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Brief Guide to Doing SPICE Hands-On Lessons Using WGC

   Brief Guide to Doing SPICE Hands-On Lessons Using WGC
      Overview
         WGC and WGC Tutorial URLs
      ``CASSINI Remote Sensing'' Hands-On Lesson Using WGC
         Kernels Used
         Time Conversion (convtm)
         Time Conversion -- Selected Extra Credit
         Obtaining Target States and Positions (getsta)
         Obtaining Target States and Positions -- Selected Extra Credit
         Spacecraft Orientation and Reference Frames (xform)
         Spacecraft Orientation and Reference Frames -- Selected Extra Credit
         Computing Sub-s/c and Sub-solar Points on an Ellipsoid and a DSK (subpts)
         Computing Sub-spacecraft and Sub-solar Points -- Selected Extra Credit
         Intersecting Vectors with an Ellipsoid and a DSK (fovint)
      ``ExoMars 2016 Remote Sensing'' Hands-On Lesson Using WGC
         Kernels Used
         Time Conversion (convtm)
         Time Conversion -- Selected Extra Credit
         Obtaining Target States and Positions (getsta)
         Obtaining Target States and Positions -- Selected Extra Credit
         Spacecraft Orientation and Reference Frames (xform)
         Spacecraft Orientation and Reference Frames -- Selected Extra Credit
         Computing Sub-s/c and Sub-solar Points on an Ellipsoid and a DSK (subpts)
         Computing Sub-spacecraft and Sub-solar Points -- Selected Extra Credit
         Intersecting Vectors with an Ellipsoid and a DSK (fovint)
      ``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''
      ``Mars Express Geometric Event Finding'' Hands-On Lesson Using WGC
         Kernels Used
         Find View Periods
         Find Times when Target is Visible
         Extra Credit
      ``ExoMars-16 TGO Geometric Event Finding'' Hands-On Lesson Using WGC
         Kernels Used
         Find View Periods
         Find Times when Target is Visible
         Extra Credit
      ``Binary PCK'' Hands-On Lesson Using WGC
         Moon rotation (mrotat)
         Earth rotation (erotat)

Brief Guide to Doing SPICE Hands-On Lessons Using WGC

May 21, 2018

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Overview

This guide provides brief instructions on how to do SPICE ``Remote Sensing'' (CASSINI and ExoMars 2016), ``In-situ Sensing'', ``Geometric Event Finding'' (Mars Express and ExoMars 2016), 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 at NAIF can be accessed at:

   http://wgc.jpl.nasa.gov:8080/webgeocalc/#NewCalculation

WGC at ESAC can be accessed at:

   http://spice.esac.esa.int/webgeocalc/#NewCalculation

The WGC tutorial and examples are linked from the WGC introduction page on the NAIF server:

   https://naif.jpl.nasa.gov/naif/webgeocalc.html

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

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Kernels Used

Use the ``SPICE Class - CASSINI 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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Time Conversion -- Selected Extra Credit

1. To compute TDB Julian Date, 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        Julian Date

WGC will return the following SCLK time string:

   2453168.314631800 JD TDB

5. To compute the earliest UTC time that can be converted to CASSINI spacecraft clock, specify/select the following inputs in the ``Time Conversion'' calculation:

   Time system               Spacecraft clock (SCLK=-82)
   Time format               Spacecraft clock ticks
   Input time                0.0
   Output time system        UTC
   Output time format        Calendar (year-month-day)

WGC will return the following UTC time string:

   1980-01-01 00:00:00.000000 UTC

6. To convert the spacecraft clock time obtained in the regular task back to UTC Time and present it in ISO calendar date format, with a resolution of milliseconds, specify/select the following inputs in the ``Time Conversion'' calculation:

   Time system               Spacecraft clock (SCLK=-82)
   Time format               Spacecraft clock string
   Input time                1/1465674964.105
   Output time system        UTC
   Custom format             YYYY-MM-DDTHR:MN:SC.### ::RND

WGC will return the following UTC time string:

   2004-06-11T19:31:59.999

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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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Obtaining Target States and Positions -- Selected Extra Credit

5. To compute the position of the Sun as seen from Saturn in the J2000 using the following light time and aberration corrections: NONE, LT and LT+S, manually load the additional SPK used in the hands-on lesson (generic_kernels/spk/satellites/a_old_versions/jup310_2004.bsp) and specify/select the following inputs in the ``State Vector'' calculation (except for corrections):

