MEX SPK Files
=============
This "aareadme.txt" file describes the contents of the kernels/spk directory
of the MEX SPICE data server. It also provides the file naming conventions
used for the MEX SPK kernels, and it provides identification of the most
current version of each kind of SPK file.
Some of these SPK files are produced by an automated system located
at ESAC, operated by the ESA SPICE Team.
The contents and time span covered by any SPK file may be easily determined
using the "brief" utility program available in all copies of the
SPICE Toolkit. Example of usage:
$ brief <spk_file_name>
Descriptive information about how/why/when an SPK file was created is
usually available in the "comment area" of the file. This may be viewed
using the "commnt" utility program available in all copies of the
SPICE Toolkit. Use the "-r" option to read the comments. Example:
$ commnt -r <spk_file_name>
All binary SPK files (*.BSP) contained in this directory are Unix binary
files. These may be used as is (without format conversion) in a non-unix
environment when using any recent version of the SPICE Toolkit (Version
N0052 or later).
Contact
ESA SPICE Team spice@sciops.esa.int
, or
Alfredo Escalante Lopez aescalante@sciops.esa.int
if you have any questions.
References
==========
1. Data Delivery Interface Document (DDID) Appendix H - FD
products Issue 3.0 (MEX-ESC-IF-5003)
2. SPK Required Reading (NAIF Document).
3. "Astrometric Observations of Phobos and Deimos with the SRC on
Mars Express", Oberst, J. et al. Astronomy and Astrophysics. Accepted
07-Oct-2005
All the NAIF Documents are available at the NAIF web:
http://naif.jpl.nasa.gov
Mars Express SPK Directory Structure
====================================
aareadme.txt This file.
former_versions Subdirectory that contains obsolete
versions of the SPK files that have been
updated in the Current SPK Kernels Set.
C2013A1_S105_MERGED.BSP SPICE Kernel (SPK) that contains ephemeris
data for Comet Siding Spring. Spans the
entire Mars Express mission.
DE405.BSP SPICE Kernel (SPK) that contains ephemeris
data for planet barycenters, and for the
sun, earth and moon mass centers. Spans the
entire Mars Express mission.
EARTHSTNS_ITRF93_YYMMDD.BSP SPICE Kernel (SPK) that contains ephemeris
data for NASA DSN stations relative to the
terrestrial reference frame label 'ITR93'.
This file was released on YY-MM-DD.
ESTRACK_Vvv.BSP SPICE Kernel (SPK) that contains the
position for each of the ESA ESTRACK ground
stations relative to the center of the
Earth. In the interest of flexibility, in
this file the reference frame is labeled
with the alias 'EARTH_FIXED'. Any
application using this file must map the
alias 'EARTH_FIXED' to either 'ITRF93' or
'IAU_EARTH'.
EARTHSTNS_RU_YYYYMMDD.BSP SPICE Kernel (SPK) that contains the
position for each of the Russian ground
stations relative to the center of the
Earth.
MAR097_030101_300101_V0001.BSP
SPICE Kernel (SPK) that contains JPL
ephemeris data for Phobos, Deimos, Mars
and Earth. Spans the entire Mars Express
mission.
MEX_ASPERA_STRUCT_Vvv.BSP SPICE Kernel (SPK) that contains relative
locations of the ASPERA structures with
respect to the spacecraft bus and each
other. This SPK spans the entire Mars
Express mission.
MEX_PFS_ROIS_Vvv.BSP SPICE Kernel (SPK) that contains position
information for Mars Express Regions of
Interest for the PFS instrument.
MEX_RELAY_LOCATIONS_VVV.BSP SPICE Kernel (SPK) that contains position
information for selected landers and rovers
for which Mars Express is a relay for.
MEX_ROB_YYMMDD_yymmdd_vvv.BSP SPICE Kernel (SPK) that contains high
precision ephemeris for Mars Express (MEX),
created by the Royal Observatory of
Belgium. The kernels cover MEX position
from YY-MM-DD to yy-mm-dd; vvv is the
version number.
MEX_STRUCT_Vvv.BSP SPICE Kernel (SPK) that contains the
location of various Mars-Express
instruments and structures.
ORHM_______________xxxxx.BSP SPICE Kernel (SPK) that contains Mars
Express spacecraft reconstructed
cruise ephemeris. This ephemeris
corresponds to the ESOC orbit file named:
ORHM_FDLMMA_DA______________xxxxx.MEX
where xxxxx designates the version number.
ORMF_______________xxxxx.BSP SPICE Kernel (SPK) that contains Mars
Express spacecraft long term planning
operational Mars centric ephemeris. This
file is generated by merging the previous
version of the kernel with the one generated
from the latest ephemeris from the ESOC
orbit file named:
ORMF_FDLMMA_DA______________xxxxx.MEX
ORMF___________T19_xxxxx.BSP SPICE Kernel (SPK) that contains Mars
Express spacecraft long term planning
operational Mars centric ephemeris. This
product is a Type 19 SPK kernel and requires
at least the SPICE Toolkit N0065 to be used.
This file is generated by merging the
previous version of the kernel with the one
generated from the latest ephemeris from the
ESOC orbit file named:
ORMF_FDLMMA_DA______________xxxxx.MEX
where xxxxx designates the version number.
