Goldstone Radar Observations Planning: 2021 LD1


Background


2021 LD1    
2021 LD1 was discovered on June 2, 2021 by the NEOWISE spacecraft.
This object makes a relatively distant approach at 0.065 au (or ~25 lunar distances) on July 9, 2021.
The NEOWISE team (J. Masiero, personal comm.) reported a diameter of ~750 m  and a low optical albedo of ~0.05.
The NEOWISE observations also suggest that the object is elongated. No other physical properties
are known at this time.  2021 LD1 will be a moderately strong radar target unless its rotation period is slow.

2021 LD1 orbit has a high eccentricity (e = 0.65) and inclination (i = 39.3 deg) and 2021 is the only approach
within 0.1 au for at least another ~120 years. 2021 LD1 has a Tisserand parameter of 2.72, hinting
that its origin could be cometary.

2021 LD1 is circumpolar in the northern hemisphere until July 4th.
The object remains fainter than magnitude 18.5 during this encounter. 

We obtained a single target-of-opportunity radar track at Goldstone on July 11.

Pointing uncertainties with JPL/Horizons solution 16 are now small enough to
support the radar observations.  Thank you to everyone for your help 
with astrometry!


Orbital and Physical Characteristics  
Name                     2021 LD1                 
Asteroid number          not numbered                   
Discoverer               NEOWISE      
Discovery date           2021 Jun 02               
orbit type               Apollo                      
Close approach distance  0.065 au                  
Close approach date      2021 Jul 09               

semimajor axis           2.805 au                  
eccentricity             0.65                      
inclination              39.3 deg                  
Orbital period           4.70 years                
perihelion distance      0.988 au                  
aphelion distance        4.623 au                  
MOID                     0.028 au                  

absolute magnitude (H)   20.2                      
diameter                 ~750 m (J. Masiero for the NEOWISE team)
optical albedo           ~0.05  (J. Masiero for the NEOWISE team)   
rotation period          unknown                   
lightcurve amplitude     ~0.8 mag                   
pole direction           unknown                   
spectral class           unknown                   
PHA?                     Yes                        

Last update: 2021 July 12


Goldstone Radar Images of Asteroid 2021 LD1



Delay-Doppler radar images of 2021 LD1 obtained on July 11.
Resolution is 75 m x 0.95 Hz.  In each panel, range increases
down and Doppler frequency increases to the right, so the illumination comes from the
top and rotation is counterclockwise.  In the collage, time increases from the top left
to the right and then down,so the last frame in the sequence is at the lower
right.  If we assume that the two lobes are in contact, then the number of rows with 
echo power above the noise places a lower bound on the long axis of about 1200 meters.


Discovery M.P.E.C.


2021 LD1
https://www.minorplanetcenter.net/mpec/K21/K21L56.html



SNR Calculations

Goldstone SNRs

2021 LD1:  D = 0.75 km,  P = 2.0 h,  OC albedo = 0.1

DOY   start date      window       RA, dec   dist    runs      SNR/day SNR/run
185   2021 Jul  4  05:33-20:59      7, +60   0.0950   281         22      1
186   2021 Jul  5  06:29-21:02     15, +55   0.0851   295         33      2
187   2021 Jul  6  07:26-21:00     23, +49   0.0765   306         49      3
188   2021 Jul  7  08:20-20:55     30, +40   0.0699   310         67      4
189   2021 Jul  8  09:12-20:46     36, +30   0.0657   303         82      5
190   2021 Jul  9  10:02-20:33     42, +18   0.0646   281         85      5
191   2021 Jul 10  10:50-20:16     47,  +7   0.0665   246         72      5
192   2021 Jul 11  11:35-19:56     51,  -4   0.0713   203         50      4 Scheduled 1225-1355
193   2021 Jul 12  12:20-19:34     54, -13   0.0784   161         31      3
194   2021 Jul 13  13:03-19:09     57, -20   0.0872   122         17      2


Track Assignments


DOY    BOA   BOT   EOT   EOA
192    1055  1225  1355  1425  GSSR AST 2021 LD1


Goldstone tracks:
      UT                   UT          PST                 Duration Round-trip     
DOY   Date                 TX Window   TX Window           hh:mm    time (sec)   SNR/run
192   Jul 11    2021 LD1   1225-1355   0525-0655 Jul 11     1:30        70.5       4 


