CASPER can save all relevant basic geometric and
attitude information to an ASCII file. This option
is found under the Target tool file menu as Save
CASPER Output....
The CASPER output file consists of two portions:
a header section at the top of the file that contains
information which is constant for the entire
file, and an attitude section which contains the pointing
information for each footprint or false footprint
in the designed observations.
Most of the information in this section is in
the format of KEYWORD = VALUE, in addition to some
plain English text. The preamble contains
some plain English text identifying the file as a CASPER
output file. Following that is the time
of file creation, the name of the user creating the file, the version
of CASPER, a user-entered file descriptor (one
line), and the operating system of the computer. Next
is information on the CASPER session.
This information holds for all pointing times given in the
attitude section of the file. The inertial
coordinate sytem is given, along with NAIF ID codes for the
spacecraft and target body. The target
body in CASPER is equivalent to the Primary Inertial Vector.
Next is a list of SPICE kernels used by
CASPER in the session.
The final part of the header section is a list
of CASPER module parameters. These parameters do not
necessarily correspond directly to spacecraft
module parameters because CASPER does most calculations
in inertial space, and does not remove target
body motion. That is, CASPER does not model or simulate
Cassini's IVP capability. The first piece
of information is the number of different modules that have
pointing information saved in this file (NUMMODS).
Following that is a series of KEYWORD =
VALUE module parameters. The first set
are user-specified values for articulation of Cassini's
articulating instruments MIMI, CDA, and CAPS.
Unlike the other module values in this file, these
are saved for the last module only.
All parameter keywords have the format MOD#XXX where
# is the number of the module in the file, and
XXX is the module parameter. CASPER begins
counting at 0, so if only one module was created
when the file was saved, all parameters will begin
MOD0. Keywords for additional modules,
if any, would begin MOD1, MOD2, etc. XXX is the CASPER
abbreviation for the module parameter.
For all module parameters, if a user value was not specified,
the default values are used. Not all module
parameters are used for every module, so some information
is superfluous. The module parameters are
defined here.
This section contains spacecraft attitude for
each footprint or false footprint in the modules, and the
spacecraft state vector (position and velocity)
relative to the target body (specified in the header
section) in the inertial coordinate system(also
specified in the target body). For each entry, the time
is given in ET (ephemeris time - seconds
past J2000) and UTC calendar date format. This is followed
by the quaternion which uniquely specifies spacecraft
pointing and attitude, the state vector giving
position (km) and velocity (km/s) of the spacecraft
relative to the target body, and finally the index
number of the module (0, 1, 2, ...) that the
pointing information belongs to.