This is the file that should be used for
planning. For data analysis you have to
use the ORMM files below.
ORMF_YYMMDD_yymmdd_xxxxx.BSP SPICE Kernel (SPK) that contains Mars
Express spacecraft long term planning
operational Mars centric ephemeris. This
ephemeris corresponds to the ESOC orbit
file named:
ORMF_FDLMMA_DA______________xxxxx.MEX
where xxxxx designates the version number
and YY-MM-DD yy-mm-dd designate start and
end dates. This is the file that should be
used for planning. For data analysis ORMM
files below should be used.
ORMF_T19_YYMMDD_yymmdd_xxxxx.BSP
SPICE Kernel (SPK) that contains Mars
Express spacecraft long term planning
operational Mars centric ephemeris. This
product is a Type 19 SPK kernel and requires
at least the SPICE Toolkit N0065 to be used.
This ephemeris corresponds to the ESOC orbit
file named:
ORMF_FDLMMA_DA______________xxxxx.MEX
where xxxxx designates the version number
and YY-MM-DD yy-mm-dd designate start and
end dates. This is the file that should be
used for planning. For data analysis ORMM
files below should be used.
ORMC_FD_xxxxxxxxxxxxxxxx.BSP SPICE Kernel (SPK) that contains Mars
Express spacecraft long term operational
Mars centric ephemeris. These files are
used as candidate orbits in order to
analyse different options before
implementing the long term operational
orbit (ORMF).
ORMM__YYMMDDhhmmss_xxxxx.BSP SPICE Kernel (SPK) that contains Mars
Express predicted and reconstructed
ephemeris after orbit insertion, starting
from YY-MM-DD. This ephemeris
corresponds to the ESOC orbit file named:
ORMM_FDLMMA_DA_YYMMDDhhmmss_xxxxx.MEX
where xxxxx designates the version number.
These are the files that should be used
for data analysis.
ORMM_T19_YYMMDDhhmmss_xxxxx.BSP
SPICE Kernel (SPK) that contains Mars
Express predicted and reconstructed
ephemeris after orbit insertion, starting
from YY-MM-DD. This product is a Type 19
SPK kernel and requires at least the SPICE
Toolkit N0065 to be used. This ephemeris
corresponds to the ESOC orbit file named:
ORMM_FDLMMA_DA_YYMMDDhhmmss_xxxxx.MEX
where xxxxx designates the version number.
These are the files that should be used
for data analysis.
Note: Files EARTHSTNS_FX_yymmdd.BSP and EARTHSTNS_ITRF93_yymmdd.BSP contain
the same data. These files only differ in that the second one use the
reference frame label 'ITR93' instead of 'EARTH_FIXED'. 'EARTH_FIXED' alias
must be map to either 'ITR93' or 'IAU_EARTH' before using the file. For high
accuracy work, the EARTHSTNS_ITRF93_yymmdd.BSP is recommended (on the basis
of ease of use).
About Phobos and Deimos ephemeris
=================================
The current Mars Express SPICE data set contains five SPKs giving ephemeris
data for both Phobos and Deimos. Four out of the five files correspond to
the JPL orbit solutions for both Mars' moons, and the third one to the ESOC
orbit solutions.
The official JPL SPK file, provided by NAIF and named MAR033_2000-2025,
was used in the data analysis of HRSC/SRC images [Ref. 4]. In this analysis,
the measured Phobos and Deimos positions have been compared with the JPL
predictions. This comparison has shown that Phobos has advanced by approx.
12 km with respect to the JPL model, while the predicted Phobos positions
in the across-track directions are off by only small amounts (+/- 1 km).
Deimos observations show that this satellite has advanced by approx. 50 km,
and is also off across-track by less than 1 km.
The down-track offsets of 12 km and 50 km of the satellites' position
can be removed by shifting in time the Phobos and Deimos ephemeris. This
solution has been implemented and a new SPK kernel produced:
MAR033_HRSC_V03.BSP
This file solves the down-track offsets but there are still some
across-track inconsistencies that remain, until a new orbit solution, more
accurate, is provided.
The third file, named MARSAT_ESA_040101_V01.BSP, was also used in the
analysis of HRSC/SRC images [Ref. 4]. In this analysis, the measured Phobos
and Deimos positions have been also compared with the ESOC predictions and
the results are the following:
Phobos' predicted position is 2 km ahead of the measured position,
and it is off by +/- 8 km cross-track.
Deimos' predicted position is 5 km ahead of the measured position,
and it is off by +/-18 km cross-track.
A comparison of official the ESOC and JPL orbit solutions of Phobos for
epochs in 1989 show position differences over one Phobos orbital revolution
ranging from 3 km to 7.5 km. These differences are mainly periodic.
At the time frame of the ESOC file, 2004-2006, the same comparisons show
larger differences over a Phobos orbital revolution, ranging from 6km to
22 km.
The fourth file, MAR063.BSP is the official ephemeris from JPL, using MRO
observations. This is the baseline kernel used for planning.
The fifth solution, MAR080.BSP, is a slightly improvement over the previous
one, using Mars Express data.
-------------------
This file was last modified on March 22th, 2021. (R. Valles)
End of aareadme file.