Uncertainties

2021 LD1
JPL/Horizons solution 16, # obs: 84 (70 days)
2021 July 8
 Date__(UT)__HR:MN     R.A._(a-appar)_DEC.            delta POS_3sigma  DOP_X_3sig  RT_delay_3sig
 2021-Jul-07 00:00 *m   25.90138  45.53966 0.07365758976517      1.264       73.35       0.006921
 2021-Jul-08 00:00 *m   32.56424  36.32353 0.06800736735267      1.679       48.14       0.006316
 2021-Jul-09 00:00 *m   38.44292  25.51801 0.06497752994466      2.281       19.51       0.005992
 2021-Jul-10 00:00 *m   43.57064  13.99081 0.06494127392159      2.898       24.16       0.005995
 2021-Jul-11 00:00 *m   48.01957   2.88136 0.06790499156995      3.330       52.96       0.006328 *
 2021-Jul-12 00:00 *m   51.87599  -6.92755 0.07350492017100      3.504       77.01       0.006949
 2021-Jul-13 00:00 *m   55.22548 -15.08690 0.08119286486020      3.475       94.58       0.007790
 2021-Jul-14 00:00 *m   58.14580 -21.66492 0.09043109525883      3.334      106.83       0.008788
 2021-Jul-15 00:00 *m   60.70434 -26.91208 0.10078572142616      3.149      115.27       0.009894

JPL/Horizons solution 12, # obs: 63 (62 days)
2021 June 30
 Date__(UT)__HR:MN     R.A._(a-appar)_DEC.            delta POS_3sigma  DOP_X_3sig  RT_delay_3sig
 2021-Jul-07 00:00 *m   25.90202  45.53868 0.07365880991676     14.665      117.64       0.010950
 2021-Jul-08 00:00 *m   32.56488  36.32217 0.06800859596175     19.558       82.37       0.010141
 2021-Jul-09 00:00 *m   38.44354  25.51629 0.06497898971377     24.250      127.23       0.010173
 2021-Jul-10 00:00 *m   43.57124  13.98886 0.06494317959648     27.347      199.53       0.011201
 2021-Jul-11 00:00 *m   48.02014   2.87936 0.06790749855946     28.035      253.76       0.013132 *
 2021-Jul-12 00:00 *m   51.87653  -6.92945 0.07350810688534     26.687      283.99       0.015664
 2021-Jul-13 00:00 *m   55.22599 -15.08862 0.08119675298267     24.284      298.05       0.018513
 2021-Jul-14 00:00 *m   58.14627 -21.66644 0.09043567869809     21.638      303.95       0.021503
 2021-Jul-15 00:00 *m   60.70479 -26.91341 0.10079098519271     19.175      306.27       0.024550

JPL/Horizons solution 8,  # obs: 47 (51 days)
 Date__(UT)__HR:MN     R.A._(a-appar)_DEC.            delta  POS_3sigma    DOP_X_3sig  RT_delay_3sig
 2021-Jul-07 00:00 *m   25.90219  45.53768 0.07366107354242     106.096        339.65       0.028496
 2021-Jul-08 00:00 *m   32.56501  36.32091 0.06801079337478     134.516        544.06       0.027944
 2021-Jul-09 00:00 *m   38.44365  25.51479 0.06498132442632     159.179        921.31       0.031992
 2021-Jul-10 00:00 *m   43.57132  13.98723 0.06494585161871     172.016       1235.13       0.041026
 2021-Jul-11 00:00 *m   48.02020   2.87773 0.06791066295801     169.668       1395.54       0.053488 *
 2021-Jul-12 00:00 *m   51.87657  -6.93096 0.07351185789560     155.990       1426.10       0.067382
 2021-Jul-13 00:00 *m   55.22601 -15.08998 0.08120113723633     137.564       1393.21       0.081431
 2021-Jul-14 00:00 *m   58.14629 -21.66764 0.09044071611390     119.170       1344.51       0.095118


