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<TITLE>RE: [Spice_announce] Geometry Engine</TITLE>
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<P><FONT SIZE=2>All of the geometric events in that list seem to involve three bodies (i.e. angular separation between body 1 and body 2, as seen from a spacecraft.) I think it would be very convenient for particles and fields instruments to have simple, 2 body events (e.g. range between spacecraft and planet body center less than X or planetocentric latitude of spacecraft greater than Y.)</FONT></P>
<P> <FONT SIZE=2>Frank</FONT>
</P>
<P><FONT SIZE=2>-----Original Message-----</FONT>
<BR><FONT SIZE=2>From: Diane Conner [<A HREF="mailto:Diane.Conner@jpl.nasa.gov">mailto:Diane.Conner@jpl.nasa.gov</A>]</FONT>
<BR><FONT SIZE=2>Sent: Friday, February 21, 2003 12:19 PM</FONT>
<BR><FONT SIZE=2>To: spice@dcs04.jpl.nasa.gov</FONT>
<BR><FONT SIZE=2>Subject: Fwd: [Spice_announce] Geometry Engine</FONT>
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<BR>
<P><FONT SIZE=2>>Date: Wed, 19 Feb 2003 09:00:33 -0800</FONT>
<BR><FONT SIZE=2>>From: Lee Elson <Lee.Elson@jpl.nasa.gov></FONT>
<BR><FONT SIZE=2>>Subject: [Spice_announce] Geometry Engine</FONT>
<BR><FONT SIZE=2>>Sender: spice_announce-admin@naif.jpl.nasa.gov</FONT>
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<BR><FONT SIZE=2>>List-Id: General SPICE announcements <spice_announce.naif.jpl.nasa.gov></FONT>
<BR><FONT SIZE=2>></FONT>
<BR><FONT SIZE=2>>As part of an ongoing effort to increase the functionality of the </FONT>
<BR><FONT SIZE=2>>SPICE Toolkit, we at NAIF are planning the development of SPICELIB </FONT>
<BR><FONT SIZE=2>>routines that will allow the user to determine time windows or </FONT>
<BR><FONT SIZE=2>>"schedules" when certain geometric constraints are met. To make this </FONT>
<BR><FONT SIZE=2>>development process as efficient as possible, we'd like to determine </FONT>
<BR><FONT SIZE=2>>which geometric constraints would offer the most "bang for the buck" </FONT>
<BR><FONT SIZE=2>>in terms of useful functionality. Listed below are brief </FONT>
<BR><FONT SIZE=2>>descriptions of what we've come up with (in a loose arrangement of </FONT>
<BR><FONT SIZE=2>>decreasing priority):</FONT>
<BR><FONT SIZE=2>></FONT>
<BR><FONT SIZE=2>>1)"Distance" -- determine time intervals during which the apparent </FONT>
<BR><FONT SIZE=2>>distance between 2 specified bodies, as viewed from a specified </FONT>
<BR><FONT SIZE=2>>observing body, satisfies a specified constraint (e.g. less than, </FONT>
<BR><FONT SIZE=2>>equal to, greater than, between values)</FONT>
<BR><FONT SIZE=2>></FONT>
<BR><FONT SIZE=2>>2)"Phase"-- determine time intervals during which the apparent </FONT>
<BR><FONT SIZE=2>>observer-target-Sun angle satisfies a specified constraint.</FONT>
<BR><FONT SIZE=2>></FONT>
<BR><FONT SIZE=2>>3)"Eclipse"-- determine time intervals during which one body is </FONT>
<BR><FONT SIZE=2>>eclipsed by another as viewed by an observer.</FONT>
<BR><FONT SIZE=2>></FONT>
<BR><FONT SIZE=2>>4)"Occultation/transit"-- determine time intervals during which one </FONT>
<BR><FONT SIZE=2>>body is occulted/transited by another as viewed by an observer.</FONT>
<BR><FONT SIZE=2>></FONT>
<BR><FONT SIZE=2>>5)"Time from periapsis/apoapsis"-- determine time intervals during </FONT>
<BR><FONT SIZE=2>>which a body in orbit is within a specified time interval from </FONT>
<BR><FONT SIZE=2>>periapsis/apoapsis.</FONT>
<BR><FONT SIZE=2>></FONT>
<BR><FONT SIZE=2>>6)"Elevation"-- determine time intervals during which the elevation </FONT>
<BR><FONT SIZE=2>>of an object, in a specified reference frame, satisfies a specified </FONT>
<BR><FONT SIZE=2>>constraint.</FONT>
<BR><FONT SIZE=2>></FONT>
<BR><FONT SIZE=2>>7)"Viewed Latitude/longitude"-- determine time intervals during </FONT>
