Brief Guide to Doing SPICE Hands-On Lessons Using WGC

Table of Contents

   Brief Guide to Doing SPICE Hands-On Lessons Using WGC
      Overview
      WGC and WGC Tutorial URLs
      Doing ``Remote Sensing'' Hands-On Lesson Using WGC
         Kernels Used
         Time Conversion (convtm)
         Obtaining Target States and Positions (getsta)
         Spacecraft Orientation and Reference Frames (xform)
         Computing Sub-spacecraft and Sub-solar Points (subpts)
         Intersecting Vectors with a Triaxial Ellipsoid (fovint)
      Doing ``In-situ Sensing'' Hands-On Lesson Using WGC
         Kernels Used
         Step-1: ``UTC to ET''
         Step-2: ``SCLK to ET''
         Step-3: ``Spacecraft State''
         Step-4: ``Sun Direction''
         Step-5: ``Sub-Spacecraft Point''
         Step-6: ``Spacecraft Velocity''
      Doing ``Geometric Event Finding'' Hands-On Lesson Using WGC
         Kernels Used
         Find View Periods
         Find Times when Target is Visible
      Doing ``Binary PCK'' Hands-On Lesson Using WGC
         Moon rotation (mrotat)
         Earth rotation (erotat)




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Brief Guide to Doing SPICE Hands-On Lessons Using WGC





October 20, 2014



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Overview




This guide provides brief instructions on how to do SPICE ``Remote Sensing'', ``In-situ Sensing'', ``Geometric Event Finding'', and ``Binary PCK'' hands-on lessons using the SPICE WebGeocalc (WGC) tool.

Instructions for each lesson are provided in a separate section below. They follow the lesson steps and individual assignments within each step, indicate which WGC computation panels (``calculations'') should be used and what inputs should be entered or selected in these calculations, and what key outputs should be expected from WGC. Where applicable, they indicate that a particular quantity computed in the lesson cannot be computed by WGC.



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WGC and WGC Tutorial URLs




WGC can be accessed at:

   http://wgc.jpl.nasa.gov:8080/webgeocalc/#NewCalculation
The WGC tutorial is provided at:

   http://naif.jpl.nasa.gov/pub/naif/toolkit_docs/Tutorials/pdf/individual_docs/47_webgeocalc.pdf


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Doing ``Remote Sensing'' Hands-On Lesson Using WGC






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Kernels Used



Use the ``SPICE Class - Remote Sensing Lesson Kernels'' kernel set appearing near the bottom of the ``Kernel selection:'' menu to do all steps in this lesson.



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Time Conversion (convtm)



To compute ET seconds past J2000, specify/select the following inputs in the ``Time Conversion'' calculation:

   Time system               UTC
   Time format               Calendar date and time
   Input time                2004 jun 11 19:32:00
   Output time system        TDB
   Output time format        Seconds past J2000
WGC will return the following ET seconds past J2000:

   140254384.184620
To compute calendar ET in the default format, specify/select the following inputs in the ``Time Conversion'' calculation:

   Time system               UTC
   Time format               Calendar date and time
   Input time                2004 jun 11 19:32:00
   Output time system        TDB
WGC will return the following calendar ET time string:

   2004-06-11 19:33:04.184625 TDB
To compute calendar ET in a custom format, specify/select the following inputs in the ``Time Conversion'' calculation:

   Time system               UTC
   Time format               Calendar date and time
   Input time                2004 jun 11 19:32:00
   Output time system        TDB
   Custom format             YYYY-MON-DDTHR:MN:SC ::TDB
WGC will return the following calendar ET time string:

   2004-JUN-11T19:33:04
To compute spacecraft clock time, specify/select the following inputs in the ``Time Conversion'' calculation:

   Time system               UTC
   Time format               Calendar date and time
   Input time                2004 jun 11 19:32:00
   Output time system        Spacecraft clock (SCLK=-82)
WGC will return the following SCLK time string:

   1/1465674964.105


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Obtaining Target States and Positions (getsta)