Apparent Magnitudes, Solar Elongations, Lunar Elongations, and Lunar Illumination: 2021 LD1 JPL/Horizons solution 8 Date__(UT)__HR:MN R.A._(a-appar)_DEC. APmag delta S-O-T /r T-O-M/MN_Illu% 2021-Jun-21 00:00 *m 298.81143 68.06844 20.139 0.26459975697512 86.0359 /L 98.1/ 81.0472 2021-Jun-22 00:00 *m 300.81748 68.29770 20.059 0.25159518750646 85.6714 /L 98.9/ 89.4941 2021-Jun-23 00:00 * 303.08522 68.52125 19.976 0.23857328108483 85.2716 /L 99.1/ 95.7055 2021-Jun-24 00:00 * 305.66304 68.73257 19.888 0.22554587725443 84.8299 /L 98.6/ 99.2219 2021-Jun-25 00:00 * 308.60890 68.92167 19.797 0.21252714919778 84.3380 /L 97.4/ 99.8379 2021-Jun-26 00:00 * 311.99122 69.07339 19.701 0.19953430698047 83.7863 /L 95.3/ 97.6323 2021-Jun-27 00:00 * 315.88866 69.16496 19.601 0.18658858549852 83.1623 /L 92.5/ 92.9295 2021-Jun-28 00:00 * 320.38727 69.16238 19.496 0.17371664945885 82.4508 /L 89.0/ 86.2103 2021-Jun-29 00:00 * 325.57281 69.01536 19.387 0.16095261774056 81.6326 /L 84.8/ 78.0141 2021-Jun-30 00:00 * 331.51521 68.65055 19.273 0.14834102113312 80.6838 /L 80.2/ 68.8610 2021-Jul-01 00:00 * 338.24277 67.96304 19.156 0.13594118223825 79.5743 /L 75.0/ 59.2094 2021-Jul-02 00:00 * 345.70819 66.80707 19.037 0.12383376887275 78.2671 /L 69.4/ 49.4449 2021-Jul-03 00:00 * 353.75825 64.98773 18.919 0.11213062905558 76.7190 /L 63.4/ 39.8891 2021-Jul-04 00:00 * 2.12899 62.25653 18.806 0.10098936948225 74.8846 /L 57.1/ 30.8182 2021-Jul-05 00:00 * 10.48500 58.31513 18.706 0.09063401578064 72.7298 /L 50.8/ 22.4823 2021-Jul-06 00:00 * 18.49445 52.83765 18.629 0.08138092592606 70.2660 /L 45.3/ 15.1207 2021-Jul-07 00:00 *m 25.90219 45.53768 18.586 0.07366107354241 67.6178 /L 42.2/ 8.9705 2021-Jul-08 00:00 *m 32.56501 36.32091 18.582 0.06801079337477 65.1154 /L 43.7/ 4.2666 2021-Jul-09 00:00 *m 38.44365 25.51479 18.609 0.06498132442631 63.3097 /L 50.6/ 1.2332 2021-Jul-10 00:00 *m 43.57132 13.98723 18.645 0.06494585161870 62.7310 /L 61.7/ 0.0675 2021-Jul-11 00:00 *m 48.02020 2.87773 18.681 0.06791066295801 63.4785 /L 74.4/ 0.9182 2021-Jul-12 00:00 *m 51.87657 -6.93096 18.727 0.07351185789561 65.1510 /L 86.9/ 3.8632 2021-Jul-13 00:00 *m 55.22601 -15.08998 18.792 0.08120113723634 67.2066 /L 98.0/ 8.8891 2021-Jul-14 00:00 *m 58.14629 -21.66764 18.878 0.09044071611391 69.2632 /L 107.3/ 15.8780

Setups




CW setup:
---------------------------------------------------------------------------
TX polarization           RCP
RCV polarization          LCP & RCP
Frequency hops:           no hopping
Bandwidth:               5000 Hz 
TXoffset                 +500 Hz
FFT                      5000 for 1.0 Hz resolution 

Ranging setups:
---------------------------------------------------------------------------
10-usec
baud             10 usec
code            127
PRP            1270 usec
ncoh              1 
bandwidth       787 Hz   
FFT             128
resolution       6.15 Hz
TXoffset       +100 Hz  (echo in column 80)
---------------------------------------------------------------------------
11-usec 
baud             11 usec
code            127
PRP            1397 usec
ncoh              1 
bandwidth       716 Hz   
FFT             128
resolution      5.6 Hz
TXoffset     +100 Hz  (echo in column 82) 
-------------------------------------------------------------------------
1-usec 
baud              1 usec
code            255
ncoh              8
bandwidth       245 Hz   
FFT             128
resolution        3.8 Hz
TXoffset        +50 Hz  (echo in column 116)
---------------------------------------------------------------------

Instructions

NOTE: Data should be moved to the appropriate subdirectories in aardvark:/export/data0/2021ld1/raw/

POINTING:

  OSOD and predicts are on aardvark:



POINTING  

...Not yet available...

Transmit offsets are given in millidegrees.  


PRDX.OUT.14f-14-14.s?? TRANSMITTER: STATION #14, RECEIVER: STATION #14 RECEIVER U.T. RANGE DOPPLER LHA DEC RA EL

2021 LD1 GOLDSTONE MASTERLOG

============================================================================== ----------------------------------------------------- ...Not yet available... -----------------------------------------------------
Dr. Lance A. M. Benner | PHONE: (818) 354-7412 Mail Stop 183-601 | FAX: (818) 393-4445 Jet Propulsion Laboratory | email: lance.benner@jpl.nasa.gov California Institute of Technology | Plan: To live long and prosper Pasadena, CA 91109-8099 https://echo.jpl.nasa.gov/asteroids/2021LD1/2021LD1.goldstone.planning.html

Asteroid Radar Astronomy
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