<BR><FONT SIZE=2>>which a viewed location (latitude/longitude) satisfies a specified </FONT>
<BR><FONT SIZE=2>>constraint.</FONT>
<BR><FONT SIZE=2>></FONT>
<BR><FONT SIZE=2>>8)"Nadir separation"-- determine time intervals during which the </FONT>
<BR><FONT SIZE=2>>angle between an observed object and the nadir direction satisfies a </FONT>
<BR><FONT SIZE=2>>specified constraint.</FONT>
<BR><FONT SIZE=2>></FONT>
<BR><FONT SIZE=2>>9)"Separation"-- determine time intervals during which the angular </FONT>
<BR><FONT SIZE=2>>separation of 2 bodies (as seen by an observer) satisfies a </FONT>
<BR><FONT SIZE=2>>specified constraint.</FONT>
<BR><FONT SIZE=2>></FONT>
<BR><FONT SIZE=2>>10)"Incidence/emission/solar longitude"-- determine time intervals </FONT>
<BR><FONT SIZE=2>>during which the incidence/emission/solar longitude angle satisfies </FONT>
<BR><FONT SIZE=2>>a specified constraint.</FONT>
<BR><FONT SIZE=2>></FONT>
<BR><FONT SIZE=2>>11)"Orbital longitude"-- determine time intervals during which the </FONT>
<BR><FONT SIZE=2>>orbital longitude of an object, relative to an observer, satisfies a </FONT>
<BR><FONT SIZE=2>>specified constraint.</FONT>
<BR><FONT SIZE=2>></FONT>
<BR><FONT SIZE=2>>12)"Angular velocity"-- determine time intervals during which the </FONT>
<BR><FONT SIZE=2>>angular velocity of one object relative to another satisfies a </FONT>
<BR><FONT SIZE=2>>specified constraint.</FONT>
<BR><FONT SIZE=2>></FONT>
<BR><FONT SIZE=2>>13)"Apparent diameter"-- determine time intervals during which the </FONT>
<BR><FONT SIZE=2>>apparent diameter of a body satisfies a specified constraint.</FONT>
<BR><FONT SIZE=2>></FONT>
<BR><FONT SIZE=2>>14)"Elongation"-- determine time intervals during which the </FONT>
<BR><FONT SIZE=2>>elongation (angular separation of a body from the sun) of a body </FONT>
<BR><FONT SIZE=2>>satisfies a specified constraint.</FONT>
<BR><FONT SIZE=2>></FONT>
<BR><FONT SIZE=2>>15)"Relative velocity"-- determine time intervals during which the </FONT>
<BR><FONT SIZE=2>>velocity of one body relative to another satisfies a specified </FONT>
<BR><FONT SIZE=2>>constraint.</FONT>
<BR><FONT SIZE=2>></FONT>
<BR><FONT SIZE=2>>16) "User supplied"-- determine time intervals during which a </FONT>
<BR><FONT SIZE=2>>function provided by the user satisfies a specified constraint.</FONT>
<BR><FONT SIZE=2>></FONT>
<BR><FONT SIZE=2>>In addition to the time oriented "windows/schedules" discussed </FONT>
<BR><FONT SIZE=2>>above, it is possible (but more work) to have other solutions. An </FONT>
<BR><FONT SIZE=2>>example might be to find a range of viewed latitudes and longitudes </FONT>
<BR><FONT SIZE=2>>for a specified time window.</FONT>
<BR><FONT SIZE=2>></FONT>
<BR><FONT SIZE=2>>The main purpose of this note is to solicit your input. Are the 16 </FONT>
<BR><FONT SIZE=2>>constraints listed above of any use to you? Are there others that </FONT>
<BR><FONT SIZE=2>>would be more useful?</FONT>
<BR><FONT SIZE=2>></FONT>
<BR><FONT SIZE=2>>Regards,</FONT>
<BR><FONT SIZE=2>>Lee Elson</FONT>
<BR><FONT SIZE=2>>Lee.Elson@jpl.nasa.gov</FONT>
<BR><FONT SIZE=2>>818-354-4223</FONT>
<BR><FONT SIZE=2>></FONT>
<BR><FONT SIZE=2>></FONT>
<BR><FONT SIZE=2>></FONT>
<BR><FONT SIZE=2>>_______________________________________________</FONT>
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<BR>
<P><FONT SIZE=2>-- </FONT>
<BR><FONT SIZE=2>Diane Conner</FONT>
<BR><FONT SIZE=2>--------------------------------</FONT>
<BR><FONT SIZE=2>1.818.354.8586 voice 1.818.393.4669 Fax </FONT>
<BR><FONT SIZE=2>SPICE: <A HREF="https://cassini.jpl.nasa.gov/csos/io/spice/" TARGET="_blank">https://cassini.jpl.nasa.gov/csos/io/spice/</A></FONT>
<BR><FONT SIZE=2>SPICE FILES: <A HREF="ftp://naif.jpl.nasa.gov/pub/naif/CASSINI/kernels/" TARGET="_blank">ftp://naif.jpl.nasa.gov/pub/naif/CASSINI/kernels/</A></FONT>
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