| DATA_SET_DESCRIPTION |
1. SPICE System Overview
=====================
SPICE data contain geometric and other ancillary information
needed to recover the full value of science instrument data. In
particular, SPICE kernels provide spacecraft and planetary
ephemerides, instrument mounting alignments and spacecraft
orientation. Data needed for relevant time conversions is also
included.
SPICE was designed by the Navigation and Ancillary Information
Facility (NAIF) to aid scientists and engineers with ancillary
and engineering data. This data comes from a wide range of
sources such as the spacecraft, the mission control center and
the designers of the spacecraft and its instruments.
The ancillary data comprises information on data acquisition;
position and orientation of the spacecraft at the time of
acquisition; information on the target, such as location, shape
and orientation; reference frame specifications and time
conversion data.
The primary SPICE data sets are often called 'kernels' or 'kernel
files'. These kernels are composed of ancillary information,
which has been created in such a way as to allow easy access and
correct usage by the space science and engineering communities.
In addition to the kernels, there is software provided, known as
the SPICE toolkit, along with standards, documentation and
software support. The SPICE toolkit and documentation can be
found on:
http://naif.jpl.nasa.gov/naif/
The SPICE toolkit was freely offered to the worldwide space
science and space mission engineering communities at the time
this data set was released. The few rules governing its use are
posted on the 'Rules' page of the NAIF website:
http://naif.jpl.nasa.gov/naif/rules.html
SPICE is used on a number of space missions, such as ESA's Mars
Express, SMART-1, Venus Express and Rosetta missions; NASA's Mars
Global Surveyor, Stardust, Cassini, Mars Exploration Rovers, Mars
Reconnaissance Orbiter and Deep Impact. The SPICE system has been
produced and is maintained by Caltech's Jet Propulsion Laboratory
under contract to the U.S. National Aeronautics and Space
Administration.
For an additional explanation of the SPICE system, please consult
SPICE_INST.CAT
2. Data Producers and Other Key Personnel
======================================
The Rosetta SPICE data set has been produced by
Acton, C. (NAIF/JPL)
Bachman, N. (NAIF/JPL)
Semenov, B. (NAIF/JPL)
Vazquez, J.L. (RSSD/ESA)
Zender, J. (RSSD/ESA)
and archived by
Vazquez, J.L. (RSSD/ESA)
3. The Rosetta SPICE dataset
=========================
The Rosetta SPICE dataset consists of several SPICE kernels,
organised as follows:
* CK kernels. This kernels contain information about
orientation of the space vehicle or any articulating
structure on it. More information on the CK kernels in this
dataset is provided in CKINFO.TXT.
* FK kernels. Reference frame specifications. Definitions of,
and specifications of, relationships between reference frames
(coordinate systems). Among the frames kernels included,
there are kernels that specify reference frames related to
the earth and the spacecraft. More information on the FK
kernels in this dataset is provided in FKINFO.TXT.
* IK kernels. Kernels that hold intrument information, such as
field of view or internal timing. There is a IK kernel for
every instrument, except for RSI. More information on the IK
kernels in this dataset is provided in IKINFO.TXT.
* LSK kernel. This kernels hold a table with the leapseconds
used to convert between ET and UTC. If there are multiple
LSK kernels in this dataset, the latest kernel supersedes the
previous ones. More information on the LSK kernel(s) in this
dataset is provided in LSKINFO.TXT.
* PCK kernels. These kernels provide information about Solar
System bodies orientation and shape, and possibly parameters
for gravitational, atmospheric or rings models. The dataset
contains PCK kernels for the planets, their satellites, and
the asteroids Lutetia and Steins. More information on the PCK
kernels in this dataset is provided in PCKINFO.TXT.
* SCLK kernel. This kernel (spacecraft clock coefficients)
allows for conversion between ET and spacecraft clock. If
there are multiple LSK kernels in this dataset, the latest
kernel supersedes the previous ones. More information on the
SCLK kernel(s) in this dataset is provided in SCLKINFO.TXT.
* SPK kernels. Kernels with information about ephemeris
(position and velocity) of the spacecraft and solar
system bodies. The dataset provides such information for
the planets, the Sun, the Moon, the comet
(CHURYUMOV-GERASIMENKO), the two fly-by asteroids
(Lutetia and Steins), the fly-by comet (Tempel 1), the New
Norcia tracking Station, and the spacecraft. More information
on the SPK kernels in this dataset is provided in SPKINFO.TXT.
3.1 - Origin of the kernels.
a) Generic kernels provided by NAIF.
