb-to-limb bandwidth of ~13 Hz.

The secondary is likely ~500 m in diameter and may spin with 12.84 hours period (Pravec et al., 2006), so the limb-to-limb bandwidth would be ~1 Hz.

Expected phase coverage

Rotational coverage of the primary will be excellent as it spins with a period of 2.62 hours according to measurements by Pravec et al. The expected phase coverage for the mutual orbit is shown below with an arbitrary zero phase.

2008 Jul 29 - Arecibo

This is a very short track (less than an hour) with multiple objectives.

1. We will start with one CW run to confirm detection.

2. A single run with 8191 code at 2 us baud and 2 samples per baud (10 Hz tx offset, 61 Hz bandwidth, 32-point FFT) will allow us to compute a preliminary range measurement and determine whether the system is double or triple.

3. A single run with 1023 code at 2 us baud and 2 samples per baud (10 Hz tx offset, 489 Hz bandwidth, 32-point FFT) will confirm the range measurement above, at which point one observer will update the ephemeris and the other will recable for PFS sampling.

4. The rest of the track will be conducted with 65535 code at 0.1 us baud.

2008 Aug 01 - Arecibo

Objectives for this two-hour long track are as follows:

1. We will start with three CW runs to verify echo strength, measure primary and secondary bandwidths, and estimate cross-sections.

2. We will then acquire three runs with 1023 code at 2 us baud and 2 samples per baud (10 Hz tx offset, 61 Hz bandwidth, 128-point FFT) to confirm ephemeris solution 159.

3. We will acquire plenty of imaging data at 0.5 us baud. (8191 code, 1 sample per baud, 2 Hz tx offset, 244 Hz bandwidth, 512-point FFT).

4. We will end with three CW runs to verify echo strength, measure primary and secondary bandwidths, and estimate cross-sections.

2008 Aug 03 - Arecibo

Objectives for this 2.25 h track are to obtain at least four sequences of:

1. Four CW runs (10 min).

2. Twelve runs (28 min) at 0.5 us baud. (8191 code, 1 sample per baud, 2 Hz tx offset, 244 Hz bandwidth, 1024-point FFT).

2008 Aug 05 - Arecibo

Objectives for this 2h40m track are to obtain at least four sequences of:

1. Five CW runs (10 min).

2. Twelve runs (25 min) at 0.5 us baud. (8191 code, 1 sample per baud, 2 Hz tx offset, 244 Hz bandwidth, 1024-point FFT).

2009 Aug 06 - DOY 219 - Goldstone

Instructions for this track will be provided on the basis of the Arecibo results.

We will be doing mostly CW in a fixed configuration: no hopping, 2000 Hz receive offset. PFS will sample at 2 MHz with 0.5 MHz Faraday filter. What is critical is to measure limb-to-limb bandwidths with quasi continuous sampling to establish the rotation state of the secondary.

We will also obtain a few images for primary-secondary delay-Doppler separation measurements. We will use a 1 us baud, 4095 code, no coherent averaging, 245 Hz bandwidth, 256 FFT.

We will alternate between the following setups:

1. Twenty CW runs (40 min).

2. Ten imaging runs (20 min).

Pointing macros:

   UT               RA       DEC      dRA    dDEC
                    (deg)    (deg)    (mdeg) (mdeg)
2008 AUG 06 03:00  213.317  23.5950   1.3    -1.9
2008 AUG 06 05:00  213.156  23.3763   1.3    -1.9
2008 AUG 06 07:00  213.003  23.1540   1.2    -1.9

2009 Aug 07 - DOY 220 - Goldstone

Same configuration as DOY 219.

Pointing macros:

   UT               RA       DEC      dRA    dDEC
                    (deg)    (deg)    (mdeg) (mdeg)
2008 AUG 07 02:00  211.576  21.0204   1.5  -2.0
2008 AUG 07 04:00  211.403  20.7810   1.4  -2.0
2008 AUG 07 06:00  211.236  20.5374   1.4  -2.0

2008 Aug 07 - Arecibo

Objectives for this 2h44m track are to obtain at least four sequences of:

1. Five CW runs (10 min).

2. Twelve runs (23 min) at 0.2 us baud. (65535 code, 2 samples per baud, 2 Hz tx offset, 76 Hz bandwidth, 1024-point FFT).