   Target                    SUN
   Observer                  SATURN
   Reference frame           J2000
   Time system               UTC
   Time format               Calendar date and time
   Input time                2004 JUN 11 19:32:00
   State representation      Rectangular

and these corrections for NONE (the geometric position), LT (the reception light time only corrected position), and LT+S (the apparent position):

   Light propagation         No correction
 
   Light propagation         To observer
   Light-time algorithm      Newtonian
 
   Light propagation         To observer
   Light-time algorithm      Newtonian
   Stellar aberration        Corrected for stellar aberration

WGC will return the following position vectors, km, correspondingly:

   367770592.36738380
   -1197330367.35880470
   -510369088.67673343
 
   367770572.92069393
   -1197330417.73307600
   -510369109.50883270
 
   367726456.16774523
   -1197342627.87914750
   -510372252.74684080

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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

To compute the angular separation between the apparent position of Earth and the CASSINI high gain antenna (HGA) 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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Spacecraft Orientation and Reference Frames -- Selected Extra Credit

2. To compute the angular separation between the apparent position of Sun and the CASSINI HGA nominal boresight to find out if HGA is illuminated, specify/select the following inputs in the ``State Vector'' calculation:

   Target                    SUN
   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                2018 JUN 11 19:32:00
   State representation      Spherical

WGC will return the following output colatitude, deg:

   73.12975130

This angle is less than 90 degrees so the HGA is illuminated.

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Computing Sub-s/c and Sub-solar Points on an Ellipsoid and a DSK (subpts)

To compute the apparent sub-observer point of CASSINI on Phoebe modeled as an ellipsoid 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 modeled as an ellipsoid 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

WGC cannot compute the sub-spacecraft and sub-solar points on a DSK.

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Computing Sub-spacecraft and Sub-solar Points -- Selected Extra Credit

1. To compute the apparent sub-solar point on Phoebe as seen from CASSINI in the IAU_PHOEBE frame using the ``Intercept: ellipsoid'' method, 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            Intercept 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                2018 JUN 11 19:32:00
   Position representation   Rectangular

WGC will return the following position vector, km:

   74.54229300
   79.60686277
   -24.87078454

2. To compute the geometric sub-observer point of CASSINI on Phoebe in the IAU_PHOEBE frame using the 'Near point: ellipsoid' method, specify/select the following inputs in the ``Sub-Observer Point'' calculation:

   Calculation type          Sub-Observer Point
   Target                    PHOEBE
   Reference frame           IAU_PHOEBE
   Observer                  CASSINI
   Sub-point type            Near point on ellipsoid
   Light propagation         No correction
   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:

   104.49708353
   45.27041148
   7.38409174

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

   Calculation type          Sub-Observer Point
   Target                    PHOEBE
   Reference frame           IAU_PHOEBE
   Observer                  CASSINI
   Sub-point type            Near point on ellipsoid
   Light propagation         No correction
   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 latitude and longitude, deg, and radius, km:

   3.70986500
   23.42331102
   114.12088079

WGC does not allow computing planetodetic and planetographic coordinates on bodies that are tri-axial ellipsoids with different equatorial radii. Choosing the planetographic coordinates for output will result in the following error message:

   Reference frame center is not a spheroid. Planetodetic and
   planetographic coordinate representations can only be
   calculated for bodies with equal equatorial axes. The center
   body of the reference frame, PHOEBE, has equatorial axes
   that differ, 115.0 and 110.0. Use planetocentric coordinates
   instead.

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Intersecting Vectors with an Ellipsoid and a DSK (fovint)

To compute the Cartesian position vectors of the FOV boundary vector surface intercept points on the surface of Phoebe modeled as an ellipsoid 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
 
   89.99095003
   66.72560204
   14.73282379
 
   80.96314734
   76.64306316
   14.42662102
 
   81.99683969
   77.10572511
   1.69850758

To compute the planetocentric longitudes and latitudes of the FOV boundary vector surface intercept points on the surface of Phoebe modeled as an ellipsoid 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 on the surface of Phoebe modeled as an ellipsoid 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 on the surface of Phoebe modeled as an ellipsoid 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 surface intercept points on a DSK and the local solar time at the boresight intercept point.