To compute the apparent state of Phoebe as seen from CASSINI in the J2000 frame, specify/select the following inputs in the ``State Vector'' calculation:

   Target                    PHOEBE
   Observer                  CASSINI
   Reference frame           J2000
   Light propagation         To observer
   Light-time algorithm      Newtonian
   Stellar aberration        Corrected for stellar aberration
   Time system               UTC
   Time format               Calendar date and time
   Input time                2004 JUN 11 19:32:00
   State representation      Rectangular
WGC will return the following state vector, km and km/s:

   -119.92092897
   2194.13933986
   -57.63897986
   -5.98023114
   -2.11880531
   -0.29482213
To compute the apparent position of Earth as seen from CASSINI in the J2000 frame and one way light time between CASSINI and the apparent position of Earth, specify/select the following inputs in the ``State Vector'' calculation:

   Target                    EARTH
   Observer                  CASSINI
   Reference frame           J2000
   Light propagation         To observer
   Light-time algorithm      Newtonian
   Stellar aberration        Corrected for stellar aberration
   Time system               UTC
   Time format               Calendar date and time
   Input time                2004 JUN 11 19:32:00
   State representation      Rectangular
WGC will return the following position vector, km, and one way light time, s:

   353019393.12261910
   -1328180352.14030500
   -568134171.69730540
   4960.42691203
To compute the apparent position of Sun as seen from Phoebe in the J2000 frame, specify/select the following inputs in the ``State Vector'' calculation:

   Target                    SUN
   Observer                  PHOEBE
   Reference frame           J2000
   Light propagation         To observer
   Light-time algorithm      Newtonian
   Stellar aberration        Corrected for stellar aberration
   Time system               UTC
   Time format               Calendar date and time
   Input time                2004 JUN 11 19:32:00
   State representation      Rectangular
WGC will return the following position vector, km:

   376551465.27159620
   -1190495630.30282120
   -508438699.11000470
Note that WGC will also compute the distance between Sun and Phoebe body centers, km:

   1348176829.09957000
but it cannot convert this distance to AUs.



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Spacecraft Orientation and Reference Frames (xform)



To compute the apparent state of Phoebe as seen from CASSINI in the IAU_PHOEBE body-fixed frame, specify/select the following inputs in the ``State Vector'' calculation:

   Target                    PHOEBE
   Observer                  CASSINI
   Reference frame           IAU_PHOEBE
   Light propagation         To observer
   Light-time algorithm      Newtonian
   Stellar aberration        Corrected for stellar aberration
   Time system               UTC
   Time format               Calendar date and time
   Input time                2004 JUN 11 19:32:00
   State representation      Rectangular
WGC will return the following state vector, km and km/s:

   -1982.63976162
   -934.53047112
   -166.56259513
   3.97083213
   -3.81249566
   -2.37166299
WGC does not have a separate calculation to compute angles between directions to objects and instrument boresights or axes of a reference frame, making such computations not possible in general. But for cases when the axis is ``Z'' such computations can be done using the ``State Vector'' calculation with the ``Spherical Coordinates'' output, in which the colatitude is equal to the desired angle.

To compute the angular separation between the apparent position of Earth and the CASSINI high gain antenna boresight, specify/select the following inputs in the ``State Vector'' calculation:

   Target                    EARTH
   Observer                  CASSINI
   Reference frame           CASSINI_HGA
   Light propagation         To observer
   Light-time algorithm      Newtonian
   Stellar aberration        Corrected for stellar aberration
   Time system               UTC
   Time format               Calendar date and time
   Input time                2004 JUN 11 19:32:00
   State representation      Spherical
WGC will return the following output colatitude, deg:

   71.92414848


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Computing Sub-spacecraft and Sub-solar Points (subpts)



To compute the apparent sub-observer point of CASSINI on Phoebe in the IAU_PHOEBE frame, specify/select the following inputs in the ``Sub-Observer Point'' calculation:

   Target                    PHOEBE
   Reference frame           IAU_PHOEBE
   Observer                  CASSINI
   Sub-point type            Near point on ellipsoid
   Light propagation         To observer
   Light-time algorithm      Newtonian
   Stellar aberration        Corrected for stellar aberration
   Time system               UTC
   Time format               Calendar date and time
   Input time                2004 JUN 11 19:32:00
   Position representation   Rectangular
WGC will return the following position vector, km:

   104.49789074
   45.26884577
   7.38331473
Note that WCG will compute the altitude but it will be labeled ``Observer Distance (km)'' in the output table and will have the following distance, km:

   2084.11604205
To compute the apparent sub-solar point on Phoebe as seen from CASSINI in the IAU_PHOEBE frame , specify/select the following inputs in the ``Sub-Solar Point'' calculation:

   Calculation type          Sub-Solar Point
   Target                    PHOEBE
   Reference frame           IAU_PHOEBE
   Observer                  CASSINI
   Sub-point type            Near point on ellipsoid
   Light propagation         To observer
   Light-time algorithm      Newtonian
   Stellar aberration        Corrected for stellar aberration
   Time system               UTC
   Time format               Calendar date and time
   Input time                2004 JUN 11 19:32:00
   Position representation   Rectangular
WGC will return the following position vector, km:

   78.68071625
   76.87865160
   -21.88456729


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Intersecting Vectors with a Triaxial Ellipsoid (fovint)



To compute the Cartesian position vectors of the FOV boundary vector surface intercept points in the IAU_PHOEBE frame, specify/select the following inputs in the ``Surface Intercept Point'' calculation:

   Target                    PHOEBE
   Reference frame           IAU_PHOEBE
   Observer                  CASSINI
   Ray vector                CASSINI_ISS_NAC
                             field-of-view boundary vectors
   Light propagation         To observer
   Light-time algorithm      Newtonian
   Stellar aberration        Corrected for stellar aberration
   Time system               UTC
   Time format               Calendar date and time
   Input time                2004 JUN 11 19:32:00
   Position representation   Rectangular
WGC will return the following position vectors, km:

   91.02635667
   67.19017758
   2.03016242
 
   91.02635667
   67.19017758
   2.03016242
 
   91.02635667
   67.19017758
   2.03016242
 
   91.02635667
   67.19017758
   2.03016242
To compute the planetocentric longitudes and latitudes of the FOV boundary vector surface intercept points in the IAU_PHOEBE frame, specify/select the following inputs in the ``Surface Intercept Point'' calculation:

   Target                    PHOEBE
   Reference frame           IAU_PHOEBE
   Observer                  CASSINI
   Ray vector                CASSINI_ISS_NAC
                             field-of-view boundary vectors
   Light propagation         To observer
   Light-time algorithm      Newtonian
   Stellar aberration        Corrected for stellar aberration
   Time system               UTC
   Time format               Calendar date and time
   Input time                2004 JUN 11 19:32:00
   Position representation   Planetocentric
WGC will return the following longitudes and latitudes, deg:

   36.43251123
   1.02800787
 
   36.55583078
   7.49186596
 
   43.42988023
   7.37325329
 
   43.23917363
   0.86454948
Both computations above also returned the illumination angles the FOV boundary vector surface intercept points but these angles were omitted from the output shown above.

To compute the Cartesian position vectors of the FOV boresight surface intercept point in the IAU_PHOEBE frame, specify/select the following inputs in the ``Surface Intercept Point'' calculation:

   Target                    PHOEBE
   Reference frame           IAU_PHOEBE
   Observer                  CASSINI
   Ray vector                CASSINI_ISS_NAC boresight
   Light propagation         To observer
   Light-time algorithm      Newtonian
   Stellar aberration        Corrected for stellar aberration
   Time system               UTC
   Time format               Calendar date and time
   Input time                2004 JUN 11 19:32:00
   Position representation   Rectangular
WGC will return the following position vector, km:

   86.39001297
   72.08919557
   8.25459687
To compute the planetocentric longitude and latitude of the FOV boresight surface intercept point in the IAU_PHOEBE frame and the illumination angles at this point, specify/select the following inputs in the ``Surface Intercept Point'' calculation:

   Target                    PHOEBE
   Reference frame           IAU_PHOEBE
   Observer                  CASSINI
   Ray vector                CASSINI_ISS_NAC boresight
   Light propagation         To observer
   Light-time algorithm      Newtonian
   Stellar aberration        Corrected for stellar aberration
   Time system               UTC
   Time format               Calendar date and time
   Input time                2004 JUN 11 19:32:00
   Position representation   Planetocentric
WGC will return the following longitude and latitude, deg:

   39.84371945
   4.19587780
and the following incidence, emission, and phase angles, deg:

   18.24722120
   17.85830930
   28.13948173
WGC cannot compute the local solar time at the boresight intercept point.



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Doing ``In-situ Sensing'' Hands-On Lesson Using WGC






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Kernels Used



Use the ``SPICE Class - In-situ Sensing Lesson Kernels'' kernel set appearing near the bottom of the ``Kernel selection:'' menu to do all steps in this lesson.



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Step-1: ``UTC to ET''



To compute ET seconds past J2000 for a given UTC string, specify/select the following inputs in the ``Time Conversion'' calculation:

   Time system               UTC
   Time format               Calendar date and time
   Input time                2004-06-11T19:32:00
   Output time system        TDB
   Output time format        Seconds past J2000
WGC will return the following ET seconds past J2000:

   140254384.184620


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Step-2: ``SCLK to ET''



To compute ET seconds past J2000 for a given SCLK string, specify/select the following inputs in the ``Time Conversion'' calculation:

   Time system               Spacecraft clock (SCLK=-82)
   Time format               Spacecraft clock string
   Input time                1465674964.105
   Output time system        TDB
   Output time format        Seconds past J2000
WGC will return the following ET seconds past J2000:

   140254384.183430
Either the input SCLK time or these output ET seconds past J2000 should be used as the input time in all remaining ``In-situ Sensing'' lesson steps in order for WGC to compute values matching the results provided in the programming lesson. The output ET seconds may be saved for future use in the WGC ``Saved Values'' area by simply clicking on them with the left mouse button. The saved value can then be drag-n-dropped from the ``Saved Values'' area into the empty ``Time:'' box in the next calculation.



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Step-3: ``Spacecraft State''



To compute the geometric state of the CASSINI spacecraft with respect to the Sun in the Ecliptic frame, specify/select the following inputs in the ``State Vector'' calculation:

   Target                    CASSINI
   Observer                  SUN
   Reference frame           ECLIPJ2000
   Light propagation         No correction
   Time system               TDB
   Time format               Seconds past J2000
   Input time                140254384.183430
   State representation      Rectangular
WGC will return the following state vector, km and km/s:

   -376599061.91656125
   1294487780.92915730
   -7064853.05469811
   -5.16422619
   0.80171891
   0.04060306


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Step-4: ``Sun Direction''



To compute the apparent direction of the Sun in the INMS frame, specify/select the following inputs in the ``State Vector'' calculation:

   Target                    SUN
   Observer                  CASSINI
   Reference frame           CASSINI_INMS
   Light propagation         To observer
   Light-time algorithm      Newtonian
   Stellar aberration        Corrected for stellar aberration
   Time system               TDB
   Time format               Seconds past J2000
   Input time                140254384.183430
   State representation      Rectangular
WGC will return the following position vector, km:

   -391245772.45811266
   1188593024.20844320
   501745827.05297270


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Step-5: ``Sub-Spacecraft Point''



To compute the planetocentric longitude and and latitude of the CASSINI sub-spacecraft point on Phoebe, specify/select the following inputs in the ``Sub-Observer Point'' calculation:

   Target                    PHOEBE
   Reference frame           IAU_PHOEBE
   Observer                  CASSINI
   Sub-point type            Near point on ellipsoid
   Light propagation         No correction
   Time system               TDB
   Time format               Seconds past J2000
   Input time                140254384.183430
   Position representation   Planetocentric
WGC will return the following longitude and latitude, deg:

   23.42315899
   3.70979740
WGC cannot compute the direction from the CASSINI spacecraft to the sub-spacecraft point in the INMS frame.



