[Spice_discussion] RE: [Spice_announce] Geometry Engine

[Crary, Frank]

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.)

	
Frank

-----Original Message-----
From: Diane Conner [mailto:Diane.Conner at jpl.nasa.gov]
Sent: Friday, February 21, 2003 12:19 PM
To: spice at dcs04.jpl.nasa.gov
Subject: Fwd: [Spice_announce] Geometry Engine


>Date: Wed, 19 Feb 2003 09:00:33 -0800
>From: Lee Elson <Lee.Elson at jpl.nasa.gov>
>Subject: [Spice_announce] Geometry Engine
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>As part of an ongoing effort to increase the functionality of the 
>SPICE Toolkit, we at NAIF are planning the development of SPICELIB 
>routines that will allow the user to determine time windows or 
>"schedules" when certain geometric constraints are met. To make this 
>development process as efficient as possible, we'd like to determine 
>which geometric constraints would offer the most "bang for the buck" 
>in terms of useful functionality. Listed below are brief 
>descriptions of what we've come up with (in a loose arrangement of 
>decreasing priority):
>
>1)"Distance" -- determine time intervals during which the apparent 
>distance between 2 specified bodies, as viewed from a specified 
>observing body, satisfies a specified constraint (e.g. less than, 
>equal to, greater than, between values)
>
>2)"Phase"-- determine time intervals during which the apparent 
>observer-target-Sun angle satisfies a specified constraint.
>
>3)"Eclipse"-- determine time intervals during which one body is 
>eclipsed by another as viewed by an observer.
>
>4)"Occultation/transit"-- determine time intervals during which one 
>body is occulted/transited by another as viewed by an observer.
>
>5)"Time from periapsis/apoapsis"-- determine time intervals during 
>which a body in orbit is within a specified time interval from 
>periapsis/apoapsis.
>
>6)"Elevation"-- determine time intervals during which the elevation 
>of an object, in a specified reference frame, satisfies a specified 
>constraint.
>
>7)"Viewed Latitude/longitude"-- determine time intervals during 
>which a viewed location (latitude/longitude) satisfies a specified 
>constraint.
>
>8)"Nadir separation"-- determine time intervals during which the 
>angle between an observed object and the nadir direction satisfies a 
>specified constraint.
>
>9)"Separation"-- determine time intervals during which the angular 
>separation of 2 bodies (as seen by an observer) satisfies a 
>specified constraint.
>
>10)"Incidence/emission/solar longitude"-- determine time intervals 
>during which the incidence/emission/solar longitude angle satisfies 
>a specified constraint.
>
>11)"Orbital longitude"-- determine time intervals during which the 
>orbital longitude of an object, relative to an observer, satisfies a 
>specified constraint.
>
>12)"Angular velocity"-- determine time intervals during which the 
>angular velocity of one object relative to another satisfies a 
>specified constraint.
>
>13)"Apparent diameter"-- determine time intervals during which the 
>apparent diameter of a body satisfies a specified constraint.
>
>14)"Elongation"-- determine time intervals during which the 
>elongation (angular separation of a body from the sun) of a body 
>satisfies a specified constraint.
>
>15)"Relative velocity"-- determine time intervals during which the 
>velocity of one body relative to another satisfies a specified 
>constraint.
>
>16) "User supplied"-- determine time intervals during which a 
>function provided by the user satisfies a specified constraint.
>
>In addition to the time oriented "windows/schedules" discussed 
>above, it is possible (but more work) to have other solutions. An 
>example might be to find a range of viewed latitudes and longitudes 
>for a specified time window.
>
>The main purpose of this note is to solicit your input. Are the 16 
>constraints listed above of any use to you? Are there others that 
>would be more useful?
>
>Regards,
>Lee Elson
>Lee.Elson at jpl.nasa.gov
>818-354-4223
>
>
>
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>Spice_announce mailing list
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-- 
Diane Conner
--------------------------------
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