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``ExoMars 2016 Remote Sensing'' Hands-On Lesson Using WGC

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Kernels Used

Use the ``SPICE Class - ExoMars 2016 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                2018 jun 11 19:32:00
   Output time system        TDB
   Output time format        Seconds past J2000

WGC will return the following ET seconds past J2000:

   582017589.184640

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                2018 jun 11 19:32:00
   Output time system        TDB
   Output time format        Calendar (year-month-day)

WGC will return the following calendar ET time string:

   2018-06-11 19:33:09.184642

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                2018 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:

   2018-JUN-11T19:33:09

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                2018 jun 11 19:32:00
   Output time system        Spacecraft clock (SCLK=-143)
   Output time format        Spacecraft clock string

WGC will return the following SCLK time string:

   1/0070841719.26698

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Time Conversion -- Selected Extra Credit

1. To compute TDB Julian Date, specify/select the following inputs in the ``Time Conversion'' calculation:

   Time system               UTC
   Time format               Calendar date and time
   Input time                2018 jun 11 19:32:00
   Output time system        TDB
   Output time format        Julian Date

WGC will return the following SCLK time string:

   2458281.314689600 JD TDB

5. To compute the earliest UTC time that can be converted to ExoMars-16 TGO spacecraft clock, specify/select the following inputs in the ``Time Conversion'' calculation:

   Time system               Spacecraft clock (SCLK=-143)
   Time format               Spacecraft clock ticks
   Input time                0.0
   Output time system        UTC
   Output time format        Calendar (year-month-day)

WGC will return the following UTC time string:

   2016-03-13 21:34:13.193650 UTC

   Time system               Spacecraft clock (SCLK=-143)
   Time format               Spacecraft clock string
   Input time                1/0070841719.26698
   Output time system        UTC
   Custom format             YYYY-MM-DDTHR:MN:SC.### ::RND

WGC will return the following UTC time string:

   2018-06-11T19:32:00.000

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Obtaining Target States and Positions (getsta)

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

   Target                    MARS
   Observer                  EXOMARS 2016 TGO
   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                2018 JUN 11 19:32:00
   State representation      Rectangular

WGC will return the following state vector, km and km/s:

   2911.82242547
   -2033.80245966
   -1291.70085522
   1.30950490
   -0.05597018
   3.10432898

To compute the apparent position of Earth as seen from TGO in the J2000 frame and one way light time between TGO and the apparent position of Earth, specify/select the following inputs in the ``State Vector'' calculation:

   Target                    EARTH
   Observer                  EXOMARS 2016 TGO
   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                2018 JUN 11 19:32:00
   State representation      Rectangular

WGC will return the following position vector, km, and one way light time, s:

   -49609884.08045448
   57070665.86178913
   30304236.92973865
   271.73803215

To compute the apparent position of Sun as seen from Mars in the J2000 frame, specify/select the following inputs in the ``State Vector'' calculation:

   Target                    SUN
   Observer                  MARS
   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                2018 JUN 11 19:32:00
   State representation      Rectangular

WGC will return the following position vector, km:

   -24712734.28893231
   194560532.94319060
   89906636.78934350

Note that WGC will also compute the distance between Sun and Mars body centers, km:

   215749214.49206870

but it cannot convert this distance to AUs.

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Obtaining Target States and Positions -- Selected Extra Credit

4. To compute the position of the Sun as seen from Mars in the J2000 using the following light time and aberration corrections: NONE, LT and LT+S, specify/select the following inputs in the ``State Vector'' calculation (except for corrections):

   Target                    SUN
   Observer                  MARS
   Reference frame           J2000
   Time system               UTC
   Time format               Calendar date and time
   Input time                2018 JUN 11 19:32:00
   State representation      Rectangular

and these corrections for NONE (the geometric position), LT (the reception light time only corrected position), and LT+S (the apparent position):

   Light propagation         No correction
 
   Light propagation         To observer
   Light-time algorithm      Newtonian
 
   Light propagation         To observer
   Light-time algorithm      Newtonian
   Stellar aberration        Corrected for stellar aberration

WGC will return the following position vectors, km, correspondingly:

   -24730875.20069792
   194558449.55971023
   89906170.85450794
 
   -24730866.48857886
   194558445.24649155
   89906168.75352160
 
   -24712734.28893231
   194560532.94319060
   89906636.78934350

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Spacecraft Orientation and Reference Frames (xform)

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

   Target                    MARS
   Observer                  EXOMARS 2016 TGO
   Reference frame           IAU_MARS
   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                2018 JUN 11 19:32:00
   State representation      Rectangular

WGC will return the following state vector, km and km/s:

   -2843.46412456
   2235.45954373
   1095.89496870
   0.31144328
   -1.15192925
   3.08212262

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. Since the nominal instrument view direction is the ``-Y'' axis of the ``TGO_SPACECRAFT'' frame we cannot use this approach with this frame but we can use it with the ``TGO_NOMAD_LNO_NAD'' frame which has its ``Z'' axis along the view direction.