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Step-6: ``Spacecraft Velocity''



WGC cannot calculate the CASSINI spacecraft velocity with respect to Phoebe in the INMS frame as described in this step of the programming lesson.



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Doing ``Geometric Event Finding'' Hands-On Lesson Using WGC






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Kernels Used



Use the ``SPICE Class - Geometric Event Finding Lesson Kernels'' kernel set appearing near the bottom of the ``Kernel selection:'' menu to do all steps in this lesson.



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Find View Periods



To find the set of time intervals when the Mars Express (MEX) is visible from the DSN station DSS-14, specify/select the following inputs in the ``Position Event Finder'' calculation:

   Target                      MEX
   Observer                    DSS-14
   Reference frame             DSS-14_TOPO
   Light propagation           To observer
   Light-time algorithm        Converged Newtonian
   Stellar aberration          Corrected for stellar aberration
   Time system                 TDB
   Time format                 Calendar date and time
   Time range                  2004 MAY 2 to 2004 MAY 6,
                               step 300 seconds
   Coordinate condition        Latitude is greater than 6
   Output time unit            hours
   Complement result window    no
   Result interval adjustment  No adjustment
   Result interval filtering   No filtering
WGC will return the following interval start and stop times:

   2004-05-02 00:00:00.000000 TDB
   2004-05-02 05:35:03.096376 TDB
 
   2004-05-02 16:09:14.078641 TDB
   2004-05-03 05:33:57.257816 TDB
 
   2004-05-03 16:08:02.279561 TDB
   2004-05-04 05:32:50.765340 TDB
 
   2004-05-04 16:06:51.259358 TDB
   2004-05-05 05:31:43.600189 TDB
 
   2004-05-05 16:05:40.994061 TDB
   2004-05-06 00:00:00.000000 TDB
Make sure to save these output intervals in the WGC ``Saved Values'' area using the ``Save All Intervals'' button to make them available for use as input to the next step of the lesson.



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Find Times when Target is Visible



To find the set of time intervals when the Mars Express Orbiter (MEX) spacecraft is visible from the DSN station DSS-14 and and is not occulted by Mars, specify/select the following inputs in the ``Occultation Event Finder'' calculation:

   Calculation type            Occultation Event Finder
   Occultation type            Any
   Front body                  MARS
   Front body shape            Ellipsoid
   Front body frame            IAU_MARS
   Back body                   MEX
   Back body shape             Point
   Back body frame
   Observer                    DSS-14
   Light propagation           To observer
   Light-time algorithm        Converged Newtonian
   Time system                 TDB
   Time format                 Calendar date and time
   Output time unit            hours
   Complement result window    yes
   Result interval adjustment  No adjustment
   Result interval filtering   No filtering
To use the time intervals found by the previous step as the input to this calculation, select ``List of Intervals'' in the ``Input times:'' selector and drag and drop saved intervals from the ``Saved Values'' area into the empty ``List of intervals:'' box.

WGC will return the following interval start and stop times:

   2004-05-02 00:00:00.000000 TDB
   2004-05-02 04:49:30.827635 TDB
 
   2004-05-02 05:35:03.096376 TDB
   2004-05-02 05:35:03.096376 TDB
 
   2004-05-02 16:09:14.078641 TDB
   2004-05-02 20:00:22.514122 TDB
 
   2004-05-02 21:01:38.222068 TDB
   2004-05-03 03:35:42.256777 TDB
 
   2004-05-03 04:36:42.484694 TDB
   2004-05-03 05:33:57.257816 TDB
 
   2004-05-03 16:08:02.279561 TDB
   2004-05-03 18:46:26.013964 TDB
 
   2004-05-03 19:46:54.618795 TDB
   2004-05-04 02:21:44.562990 TDB
 
   2004-05-04 03:21:56.347988 TDB
   2004-05-04 05:32:50.765340 TDB
 
   2004-05-04 16:06:51.259358 TDB
   2004-05-04 17:32:25.809031 TDB
 
   2004-05-04 18:32:05.975318 TDB
   2004-05-05 01:07:48.264966 TDB
 
   2004-05-05 02:07:11.601765 TDB
   2004-05-05 05:31:43.600189 TDB
 
   2004-05-05 16:05:40.994061 TDB
   2004-05-05 16:18:35.560693 TDB
 
   2004-05-05 17:17:27.717224 TDB
   2004-05-05 23:54:04.672052 TDB
Note that the returned list contains 13 intervals instead of 12 shown in the output of this step in the programming lesson. This is due to a bug in the current version of WGC, which in some cases returns bogus zero-length intervals in addition to the actual intervals when the output window complement is requested. In this case the second interval in the output is a bogus singleton interval that should not be there. WGC's output window filtering option can be used as a workaround to remove such intervals before the WGC window complement algorithm is fixed.



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Doing ``Binary PCK'' Hands-On Lesson Using WGC






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Moon rotation (mrotat)



Use the ``SPICE Class - Binary PCK Lesson Kernels (Moon)'' kernel set appearing near the bottom of the ``Kernel selection:'' menu to do this step in this lesson.

To compute the Moon-Earth direction using the low accuracy PCK and the IAU_MOON frame, specify/select the following inputs in the ``State Vector'' calculation:

   Target                    EARTH
   Observer                  MOON
   Reference frame           IAU_MOON
   Light propagation         To observer
   Light-time algorithm      Converged Newtonian
   Stellar aberration        Corrected for stellar aberration
   Time system               UTC
   Time format               Calendar date and time
   Input time                2007 JAN 1 00:00:00
   State representation      Planetocentric
WGC will return the following longitude and latitude, deg:

   3.61310222
   -6.43834182
To compute the Moon-Earth direction using a high accuracy PCK and the MOON_ME frame, specify/select the following inputs in the ``State Vector'' calculation:

   Target                    EARTH
   Observer                  MOON
   Reference frame           MOON_ME
   Light propagation         To observer
   Light-time algorithm      Converged Newtonian
   Stellar aberration        Corrected for stellar aberration
   Time system               UTC
   Time format               Calendar date and time
   Input time                2007 JAN 1 00:00:00
   State representation      Planetocentric
WGC will return the following longitude and latitude, deg:

   3.61122841
   -6.43950148
WGC cannot compute angular separation between the Moon-Earth direction vectors in the IAU_MOON and MOON_ME frames.

To compute the Moon-Earth direction using a high accuracy PCK and the MOON_PA frame, specify/select the following inputs in the ``State Vector'' calculation:

   Target                    EARTH
   Observer                  MOON
   Reference frame           MOON_PA
   Light propagation         To observer
   Light-time algorithm      Newtonian
   Stellar aberration        Corrected for stellar aberration
   Time system               UTC
   Time format               Calendar date and time
   Input time                2007 JAN 1 00:00:00
   State representation      Planetocentric
WGC will return the following longitude and latitude, deg:

   3.59331861
   -6.41758189
WGC cannot compute angular separation between the Moon-Earth direction vectors in the MOON_ME and MOON_PA frames.

To compute the sub-Earth point on the Moon using a high accuracy PCK and the MOON_ME frame, specify/select the following inputs in the ``Sub-Observer Point'' calculation:

   Target                    MOON
   Reference frame           MOON_ME
   Observer                  EARTH
   Sub-point type            Near point on ellipsoid
   Light propagation         To observer
   Light-time algorithm      Converged Newtonian
   Stellar aberration        Corrected for stellar aberration
   Time system               UTC
   Time format               Calendar date and time
   Input time                2007 JAN 1 00:00:00
   Position representation   Planetocentric
WGC will return the following longitude and latitude, deg:

   3.61141894
   -6.43950142
To compute the sub-Earth point on the Moon using a high accuracy PCK and the MOON_PA frame, specify/select the following inputs in the ``Sub-Observer Point'' calculation:

   Target                    MOON
   Reference frame           MOON_PA
   Observer                  EARTH
   Sub-point type            Near point on ellipsoid
   Light propagation         To observer
   Light-time algorithm      Converged Newtonian
   Stellar aberration        Corrected for stellar aberration
   Time system               UTC
   Time format               Calendar date and time
   Input time                2007 JAN 1 00:00:00
   Position representation   Planetocentric
WGC will return the following longitude and latitude, deg:

   3.59350886
   -6.41758182
WGC cannot compute the distance between the sub-Earth points computed in the MOON_ME and MOON_PA frames.



