KPL/PCK

Asteroid Bennu P_constants (PcK) SPICE kernel file
=======================================================================
 
   This text PCK contains rotational and ellipsoidal shape constants
   for asteroid Bennu.
 
 
Version and Date
--------------------------------------------------------
   Version 1.6 -- September 14, 2020 -- Michael Nolan, LPL/UA
                                        Jason Leonard, KinetX

      Updated rotational constants based on FDS / nav pole solution
      in [9] and shape model v042 [8].

   Version 1.5 -- September 16, 2019 -- Michael Nolan, LPL/UA
                                        Jason Leonard, KinetX

      Updated rotational and ellipsoid constants based on FDS / nav
      pole solution in [7] and shape model v042 [8].

   Version 1.4 -- February 15, 2019 -- Michael Nolan, LPL/UofA

      Updated rotational constants based on FDS pole solution in
      [6] along with the acceleration determined in [5]. It matches
      the solution in [6] at 2019 Jan 01 12:00:00 TDB to within
      0.0001 degrees

   Version 1.3 -- February 3, 2019  -- Michael Nolan, LPL/UofA

      Updated rotational constants based on shape modelling in [4]
      along with the acceleration determined in [5]. It matches
      the solution in [4] at 2019 Jan 01 12:00:00 TDB

   Version 1.2 -- January 11, 2019  -- Michael Nolan, LPL/UofA
                                       Boris Semenov, NAIFJPL

      Updated prime meridian location (W0) and rotation terms (W1, W2)
      based on [2], [3], and Bennu lightcurve observations in flight.

      Updated ellipsoid parameters based on shape modelling in [3].

   Version 1.1 -- October 22, 2018  -- Michael Nolan, LPL/UofA
                                       Boris Semenov, NAIF/JPL

      Updated prime meridian location (W0) and rotation terms (W1, W2)
      based on [2] and Bennu lightcurve observations in flight.

   Version 1.0 -- November 4, 2014  -- Boris Semenov, NAIF/JPL
   
      Initial version released for official use by OSIRIS-Rex project,
      containing values for the pole direction, rotation period and
      shape from [1].

 
Disclaimer
--------------------------------------------------------
 
   This constants file may not contain the parameter values that you
   prefer. Note that this file may be readily modified by you or anyone
   else. NAIF suggests that you inspect this file visually before
   proceeding with any critical or extended data processing.
 
   NAIF requests that you update the ``by line'' and date if you modify
   the file.
 
 
Sources
--------------------------------------------------------
 
   The sources for the constants listed in this version of this file
   are:
 
     1) (101955) Bennu Design Reference Asteroid, 
        Document Number: OREX-XLSX-04.00-00001, Rev_10,
        Version: 2014 October 10
        (OREX-XLSX-04.00-00001_Rev_10_Bennu_DRA_Final.xlsx)

     2) M.C. Nolan et al. (2018). Detection of YORP on
        Bennu using HST Lightcurve Observations. Submitted
        to Geophysical Research Letters.

     3) O.S. Barnouin et al. (2019) Exploring the Shape of
        (101955) Bennu with OSIRIS-REx. Submitted to Nature.

     4) Product report for OSIRIS-REx shape model v020

     5) C.W. Hergenrother at al. (2019). Photometric Properties,
        Rotation State, and Operational Environment of Asteroid
        (101955) Bennu from OSIRIS-REx Observations.  Submitted to
        Nature Communications.

     6) 190215_Pole_Final in the OSIRIS-REx FDS to ALTWG/JPL/SPOC
        POLE PRODUCT FILE RELEASE FORM

     7) bennu_pck_fds_v42_final.tpc in the OSIRIS-REx INTERNAL FDS
        to ALTWG ITERATION PRODUCT FILE RELEASE FORM FOR V42

     8) Product report for OSIRIS-REx shape mode v042

     9) bennu_pck_fds_v42_final_v3.tpc in the OSIRIS-REx FDS
        FILE RELEASE FORM FOR UPDATED V42 PCK (V3)


Orientation constants for asteroid Bennu
--------------------------------------------------------
 
   The inertial reference frame for the Bennu rotation constants is
   J2000; this is the default reference frame for PCK orientation data.
 
   The epoch of the Bennu rotation constants is J2000; this is Julian
   ephemeris date (JED) 2451545.0.
 
   The NAIF integer code for Bennu is 2101955. See the NAIF_IDs
   required reading for further information on NAIF integer codes.
 
   The LONG_AXIS keyword providing the offset between the longest axis
   of the triaxial ellipsoid used to model Bennu and the Bennu prime
   meridian is not used by SPICE geometry software. It is considered 
   deprecated and provided solely for backwards compatibility.


Values in the Version 1.0

   The pole direction, prime meridian location, and rotation period in
   this version are set to the following values from [1]:

    "
     3.1.1  Rotation Period               4.297461              hours

     3.1.6  Pole Position (J200 RA/DEC)   (+86.6388, -65.1086)  deg

     3.1.7  Location of Prime Meridian    89.6456               deg
            (epoch J2000)
    "

   The rotation rate (W1) below was derived from the period and is
   provided in degrees/day.