To compute the angular separation between the apparent position of Mars and the TGO nominal instrument view direction, specify/select the following inputs in the ``State Vector'' calculation:

   Target                    MARS
   Observer                  EXOMARS 2016 TGO
   Reference frame           TGO_NOMAD_LNO_NAD
   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                2018 JUN 11 19:32:00
   State representation      Spherical

WGC will return the following output colatitude, deg:

   5.43847143

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Spacecraft Orientation and Reference Frames -- Selected Extra Credit

2. To compute the angular separation between the apparent position of Sun and the TGO nominal instrument view direction to find out if the science deck illuminated, specify/select the following inputs in the ``State Vector'' calculation:

   Target                    SUN
   Observer                  EXOMARS 2016 TGO
   Reference frame           TGO_NOMAD_LNO_NAD
   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                2018 JUN 11 19:32:00
   State representation      Spherical

WGC will return the following output colatitude, deg:

   130.54279733

This angle is greater than 90 degrees so the science deck is not illuminated.

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Computing Sub-s/c and Sub-solar Points on an Ellipsoid and a DSK (subpts)

To compute the apparent sub-observer point of TGO on Mars in the IAU_MARS frame using the ``Near point: ellipsoid'' method, specify/select the following inputs in the ``Sub-Observer Point'' calculation:

   Target                    MARS
   Reference frame           IAU_MARS
   Observer                  EXOMARS 2016 TGO
   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                2018 JUN 11 19:32:00
   Position representation   Rectangular

WGC will return the following position vector, km:

   2554.16465516
   -2008.01038262
   -983.24042077

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:

   385.04529279

To compute the apparent sub-solar point on Mars as seen from TGO in the IAU_MARS frame using the ``Near point: ellipsoid'' method, specify/select the following inputs in the ``Sub-Solar Point'' calculation:

   Calculation type          Sub-Solar Point
   Target                    MARS
   Reference frame           IAU_MARS
   Observer                  EXOMARS 2016 TGO
   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                2018 JUN 11 19:32:00
   Position representation   Rectangular

WGC will return the following position vector, km:

   487.58869797
   -3348.61049793
   -286.69722014

WGC cannot compute the sub-spacecraft and sub-solar points on a DSK.

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Computing Sub-spacecraft and Sub-solar Points -- Selected Extra Credit

1. To compute the apparent sub-solar point on Mars as seen from TGO in the IAU_MARS frame using the ``Intercept: ellipsoid'' method, specify/select the following inputs in the ``Sub-Solar Point'' calculation:

   Calculation type          Sub-Solar Point
   Target                    MARS
   Reference frame           IAU_MARS
   Observer                  EXOMARS 2016 TGO
   Sub-point type            Intercept 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                2018 JUN 11 19:32:00
   Position representation   Rectangular

WGC will return the following position vector, km:

   487.54669671
   -3348.32205372
   -290.07721511

2. To compute the apparent sub-observer point of TGO on Phobos in the IAU_PHOBOS frame using the 'Near point: ellipsoid' method, specify/select the following inputs in the ``Sub-Observer Point'' calculation:

   Target                    PHOBOS
   Reference frame           IAU_PHOBOS
   Observer                  EXOMARS 2016 TGO
   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                2018 JUN 11 19:32:00
   Position representation   Rectangular

WGC will return the following position vector, km:

   12.05913904
   4.17308831
   -0.67546616

3. To compute the planetocentric coordinates of the apparent sub-observer point of TGO on Phobos in the IAU_PHOBOS frame using the 'Near point: ellipsoid' method, specify/select the following inputs in the ``Sub-Observer Point'' calculation:

   Target                    PHOBOS
   Reference frame           IAU_PHOBOS
   Observer                  EXOMARS 2016 TGO
   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                2018 JUN 11 19:32:00
   Position representation   Planetocentric

WGC will return the following latitude and longitude, deg, and radius, km:

   -3.03000878
   19.08827715
   12.77864449

   Reference frame center is not a spheroid. Planetodetic and
   planetographic coordinate representations can only be
   calculated for bodies with equal equatorial axes. The center
   body of the reference frame, PHOBOS, has equatorial axes
   that differ, 13.0 and 11.4. Use planetocentric coordinates
   instead.

