April 19 2002 DMS/PS-WG meeting 1
GAIA SWG
SWG &
DMS/PS simulations
C. Babusiaux, X. Luri, E. Masana, F. Arenou
April 19 2002 DMS/PS-WG meeting 2
GAIA SWG
SWG Kick-Off meeting – Cambridge 11-12 March 2002
• Involve the GAIA community in the activities of the SWG
• Organise the work and set up a coordination strategy
• Define priorities and needs for simulations
• Define a schedule for simulation activities
GOALS
April 19 2002 DMS/PS-WG meeting 4
GAIA SWG
WP 2000 Common tools
Priority
WP 2100 Universe Models
WP 2110 Solar System D. Hestroffer / F. Mignard
WP 2111 Ephemeris 4
WP 2112 Minor Bodies 2
WP 2120 Galactic objects
WP 2121 Field stars F. Figueras / M. Haywood / A. Robin +
WP 2122 Multiple stars F. Arenou / S. Soderhjelm +
WP 2123 Variable stars F. Figueras +
WP 2124 Peculiar stars 3
WP 2125 Extrasolar planets M. Lattanzi 3
WP 2126 Microlensing W. Evans / V. Belokurov 2
WP 2127 Stellar clusters 2
WP 2128 Diffuse objects 3
WP 2129 Reddening model R. Drimmel 3
WP 2130 Extragalactic objects
WP 2131 Resolved galaxies 2
WP 2132 Unresolved galaxies 1
WP 2133 Quasars 3
WP 2134 Supernovae W. Evans / V. Beloku rov 2
WP 2140 Relativistic model A. Vecchiato 3
April 19 2002 DMS/PS-WG meeting 6
GAIA SWGProposed structure of GAIA simulator
Common toolbox
GASS GIBISPixel-level simulations
Telemetry simulations
Cater for the “official” mission simulation needs
• Mission design (2002-2005)• Preparation of data reduction (2002 )• Preparation of scientific exploitation (2002 )
Specific simulations for scientific purposes
April 19 2002 DMS/PS-WG meeting 7
GAIA SWGProposed organisation of development
CORE TEAM
• Coordination• Maintenance & development of
common toolbox• Ensure that mission needs are
covered
GIBIS TEAM
• Simulated images
GASS TEAM
• Simulated Telemetry
Specific simulations
April 19 2002 DMS/PS-WG meeting 8
GAIA SWGWorking tools
• UML (Unified Modelling Language)Design tool to build software systems
• JavaObject oriented, portable language
• CVS (Concurrent Versions System)Development tool for maintenance of source codeSee http://www.cvshome.org/
April 19 2002 DMS/PS-WG meeting 10
GAIA SWGIntegration of contributions
• Contributions provided by the community
• Integration into the system is a responsibility of the Core Team
• A programming interface, conventions & procedures will be developed
• Documentation should be provided/developed in parallel with the code
April 19 2002 DMS/PS-WG meeting 12
GAIA SWG
The GAIA System Simulator (GASS)
The aim of the GASS is to simulate GAIA telemetry (observation + satellite HK data) using models of the objects and instruments.
The GASS will provide realistic data for:
• Predictions to be used for mission design.
• Filling of test databases (e.g. the GDAAS database)
• Testing of algorithms (e.g. cross-matching, telemetry compression,..) and reduction software (e.g. core processing).
• Evaluation of mission performances, in particular for some peculiar objects (binary stars, NEO’s, extrasolar planets,...)
April 19 2002 DMS/PS-WG meeting 13
GAIA SWG
GASS - Simulation Process
• Simulation of the objects visible along the scan of the instruments. For each object and epoch the program simulates position, kinematics and photometry. This step includes an Universe model and the scanning law and orbitals parameters of the satellite.
• Transformation from sky coordinates to instrument coordinates. This step includes the geometry and the optics of the instrument, together with the configuration of the field of view (FOV).
• Simulation of the observational process according to the instrumental parameters: detection, acquisition of data and telemetry. This step includes a model of the observational process.
April 19 2002 DMS/PS-WG meeting 14
GAIA SWG
ReferenceUniverse
Snap-shot(t1,t2)
GAIA
DB
Objects
Background
Scan lawAttitudeEfemerisetc.