2008 Aug 11 - Arecibo

Alternate between:

1. Two CW runs.

2. Twelve runs (19 min) at 0.1 us baud. (65535 code, 2 Hz tx offset, 152 Hz bandwidth, 256-point FFT).

2009 Aug 11 - DOY 224 - Goldstone

Same configuration as DOY 219. If there are any uncertainties about pointing, shift the balance to more CW and monitor signal strength carefully in real-time.

We will alternate between the following setups:

1. Twenty CW runs (32 min).

2. Ten imaging runs (16 min).

Pointing macros:

   UT               RA       DEC      dRA    dDEC
                    (deg)    (deg)    (mdeg) (mdeg)
2008 AUG 12 00:00  200.671   3.4258   1.6  -2.4
2008 AUG 12 02:00  200.435   3.0639   1.5  -2.4
2008 AUG 12 04:00  200.203   2.6998   1.5  -2.4

Contact information

                 Name            Institution     Work phone      Cell phone      Email
--------------------------------------------------------------------------------------------------------------
PI               Jean-Luc Margot Cornell         607 255 1810    607 229 5015    jlm@astro.cornell.edu
Rising star      Patrick Taylor  Cornell         607 255 2727                    ptaylor@astro.cornell.edu
 
AO guru/friend   Mike Nolan      NAIC            787 878 2612 x 334              nolan@naic.edu
DSN guru/friend  Lance Benner    JPL             818 354 7412    626 319 4369    lance.benner@jpl.nasa.gov

TX clearance     Reid Drummond   GDSCC           760 255 8218                    rdrummond@jgld.gdscc.nasa.gov
TX clearance     Larry Sturgis   GDSCC           760 255 8071                    LSturgis@jgld.gdscc.nasa.gov

DSN operator     J. Van Brimmer  RARG/ADVDEV     760 255 8469                    JVanbrimmer@gdscc.nasa.gov
DSN operator     M. Silva        RARG/ADVDEV     760 255 8469                    masilva@gdscc.nasa.gov
DSN 		 L. Juare	 RARG/ADVDEV	 760 255 8469                    LJuare@gdscc.nasa.gov

Ephemerides      Jon Giorgini    JPL             818 393 3107                    jdg@tycho.jpl.nasa.gov
GSSR support     Joseph Jao      JPL             818 354 2102    818 640 5802    Joseph.S.Jao@jpl.nasa.gov

How to reach people at Arecibo and Goldstone

JLM in Arecibo Control Room     787 878 2612 x 229
JLM VSQ                         787 878 2612 x 374
Patrick VSQ                     787 878 2612 x 379


JPL radar central               818 354 2877
Goldstone Pedestal              760 255 8470,8469,8259

Who will be where

In addition to our antenna and transmitter experts:
   
                Arecibo        Cornell      Goldstone         JPL         
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2008 JUL 29     Jean-Luc/Mike  Patrick                                 
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2008 AUG 01     Jean-Luc/Mike  
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2008 AUG 03     Jean-Luc
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2008 AUG 05     Patrick/Mike   Jean-Luc	                                    
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2008 AUG 06 G                  	           Jerry/Marc        Lance/Joseph
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2008 AUG 07 G                  	           Jerry/Marc        Lance/Joseph
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2008 AUG 07     Patrick/Mike   Jean-Luc	                                    
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2008 AUG 09     Patrick/Mike   Jean-Luc	                                    
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2008 AUG 10     Patrick/Mike   Jean-Luc	                                    
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2008 AUG 11     Patrick/Mike   Jean-Luc	                                    
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2008 AUG 12     Patrick/Mike   Jean-Luc	                                    
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jlm@astro.cornell.edu