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Intersecting Vectors with an Ellipsoid and a DSK (fovint)

To compute the Cartesian position vectors of the FOV boundary vector surface intercept points on the surface of Mars modeled as an ellipsoid in the IAU_MARS frame, specify/select the following inputs in the ``Surface Intercept Point'' calculation:

   Target                    MARS
   Reference frame           IAU_MARS
   Observer                  EXOMARS 2016 TGO
   Ray vector                TGO_NOMAD_LNO_NAD
                             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                2018 JUN 11 19:32:00
   Position representation   Rectangular

WGC will return the following position vectors, km:

   2535.00445179
   -2028.52838809
   -990.59432639
 
   2525.05593461
   -2042.07461651
   -988.19646467
 
   2525.20138167
   -2042.10358036
   -987.76992477
 
   2535.14886773
   -2028.55774855
   -990.16957287

To compute the planetocentric longitudes and latitudes of the FOV boundary vector surface intercept points on the surface of Mars modeled as an ellipsoid in the IAU_MARS frame, specify/select the following inputs in the ``Surface Intercept Point'' calculation:

   Target                    MARS
   Reference frame           IAU_MARS
   Observer                  EXOMARS 2016 TGO
   Ray vector                TGO_NOMAD_LNO_NAD
                             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                2018 JUN 11 19:32:00
   Position representation   Planetocentric

WGC will return the following longitudes and latitudes, deg:

   -38.66704048
   -16.96728341
 
   -38.96331703
   -16.92492977
 
   -38.96210076
   -16.91739679
 
   -38.66585276
   -16.95978024

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 on the surface of Mars modeled as an ellipsoid in the IAU_MARS frame, specify/select the following inputs in the ``Surface Intercept Point'' calculation:

   Target                    MARS
   Reference frame           IAU_MARS
   Observer                  EXOMARS 2016 TGO
   Ray vector                TGO_NOMAD_LNO_NAD 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                2018 JUN 11 19:32:00
   Position representation   Rectangular

WGC will return the following position vector, km:

   2530.12229730
   -2035.30663798
   -989.18816471

To compute the planetocentric longitude and latitude of the FOV boresight surface intercept point on the surface of Mars modeled as an ellipsoid in the IAU_MARS frame and the illumination angles at this point, specify/select the following inputs in the ``Surface Intercept Point'' calculation:

   Target                    MARS
   Reference frame           IAU_MARS
   Observer                  EXOMARS 2016 TGO
   Ray vector                TGO_NOMAD_LNO_NAD 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                2018 JUN 11 19:32:00
   Position representation   Planetocentric

WGC will return the following longitude and latitude, deg:

   -38.81424755
   -16.94244506

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

   43.72871855
   6.08637448
   49.45727680

WGC cannot compute the surface intercept points on a DSK and the local solar time at the boresight intercept point.

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``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 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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``Mars Express Geometric Event Finding'' Hands-On Lesson Using WGC

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Kernels Used

Use the ``SPICE Class - Mars Express 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 is not occulted by Mars modeled as an ellipsoid, 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 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

WGC cannot compute occultations by a body with the surface modeled by a DSK.

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Extra Credit

1. To find times when Mars Express orbiter (MEX) crosses Mars' equator, specify/select the following inputs in the ``Position Event Finder'' calculation:

   Target                      MARS EXPRESS
   Observer                    MARS
   Reference frame             IAU_MARS
   Light propagation           No correction
   Time system                 TDB
   Time format                 Calendar date and time
   Time range                  2004 MAY 02 to 2004 MAY 06,
                               step 300 seconds
   Coordinate condition        Latitude equals 0
   Output time unit            seconds
   Complement result window    no
   Result interval adjustment  No adjustment
   Result interval filtering   No filtering

WGC will return the following times:

   2004-05-02 05:00:08.334792 TDB
   2004-05-02 06:15:13.074957 TDB
   2004-05-02 12:35:14.856242 TDB
   2004-05-02 13:50:09.161841 TDB
   2004-05-02 20:10:24.439170 TDB
   2004-05-02 21:25:10.344246 TDB
   2004-05-03 03:45:26.758446 TDB
   2004-05-03 05:00:04.086901 TDB
   2004-05-03 11:20:32.419618 TDB
   2004-05-03 12:34:57.968562 TDB
   2004-05-03 18:55:34.883629 TDB
   2004-05-03 20:09:53.063063 TDB
   2004-05-04 02:30:35.509603 TDB
   2004-05-04 03:44:42.753445 TDB
   2004-05-04 10:05:41.638033 TDB
   2004-05-04 11:19:38.397433 TDB
   2004-05-04 17:40:41.405725 TDB
   2004-05-04 18:54:31.413477 TDB
   2004-05-05 01:15:45.967991 TDB
   2004-05-05 02:29:25.294886 TDB
   2004-05-05 08:50:53.931352 TDB
   2004-05-05 10:04:26.915886 TDB
   2004-05-05 16:25:58.350272 TDB
   2004-05-05 17:39:23.889937 TDB