   The corresponding keywords were set as follows (saved in comments
   for trace-ability, lower-cased to prevent accidental use):

         body2101955_pole_ra    = (  86.6388       0.              0. )
         body2101955_pole_dec   = ( -65.1086       0.              0. )
         body2101955_pm         = (  89.6456    2010.4894494679531 0. )
         body2101955_long_axis  = (   0.                              )


Values in the Version 1.1

   The pole direction in this version is the same as in the version 1.0,
   based on [1].

   The prime meridian location (W0) and rotation terms (W1 and W2) in
   this version are from [2], computed from fitting lightcurves, and
   adjusting W0 until the phase at 2005 Sep 14 (epoch of Radar model)
   matches the version 1.0 based on the phase difference between
   rq36.v.mod1002-submitted and rq36.p5.pdot30.mod models.

   The corresponding keywords were set as follows (saved in comments
   for traceability, lower-cased to prevent accidental use):

         body2101955_pole_ra    = (  86.6388       0.              0. )
         body2101955_pole_dec   = ( -65.1086       0.              0. )
         body2101955_pm         = ( 154.9182 2011.14576050637 1.5e-06 )
         body2101955_long_axis  = (   0.                              )


Values in the Version 1.2

   The pole direction in this version is from [3], based on the Nav
   solution from 2019 Jan 09.

   The rotation terms (W1 and W2) use the method of [2] but include
   data through approach. The prime meridian location (W0) was
   determined by fixing W1 and W2 and then adjusting W0 in ISIS until
   rendered Approach images visually showed the chosen Prime Meridian
   feature from [3] at 0 longitude.

   The corresponding keywords were set as follows (saved in comments
   for traceability, lower-cased to prevent accidental use):

         body2101955_pole_ra    = (  85.3400       0.              0. )
         body2101955_pole_dec   = ( -60.1600       0.              0. )
         body2101955_pm         = ( 146.8404 2011.146953279 1.5e-06   )
         body2101955_long_axis  = (   0.                              )

Values in Version 1.3

   The rotation terms and pole directon in this version are from [4],
   based on the Nav solution from 2019 Jan 16, OD90. These rotation
   coefficients were used in creating shape model v020. The rotation
   terms use the acceleration from [5] along with the rotation phase 
   and rate from [4] recast to give the same rate and phase as [4] at
   2019 Jan 01 12:00:00 TDB ("J2019").

   [4] has rotation constants of ( 45.6089 2011.17201568 0 ). J2019 is
   6940 days later than J2000. The T^2 term W2 from [5] is 0.000001815.
   W1 = 2011.17201568 - (2 * W2 * 6940) = 2011.14682348
   W0 = 45.6089 + (2011.17201568 - 2011.14682348) * 6940
      - 0.000001815 * 6940 * 6940 = 133.0258

   The corresponding keywords were set as follows (saved in comments
   for traceability, lower-cased to prevent accidental use):
         body2101955_pole_ra    = (  85.6474       0.              0. )
         body2101955_pole_dec   = ( -60.1697       0.              0. )
         body2101955_pm         = ( 133.0258  2011.14682348 1.815e-06 )
         body2101955_long_axis  = (   0.                              )
 
Values in Version 1.4

   The rotation terms and pole directon in this version are from [6],
   Delivered from FDS to SPOC on 2019 Feb 15.
   The rotation terms use the acceleration from [5] along with the
   rotation phase and rate from [6] recast to give the same rate
   and phase as [6] at 2019 Jan 01 12:00:00 TDB ("J2019").

   [6] has rotation constants of:
   Pole_RA                       : 8.545674147094455E+01 deg
   Pole_Dec                      :-6.035739923373426E+01 deg
   PM                            : 4.839868214726448E+01 deg (j2000)
   Rotation_Rate                 : 2.011171643153616E+03 deg/day

   J2019 is 6940 days later than J2000. The T^2 term W2 from [5]
   is 0.000001815. W2 is half the acceleration rate.

   W1 = 2011.17164315 - (2 * .000001815 * 6940) = 2011.14645095
   W0 = 48.3987 + (2011.17164315 - 2011.14645095) * 6940 
      - 0.000001815 * 6940 * 6940 = 135.8156

   The corresponding keywords were set as follows (saved in
   comments for traceability, lower-cased to prevent accidental use):

         body2101955_pole_ra    = (  85.4567       0.              0. )
         body2101955_pole_dec   = ( -60.3574       0.              0. )
         body2101955_pm         = ( 135.8156  2011.14645095 1.815e-06 )
         body2101955_long_axis  = (   0.                              )

Values in Previous Version 1.5

   The rotation terms and pole directon in this version are from [7],
   Delivered from FDS to SPOC on 2019 Sep 15.
   The rotation terms include the acceleration from [5] as part of
   the solution in [7], however it was not fit and no uncertainty was
   calculated. The additional corrections used in Version 1.4 were
   therefore not needed or applied.

