Transcript SPENVIS-NG_OG_ESWW2013_-number-2918065

Orbit Generator for the Next
Generation SPENVIS
Ángela Rivera(1), Ignacio Grande(1), Esther Parrilla(1), Noelia Sánchez(1), Daniel Heynderickx (2), Michel Kruglanski(3)
(1) DEIMOS Space S.L.U., Ronda de Poniente 19, 2°2, Tres Cantos, Madrid, 28760 Spain,
Email: [angela.rivera, ignacio.grande, esther.parrilla, noelia.sanchez]@deimos-space.com
(2) DH Consultancy, Bondgenotenlaan 148/0401, B-3000 Leuven, Belgium
Email: [email protected]
(3) Belgian Institute for Space Aeronomy , Ringlaan-3-Avenue Circulaire, B-1180 Brussels, Belgium
Email: [email protected]
INTRODUCTION TO SPENVIS-NG
The Next Generation SPace ENViroment Information System is the latest
revision and update to the current SPENVIS system, a web interface to
models of the space environment and its effects, including the cosmic
rays, natural radiation belts, solar energetic particles, plasmas, gases, and
micro-particles.
One of the core functionalities is the Orbit Generator: a module that reads
the orbit definitions for a mission in a wide range of formats and computes
a common-format orbit ephemeris to be used by the different models
available to SPENVIS users.
CURRENT ORBIT GENERATOR: SAPRE
The current SPENVIS system uses SAPRE as orbit generator.
SAPRE is a powerful and versatile orbit generator that suits SPENVIS
needs, however, it lacks proper documentation and its capabilities exceed
by far SPENVIS-NG requirements of a fast, not-so-accurate propagator.
In addition, input format requirements of SPENVIS-NG would make
necessary to modify SAPRE, a task that would require quite some time to
accomplish.
For these reasons, it has been decided to develop a new, easier to
maintain Orbit Generator, with the required capabilities of input and output
formatting.
NEW ORBIT GENERATOR: DESIGN PRINCIPLES
The design of the Orbit Generator will be based on the following principles:
• Simplicity: provide the simplest possible tool that covers the required
functionality.
• Modularity/Flexibility:
provide
a
solution
that
allows
future
improvements to be added easily, which is something difficult to do
currently in SAPRE.
• Boost development process: trying to understand SAPRE architecture
would probably take more time than implementing the necessary
requirements.
CAPABILITIES
The Orbit Generator fulfils the requirements of the SPENVIS-NG space
environment modules regarding the orbit ephemeris and also the user’s
requirements regarding input file formats, and necessary graphic
representation (actual graphic generation is done by a generic plotting
module).
Some of the capabilities of the Orbit Generator include:
• Segment-based propagation. A project may contain several segments
with different orbit definitions.
• Multiple central bodies, including the Sun, Solar System planets and
their large natural satellites.
• Keplerian propagation. This is a very fast analytical propagator with
reduced accuracy, however, accuracy requirements are generally low for
Space Weather applications, and propagations arcs are short.
• Versatile input formats: Keplerian elements, ESOC Long Term Orbit File
(LTOF), CCSDS OEM format and current SPENVIS output ephemeris
format.
• VOTables format used for ephemeris output.
• Output ephemeris contains a series of state vectors in J2000, coded in
VOTables.
• TLE files can be uploaded from the user or downloaded from Internet
providers (Space-Track, Celestrak, etc.) to be used as input format by
the Orbit Propagator.
10th European Space Weather Week
Solar-Terrestrial Centre of Excellence,
November 2013
Antwerp, Belgium
A mission can be defined by different propagation segments, as the
LEO-GTO-GEO case shown in the figure (not actual SPENVIS output)
ARCHITECTURE
The Orbit Generator will aim for short trajectories divided into segments
instead of in creating the whole orbit of a spacecraft for the duration of the
mission. This will provide a less cumbersome simulation model that will
keep at a minimum the resources consumed by the users in terms of CPU
time and disk space.
A mission contains information about the starting date, mission duration
and a set of segments. Each segment contains the following information:
• Segment start date and duration.
• Trajectory duration, used to compute the actual propagation.
• Central body and orbit information
Independently of the input format of the orbit information, the propagation
will be performed separately for every segment, and the output will
contain the following information in VOTables format:
• Time interval computed.
• Ephemeris information with epoch in MJD UTC and state vector in J2000
coordinates for each ephemeris step.
Both input and output is stored in a predefined directory structure,
compatible with the SPENVIS-NG ecosystem.
SUPPORTING LIBRARIES
Two libraries will be used to support the development of the Orbit
Generator:
• JPL SPICE Tool, a tool already known in other ESA missions (Huygens,
Mars and Venus Express, Rosetta and currently in Ganymede). The tool
provides subroutines to perform Keplerian and SGP4 propagation,
coordinate transformation and state vector interpolation, among others.
• DH Consultancy tool currently used for GREET contract, that uses JPL
SPICE itself to compute state vectors using Ganymede as central body.
Source code of this tool is available and can be modified to suit
SPENVIS-NG needs.
• IRBEM-LIB package will be also used for some Earth-centred coordinate
transformations needed due to the versatile input format supported.
All these libraries are available in Fortran, the chosen language for the
Orbit Generator.
The work presented in this paper is done within ESA/ESTEC Contract No. 4000104812
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