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Earth rotation (erotat)



Use the ``SPICE Class - Binary PCK Lesson Kernels (Earth)'' kernel set appearing near the bottom of the ``Kernel selection:'' menu to do this step in this lesson.

To compute the Earth-Moon direction using a low accuracy PCK and the IAU_EARTH frame, specify/select the following inputs in the ``State Vector'' calculation:

   Target                    MOON
   Observer                  EARTH
   Reference frame           IAU_EARTH
   Light propagation         To observer
   Light-time algorithm      Newtonian
   Stellar aberration        Corrected for stellar aberration
   Time system               UTC
   Time format               Calendar date and time
   Input time                2007 JAN 1 00:00:00
   State representation      Planetocentric
WGC will return the following longitude and latitude, deg:

   -35.49627162
   26.41695855
To compute the Earth-Moon direction using a high accuracy PCK and the ITRF93 frame, specify/select the following inputs in the ``State Vector'' calculation:

   Target                    MOON
   Observer                  EARTH
   Reference frame           ITRF93
   Light propagation         To observer
   Light-time algorithm      Newtonian
   Stellar aberration        Corrected for stellar aberration
   Time system               UTC
   Time format               Calendar date and time
   Input time                2007 JAN 1 00:00:00
   State representation      Planetocentric
WGC will return the following longitude and latitude, deg:

   -35.55428578
   26.41915557
WGC cannot compute the separation angle between the Earth-Moon vectors in IAU_EARTH and ITRF93 frames.

WGC cannot compute the IAU_EARTH and ITRF93 +X and +Z axis separation angles.

To compute the DSS-13-Moon azimuth and elevation using a high accuracy PCK and the DSS-13_TOPO frame, specify/select the following inputs in the ``State Vector'' calculation:

   Target                    MOON
   Observer                  DSS-13
   Reference frame           DSS-13_TOPO
   Light propagation         To observer
   Light-time algorithm      Newtonian
   Stellar aberration        Corrected for stellar aberration
   Time system               UTC
   Time format               Calendar date and time
   Input time                2007 JAN 1 00:00:00
   State representation      Planetocentric
WGC will return the following longitude and latitude, deg, that are equivalent to the azimuth (AZ=-LON) and elevation (EL=LAT):

   -72.16900637
   20.68948821
To compute the sub-solar point on Earth using a low accuracy PCK and the IAU_EARTH frame, specify/select the following inputs in the ``Sub-Solar Point'' calculation:

   Target                    EARTH
   Reference frame           IAU_EARTH
   Observer                  SUN
   Sub-point type            Near point on ellipsoid
   Light propagation         To observer
   Light-time algorithm      Newtonian
   Stellar aberration        Corrected for stellar aberration
   Time system               UTC
   Time format               Calendar date and time
   Input time                2007 JAN 1 00:00:00
   Position representation   Planetocentric
WGC will return the following longitude and latitude, deg:

   -177.10053149
   -22.91037699
To compute the sub-solar point on Earth using a high accuracy PCK and the ITRF93 frame, specify/select the following inputs in the ``Sub-Solar Point'' calculation:

   Target                    EARTH
   Reference frame           ITRF93
   Observer                  SUN
   Sub-point type            Near point on ellipsoid
   Light propagation         To observer
   Light-time algorithm      Newtonian
   Stellar aberration        Corrected for stellar aberration
   Time system               UTC
   Time format               Calendar date and time
   Input time                2007 JAN 1 00:00:00
   Position representation   Planetocentric
WGC will return the following longitude and latitude, deg:

   -177.15787351
   -22.91259307
WGC cannot compute the distance between the sub-solar points computed in the IAU_EARTH and ITRF93 frames.