   From [7], the uncertainties in the rotational constants are:
   "
   SIG_Pole_RA                   : 0.00034 deg
   SIG_Pole_Dec                  : 0.00010 deg
   SIG_PM                        : 0.00034 deg
   SIG_Rotation_Rate             : 2.778e-11 deg/sec
   "
   The rotation sigma converted to deg/day is 2.778E-11 * 86400
   = 0.000002400 deg/day
   Those are all formal fit uncertainties. Estimated actual
   uncertainties are:
   SIG_RA   = 0.005 deg
   SIG_Dec  = 0.010 deg
   SIG_Spin = 1.0e-08 deg/s (0.00086 deg/day)
   SIG_PM   = 0.1 deg (~50 cm)

   The corresponding keywords were set as follows (saved in comments
   for traceability, lower-cased to prevent accidental use):

         body2101955_pole_ra    = (  85.45218      0.              0. )
         body2101955_pole_dec   = ( -60.36780      0.              0. )
         body2101955_pm       = ( 139.13621 2011.1459760340 1.815e-06 )
         body2101955_long_axis  = (   0.                              )

Values in Current Version 1.6

   The rotation terms and pole directon in this version are from [9],
   Delivered from FDS to SPOC via the orx FOB on 2020 Sep 4.
   The rotation terms include the acceleration from [5] as part of
   the solution in [9], however it was not fit and no uncertainty was
   calculated. The additional corrections used in Version 1.4 were
   therefore not needed or applied.

   From [9], the formal fit uncertainties in the rotational constants
   are:

   SIG_Pole_RA                   : 0.0013 deg
   SIG_Pole_Dec                  : 0.00058 deg
   SIG_PM                        : 0.0012 deg
   SIG_Rotation_Rate             : 2.5e-06 deg/day


   Estimated actual uncertainties are:
   SIG_Pole_RA                   : 0.005 deg (same as v15)
   SIG_Pole_Dec                  : 0.010 deg (same as v15)
   SIG_PM(j2000)                 : 0.025 deg
   SIG_Rotation_Rate             : 2.5e-06 deg/day

   The rotational acceleration is from [5] and was not fit; no
   uncertainty was estimated.

   These updated pck Bennu orientation parameters are based on combined
   OD filter of Detailed Survey, Recon B, CP/R and MP/R. This OD
   solution assumed the V42 shape model with landmarks scaled at
   0.99896 and radio/landmark tracking spans as follows:
   Detailed Survey March 5-30, 2019, April 2-20, 2019
   Recon-B Jan 14-23, 2020
   CP Rehearsal Apr 1-18, 2020
   MP Rehearsal July 9-August 11, 2020


      \begindata
 
         BODY2101955_POLE_RA    = (  85.46097      0.              0. )
         BODY2101955_POLE_DEC   = ( -60.35860      0.              0. )
         BODY2101955_PM     = ( 140.68835 2011.145755336826 1.815E-06 )
         BODY2101955_LONG_AXIS  = (   0.                              )

      \begintext

Radii for asteroid Bennu
--------------------------------------------------------

Values in Versions 1.0 and 1.1

  The radii in this version are set based on following values from [1]:

       "
        2.1.2  Polar Dimension               508               meters

        2.1.3  Equatorial Dimensions         565 x 535         meters
       "

   The radii below are 1/2s of the polar and equatorial dimensions
   provided in kilometers.  The corresponding keywords were set as
   follows (saved in comments for trace-ability, lower-cased to
   prevent accidental use):


         body2101955_radii   = (   0.2825       0.2675       0.254 )
 
Values in Version 1.2 and Version 1.3

  The radii in this version are set based on following values from [3]:

       "The extent of the GDTM is (563.87 +/- 0.17) x (536.09 +/- 0.17)
        x (498.42 +/- 0.17) m."

   The radii below are 1/2s of the polar and equatorial dimensions
   provided in kilometers.
   The corresponding keywords were set as
   follows (saved in comments for trace-ability, lower-cased to
   prevent accidental use):

         body2101955_radii   = (   0.281935    0.268045       0.24921 )

Values in Version 1.4

   From [4]:
   "Extent (km):
   X: [-0.27915000915527344, 0.28558000922203064]
   Y: [-0.263949990272522, 0.2721500098705292]
   Z: [-0.2445800006389618, 0.25391000509262085]
   "
   The radii below are the mean of the + and - extents, ignoring the
   floating point rounding errors.
   The corresponding keywords were set as
   follows (saved in comments for trace-ability, lower-cased to
   prevent accidental use):

         body2101955_radii   = (   0.282365    0.268050      0.249245 )

Values in the Version 1.5 and Current Version 1.6

   From [8]:
   "Extent (km): 
  X: [-0.27955999970436096, 0.2865700125694275]
  Y: [-0.2648099958896637, 0.27761998772621155]
  Z: [-0.2448599934577942, 0.25457999110221863]
  "
   The radii below are the mean of the + and - extents, ignoring the
   floating point rounding errors.

      \begindata

         BODY2101955_RADII   = (   0.283065    0.271215      0.249720 )

      \begintext
 

End of PCK file.