2. To find times when Mars Express orbiter (MEX) is at periapsis, specify/select the following inputs in the ``Distance Event Finder'' calculation:

   Target                      MARS EXPRESS
   Observer                    MARS
   Light propagation           No correction
   Time system                 TDB
   Time format                 Calendar date and time
   Time range                  2004 MAY 02 to 2004 MAY 06,
                               step 300 seconds
   Coordinate condition        is local minimum
   Output time unit            seconds
   Complement result window    no
   Result interval adjustment  No adjustment
   Result interval filtering   No filtering

WGC will return the following times:

   2004-05-02 05:57:51.000411 TDB
   2004-05-02 13:32:43.325958 TDB
   2004-05-02 21:07:41.124293 TDB
   2004-05-03 04:42:30.648154 TDB
   2004-05-03 12:17:21.143198 TDB
   2004-05-03 19:52:12.267643 TDB
   2004-05-04 03:26:57.755816 TDB
   2004-05-04 11:01:49.826895 TDB
   2004-05-04 18:36:38.448012 TDB
   2004-05-05 02:11:28.558226 TDB
   2004-05-05 09:46:26.309109 TDB
   2004-05-05 17:21:18.875493 TDB

3. To find times when Mars Express orbiter (MEX) is at apoapsis, specify/select the following inputs in the ``Distance Event Finder'' calculation:

   Target                      MARS EXPRESS
   Observer                    MARS
   Light propagation           No correction
   Time system                 TDB
   Time format                 Calendar date and time
   Time range                  2004 MAY 02 to 2004 MAY 06,
                               step 300 seconds
   Coordinate condition        is local maximum
   Output time unit            seconds
   Complement result window    no
   Result interval adjustment  No adjustment
   Result interval filtering   No filtering

WGC will return the following times:

   2004-05-02 02:10:24.948283 TDB
   2004-05-02 09:45:19.189323 TDB
   2004-05-02 17:20:14.194854 TDB
   2004-05-03 00:55:07.633360 TDB
   2004-05-03 08:29:57.890652 TDB
   2004-05-03 16:04:48.524492 TDB
   2004-05-03 23:39:36.745574 TDB
   2004-05-04 07:14:25.662870 TDB
   2004-05-04 14:49:15.904704 TDB
   2004-05-04 22:24:05.351784 TDB
   2004-05-05 05:58:59.270665 TDB
   2004-05-05 13:33:54.433201 TDB
   2004-05-05 21:08:50.211003 TDB

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``ExoMars-16 TGO Geometric Event Finding'' Hands-On Lesson Using WGC

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Kernels Used

Use the ``SPICE Class - ExoMars 2016 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 ExoMars-16 TGO (TGO) is visible from the ESA station NEW_NORCIA, specify/select the following inputs in the ``Position Event Finder'' calculation:

   Target                      EXOMARS 2016 TGO
   Observer                    NEW_NORCIA
   Reference frame             NEW_NORCIA_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                  2018 JUN 10 to 2018 JUN 14,
                               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:

   2018-06-10 00:00:00.000000 TDB
   2018-06-10 02:11:17.355621 TDB
 
   2018-06-10 13:19:58.777464 TDB
   2018-06-11 02:08:16.008548 TDB
 
   2018-06-11 13:16:50.542539 TDB
   2018-06-12 02:05:12.548825 TDB
 
   2018-06-12 13:13:38.573032 TDB
   2018-06-13 02:02:06.618874 TDB
 
   2018-06-13 13:10:23.432464 TDB
   2018-06-14 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 ExoMars-16 TGO Orbiter (TGO) spacecraft is visible from the ESA station NEW_NORCIA and and is not occulted by Mars modeled as an ellipsoid, 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                   EXOMARS 2016 TGO
   Back body shape             Point
   Back body frame
   Observer                    NEW_NORCIA
   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

WGC will return the following interval start and stop times:

   2018-06-10 00:00:00.000000 TDB
   2018-06-10 01:00:30.640614 TDB
 
   2018-06-10 01:41:03.610048 TDB
   2018-06-10 02:11:17.355621 TDB
 
   2018-06-10 13:28:28.785788 TDB
   2018-06-10 14:45:38.197853 TDB
 
   2018-06-10 15:26:21.981505 TDB
   2018-06-10 16:43:32.192863 TDB
 
   2018-06-10 17:24:17.290058 TDB
   2018-06-10 18:41:27.535612 TDB
 
   2018-06-10 19:22:13.628023 TDB
   2018-06-10 20:39:21.785693 TDB
 
   2018-06-10 21:20:08.856427 TDB
   2018-06-10 22:37:12.445420 TDB
 
   2018-06-10 23:18:00.834325 TDB
   2018-06-11 00:35:01.034340 TDB
 
   2018-06-11 01:15:50.883961 TDB
   2018-06-11 02:08:16.008548 TDB
 
   2018-06-11 13:16:50.542539 TDB
   2018-06-11 14:20:09.789544 TDB
 
   2018-06-11 15:01:08.370780 TDB
   2018-06-11 16:18:03.385855 TDB
 
   2018-06-11 16:59:03.014503 TDB
   2018-06-11 18:15:58.739454 TDB
 
   2018-06-11 18:56:59.199542 TDB
   2018-06-11 20:13:54.308303 TDB
 
   2018-06-11 20:54:55.301168 TDB
   2018-06-11 22:11:47.045226 TDB
 
   2018-06-11 22:52:48.925002 TDB
   2018-06-12 00:09:35.868266 TDB
 
   2018-06-12 00:50:39.046685 TDB
   2018-06-12 02:05:12.548825 TDB
 
   2018-06-12 13:13:38.573032 TDB
   2018-06-12 13:54:43.524958 TDB
 
   2018-06-12 14:35:54.054008 TDB
   2018-06-12 15:52:36.256662 TDB
 
   2018-06-12 16:33:47.502777 TDB
   2018-06-12 17:50:30.988537 TDB
 
   2018-06-12 18:31:42.896589 TDB
   2018-06-12 19:48:26.827964 TDB
 
   2018-06-12 20:29:39.039169 TDB
   2018-06-12 21:46:20.933464 TDB
 
   2018-06-12 22:27:33.596215 TDB
   2018-06-12 23:44:11.473471 TDB
 
   2018-06-13 00:25:24.992296 TDB
   2018-06-13 01:42:00.777360 TDB
 
   2018-06-13 13:10:23.432464 TDB
   2018-06-13 13:29:19.789157 TDB
 
   2018-06-13 14:10:38.985039 TDB
   2018-06-13 15:27:11.882834 TDB
 
   2018-06-13 16:08:31.566611 TDB
   2018-06-13 17:25:06.068241 TDB
 
   2018-06-13 18:06:26.219824 TDB
   2018-06-13 19:23:01.820444 TDB
 
   2018-06-13 20:04:22.175372 TDB
   2018-06-13 21:20:57.296111 TDB
 
   2018-06-13 22:02:17.650959 TDB
   2018-06-13 23:18:49.624491 TDB

WGC cannot compute occultations by a body with the surface modeled by a DSK.

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Extra Credit

1. To find times when ExoMars-16 TGO (TGO) crosses Mars' equator, specify/select the following inputs in the ``Position Event Finder'' calculation:

   Target                      EXOMARS 2016 TGO
   Observer                    MARS
   Reference frame             IAU_MARS
   Light propagation           No correction
   Time system                 TDB
   Time format                 Calendar date and time
   Time range                  2018 JUN 10 to 2018 JUN 11,
                               step 300 seconds
   Coordinate condition        Latitude equals 0
   Output time unit            seconds
   Complement result window    no
   Result interval adjustment  No adjustment
   Result interval filtering   No filtering

WGC will return the following times:

   2018-06-10 00:14:08.836580 TDB
   2018-06-10 01:12:34.582095 TDB
   2018-06-10 02:12:00.375370 TDB
   2018-06-10 03:10:28.808573 TDB
   2018-06-10 04:09:53.955311 TDB
   2018-06-10 05:08:23.919392 TDB
   2018-06-10 06:07:48.630669 TDB
   2018-06-10 07:06:17.539430 TDB
   2018-06-10 08:05:42.659963 TDB
   2018-06-10 09:04:09.120521 TDB
   2018-06-10 10:03:34.270188 TDB
   2018-06-10 11:01:59.269625 TDB
   2018-06-10 12:01:22.866520 TDB
   2018-06-10 12:59:49.352117 TDB
   2018-06-10 13:59:13.289772 TDB
   2018-06-10 14:57:41.242004 TDB
   2018-06-10 15:57:07.576976 TDB
   2018-06-10 16:55:35.266038 TDB
   2018-06-10 17:55:02.773235 TDB
   2018-06-10 18:53:30.271499 TDB
   2018-06-10 19:52:56.383285 TDB
   2018-06-10 20:51:23.966229 TDB
   2018-06-10 21:50:47.729319 TDB
   2018-06-10 22:49:14.385397 TDB
   2018-06-10 23:48:37.583974 TDB

