CASPER allows the user to design, visualize, and save Cassini observations.  These observations are individually called "Modules."  CASPER will now (new to Version 3.7) simulate the Cassini on-board Inertial Vector Propagation (IVP) capabilities which allow modules to be defined relative to a moving target, such as Titan, or a point in Saturn's atmosphere.  The modules with "_IVP" as the suffix allow for this capability, while most others are defined and computed relative to inertial space.  Some, such as BODMOS and PSCAN, track the target body.  Here is an example of the discrepancy: a GENMOSAB module (simple start-stop box mosaic) in CASPER will always be performed with fixed scan and step sizes relative to inertial space.  A GENMOSAB module performed by Cassini can be specified relative to, for example, the center of Saturn.  While the scan and step sizes of the mosaic are fixed in inertail space, they take place on top of a tracking turn which tracks Saturn as seen by Cassini.  The actual turns performed by the spacecraft are not fixed, because IVP is tracking the body, whose relative motion is in general non-linear.  In cases where the spacecraft is close to the target body, this will result in CASPER displaying an observation that is very different from that request.  At larger distances, the discrepancy is small.  These inertial modules in CASPER do, however, pass the user's requested module parameters to be saved in a CASPER Output File where they can be used by subsequent ground software packages.  Thus, if a user requests a 2 by 2 mosaic of Titan, CASPER will display a mosaic that does not include the IVP target motion compensation and which will be worse than the observation that Cassini is capable of achieving.  The output from that CASPER module will, however, include the module parameters which can be used to construct a sequence for Cassini that will use IVP and track the target.  The IVP versions of modules in CASPER do simulate the target tracking turn as well as the module parameter turns, and will display the observation as the spacecraft will perform it.  To get an accurate time and pointing profile, however, you must take the CASPER output and run it through PDT which calls KPT, the actual spacecraft kinematic predictor tool.

To design a module in CASPER, either in Target or Skymap, open the Module Selection Widget by clicking on the shortcut button (schematic of 3x2 mosaic) or selecting Modules under the Sequence Design-Mosaic Tools menu.


Mosaic Definitions

Mosaics and Scans

Target Scans Polynomial Scans Radar MAPS