PCK, LSK and some of the SPK (those which don't hold
information about the spacecraft) kernels are provided
by NAIF.
b) Other kernels provided by NAIF.
The instrument kernels (IK) have been developed by Boris
Semenov (NAIF), in collaboration with the intrument teams
and RSSD/ESA.
c) Kernels generated with ESOC Ancillary Data.
ESOC ancillary data are the main source of information
required to create SPICE kernels for attitude (CK), orbit
(SPK) and time (SCLK) information, as well as orientation
for the High Gain Antenna and the Solar Panels. See next
chapter (3.2) for a more detailed explanation on how these
kernels are generated. Some PCK kernels for asteroids and
comets have also been created using ESOC data.
3.2 - Creation of SPK, CK and SCLK kernels from ESOC Ancillary
Data.
Orbit Data.
----------
Eight different types of data products are provided by
ESOC: ORHR, ORHO, ORHS, ORER, ORMR, ORFR, ORGR and ORWR.
SPICE kernels corresponding to ORHR, ORWR, ORHS, ORHW
and ORHO will be provided in this data set.
The ORHR SPK file covers the cruise phase from launch to
the rendezvous with the comet and provides the orbit data
as heliocentric states. There will be several versions of
the ORHR product; the user shall use the file with the
higher version number, since it will be the most up to date
one.
The ORHW SPK file provides orbit data, centered in the
Sun, for the comet Churyumov-Gerasimenko.
The ORHS SPK file provides orbit data, centered on the
Sun, for the asteroid 21 Lutetia.
The ORHO SPK file provides orbit data, centered on the Sun,
for the asteroid 2867 Steins.
During near comet operations, one spacecraft orbit file
(ORHR) will be provided, containing comet-centric states
with respect to the Earth mean equator of J2000. The file
will cover the spacecraft orbit from comet rendezvous up
to the end of the current planning period.
For each release of the dataset, only the relevant kernels
are delivered. For example, for the first release, ORHO and
ORHS files will not be delivered, since that release covers
a time period previous to the two asteroid flybys.
Attitude Data.
-------------
Attitude data are provided for all mission phases except
for safe modes, for the past and the near future. The
attitude is provided in several records, called segments,
each covering a specific time span. These segments have
no overlap, but there may be gaps between the segments,
and even gaps in the segments.
Time Correlation Data.
---------------------
Time Correlation is one of the most critical pieces of
information needed for the use of the SPICE system within
the Rosetta mission. This information allows the conversion
between the Rosetta S/C Clock time and UTC time.
ESOC always provide predicted and reconstituted orbit data,
but only predicted attitude data. These products are the
source of the CK and SPK kernels.
ESOC delivers time correlation data which are the source for
the SCLK kernel.
An automated system, called ADCS (Automatic Data Conversion
System) is responsible for the generation of CK, SPK and SCLK
kernels from the ESOC flight dynamics data. ADCS detects when
a new product was generated or a new time correlation packet
was available, and run a series of processes in order to
create the proper kernels.
ADCS uses the SPICE toolkit in order to fulfill its task. It
runs in a server physically located at ESTEC until December
2007; after that date, the server is located at ESAC.
3.3 - Using the SPICE kernels.
At least a basic knowledge of the SPICE system is needed in
order to use this kernels. The SPICE toolkit provides versions
in Fortran (SPICELIB), C (CSPICE), Matlab (Mice) and IDL (icy),
and the user can choose any one that suits him/her.
The SPICELIB routine FURNSH, CSPICE function furnsh_c, and icy
routine cspice_furnsh load a kernel file into the kernel pool
as shown below.
CALL FURNSH ( 'kernel_name' )
furnsh_c ( 'kernel_name' );
cspice_furnsh, 'kernel_name'
In the case when two or more files contain data overlapping in
time for a given object, for binary kernels, the file loaded
last takes precedence.
If two (or more) text kernels assign value(s) using the '='
operator to identical keywords, the data value(s) associated
with the last loaded occurrence of the keyword are used -all
earlier values have been replaced with the last loaded
value(s).
Loading Kernel Files into a SPICE-based Application
===================================================
The following list of kernels in SPICE meta-kernel format can
be used with a SPICE-based application running on a UNIX
workstation to load Rosetta SPICE data provided in this data
set together (note that the logical path provided in the
PATH_VALUES keyword and pointing to the volume root directory
should be changed to the actual path of the volume root
directory on the system where the volume is mounted):
When there are two or more kernels that cover the same time
interval (as is the case here for the .BSP and .BC kernels)
the last kernel loaded is the one used by the SPICE software
for computations in the interval or overlap.
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