2. To find times when ExoMars-16 TGO (TGO) is at periapsis, specify/select the following inputs in the ``Distance Event Finder'' calculation:

   Target                      EXOMARS 2016 TGO
   Observer                    MARS
   Light propagation           No correction
   Time system                 TDB
   Time format                 Calendar date and time
   Time range                  2018 JUN 10 to 2018 JUN 11,
                               step 300 seconds
   Coordinate condition        is local minimum
   Output time unit            seconds
   Complement result window    no
   Result interval adjustment  No adjustment
   Result interval filtering   No filtering

WGC will return the following times:

   2018-06-10 00:43:06.357819 TDB
   2018-06-10 02:40:47.168872 TDB
   2018-06-10 04:38:45.496250 TDB
   2018-06-10 06:36:32.706773 TDB
   2018-06-10 08:34:10.548681 TDB
   2018-06-10 10:31:49.108636 TDB
   2018-06-10 12:29:20.342207 TDB
   2018-06-10 14:27:07.089996 TDB
   2018-06-10 16:25:36.081463 TDB
   2018-06-10 18:24:02.653942 TDB
   2018-06-10 20:22:23.184793 TDB
   2018-06-10 22:20:12.453735 TDB

3. To find times when ExoMars-16 TGO (TGO) is at apoapsis, specify/select the following inputs in the ``Distance Event Finder'' calculation:

   Target                      EXOMARS 2016 TGO
   Observer                    MARS
   Light propagation           No correction
   Time system                 TDB
   Time format                 Calendar date and time
   Time range                  2018 JUN 10 to 2018 JUN 11,
                               step 300 seconds
   Coordinate condition        is local maximum
   Output time unit            seconds
   Complement result window    no
   Result interval adjustment  No adjustment
   Result interval filtering   No filtering

WGC will return the following times:

   2018-06-10 01:41:44.632145 TDB
   2018-06-10 03:39:31.106999 TDB
   2018-06-10 05:37:22.115251 TDB
   2018-06-10 07:34:59.674318 TDB
   2018-06-10 09:32:25.708394 TDB
   2018-06-10 11:29:47.945538 TDB
   2018-06-10 13:27:30.200636 TDB
   2018-06-10 15:26:02.524463 TDB
   2018-06-10 17:24:37.842993 TDB
   2018-06-10 19:23:11.265220 TDB
   2018-06-10 21:21:13.530306 TDB
   2018-06-10 23:18:56.796575 TDB

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``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.

Table of Contents

Brief Guide to Doing SPICE Hands-On Lessons Using WGC

Overview

WGC and WGC Tutorial URLs

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

Kernels Used

Time Conversion (convtm)

Time Conversion -- Selected Extra Credit

Obtaining Target States and Positions (getsta)

Obtaining Target States and Positions -- Selected Extra Credit

Spacecraft Orientation and Reference Frames (xform)

Spacecraft Orientation and Reference Frames -- Selected Extra Credit

Computing Sub-s/c and Sub-solar Points on an Ellipsoid and a DSK (subpts)

Computing Sub-spacecraft and Sub-solar Points -- Selected Extra Credit

Intersecting Vectors with an Ellipsoid and a DSK (fovint)

``ExoMars 2016 Remote Sensing'' Hands-On Lesson Using WGC

Kernels Used

Time Conversion (convtm)

Time Conversion -- Selected Extra Credit

Obtaining Target States and Positions (getsta)

Obtaining Target States and Positions -- Selected Extra Credit

Spacecraft Orientation and Reference Frames (xform)

Spacecraft Orientation and Reference Frames -- Selected Extra Credit

Computing Sub-s/c and Sub-solar Points on an Ellipsoid and a DSK (subpts)

Computing Sub-spacecraft and Sub-solar Points -- Selected Extra Credit

Intersecting Vectors with an Ellipsoid and a DSK (fovint)

``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''

``Mars Express Geometric Event Finding'' Hands-On Lesson Using WGC

Kernels Used

Find View Periods

Find Times when Target is Visible

Extra Credit

``ExoMars-16 TGO Geometric Event Finding'' Hands-On Lesson Using WGC

Kernels Used

Find View Periods

Find Times when Target is Visible

Extra Credit

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

Moon rotation (mrotat)

Earth rotation (erotat)