Main Page 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
          ``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)
Top # Brief Guide to Doing SPICE Hands-On Lessons Using WGC May 21, 2018 Top ## 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. Top ### 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:
       http://naif.jpl.nasa.gov/naif/webgeocalc.html
Top ## ``CASSINI Remote Sensing'' Hands-On Lesson Using WGC Top ### 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. Top ### 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
Top ### 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
Top ### 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. Top ### 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
Top ### 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 (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
Top ### 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. Top ### 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. Top ### 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.
Top ### 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. Top ## ``ExoMars 2016 Remote Sensing'' Hands-On Lesson Using WGC Top ### 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. Top ### 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
Top ### 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
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=-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
Top ### 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. Top ### 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
Top ### 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
Top ### 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. Top ### 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. Top ### 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
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, PHOBOS, has equatorial axes
       that differ, 13.0 and 11.4. Use planetocentric coordinates
       instead.
Top ### 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. Top ## ``In-situ Sensing'' Hands-On Lesson Using WGC Top ### 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. Top ### 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
Top ### 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. Top ### 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
Top ### 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
Top ### 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. Top ### 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. Top ## ``Mars Express Geometric Event Finding'' Hands-On Lesson Using WGC Top ### 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. Top ### 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. Top ### 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. Top ### 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
Top ## ``ExoMars-16 TGO Geometric Event Finding'' Hands-On Lesson Using WGC Top ### 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. Top ### 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. Top ### 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
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:
       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. Top ### 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
Top ## ``Binary PCK'' Hands-On Lesson Using WGC Top ### 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. Top ### 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.