InstrumentsNoiseetc.
Data processes:
Reduction & calibrationScientific exploitationetc.
GASS activities
TelemetryRaw data
ApparentSky
Housekeepingdata
Satellite &instrument
model
April 19 2002 DMS/PS-WG meeting 15
GAIA SWG
GASS - Current status• Reference Universe:
• Sun & Earth: the simulator implements a very simple algorithm to calculate ephemeris for the Sun and Earth. No other solar system bodies are yet considered.
• Galaxy: the Galaxy model from Torra et al. (1999; Baltic Astronomy 8, 171) is implemented. Only main sequence stars (single and binary) are included.
• Satellite model:• Attitude model: nominal scan law (L.Lindegren) and (simplified) satellite orbit
implemented.• Geometric model of the Astro Focal Plane.
• Instrument model:• Only Astro1 and Astro2 instruments are considered.• A simple detection process is simulated in order to obtain the detection
parameters for each object.• A bi-dimensional realistic PSF has been implemented (but does not include
chromaticity or focal plane position effects).
April 19 2002 DMS/PS-WG meeting 16
GAIA SWG
Gaia Image and Basic Instrument Simulator
• Test the on-board algorithms• Detection, Confirmation, Selection• Compression
• Provide statistical results for GASS• Focal plane optimisation studies
• Patches and samples• Impact of CCD degradataion on final accuracy
• Reduction studies• Image combining• Calibration
April 19 2002 DMS/PS-WG meeting 17
GAIA SWGGIBIS Simulator
• Sources• All : ponctual, extended, fast moving objects• Statistical models• Special configurations• Time variation (variability, astrometry)• Observed images (HST)
• Instrument• All transits (scanning law)• All fields• On-board detection, selection, tracking• CCD details (noise,CTI, degradation…)
• Modular & easy to use
April 19 2002 DMS/PS-WG meeting 18
GAIA SWGGIBIS Status
• DevelopmentUML design, Java core, Iraf Image simulation
x Web page
• InstrumentAll instruments, Gaia2, Detection, PSF, Noise
x Scanning law, photometry, selection, tracking, saturation, linearity, CTE, aging, RVS
• UniverseSingle, multiple stars, clusters, galaxies, HST image
x Time variation, cosmic-rays, solar-system objects
April 19 2002 DMS/PS-WG meeting 20
GAIA SWG
2001 2002 2003 2004
Use of simulations for mission/instrument
design
GAIA design is frozen
Short term mission schedule
Use of simulations for data analysis preparationGDAAS
2005
Technology development
April 19 2002 DMS/PS-WG meeting 21
GAIA SWGLong term mission schedule
2005 2010 2015 2020
Use of simulations for data analysis preparation
Launch! Observations
Use of simulations for scientific exploitation preparation
Analysis
Design, build, test
Catalogue!
April 19 2002 DMS/PS-WG meeting 22
GAIA SWGSWG priorities – immediate (2-3 months)
• Set up the Core Team: members! You are invited to join
• Estimate manpower available and match it to needs/deadlines
• Coordination
Packages & tasks, responsabilities
Reference document to organise work
Compilation of conventions, constants & reference terms
(use/complement GAIA-BCN-0??)
• Merging of GIBIS-GASS
• Take into account the new design of GAIA
• Provide acces to simulated data (web page?)
Lists of objects
Images
Telemetry files
GDAAS access (feasibility? DAWG)
April 19 2002 DMS/PS-WG meeting 23
GAIA SWGSWG priorities – short term (2002-2005) I
• Mission design
Detailed testing of the capabilities of the revised GAIA design
Simulations to complete Spectro design and evaluate its performance
Telemetry & compression: final budget and trade-offs
On-board data handling design
• Data analysis
Database design optimisation
Data processing (pipeline) design
o Ingestion
o Quick-look & initial classification
o Core processing (GIS)
o Spectro & photometry processing
Query system & visualisation tools
April 19 2002 DMS/PS-WG meeting 24
GAIA SWGSWG priorities – short term (2002-2005) II
• Scientific exploitationEstimation of GAIA performance for critical types of objects
Simulations for the development of specific algorithms for data reduction.
Other scientific aspects?
April 19 2002 DMS/PS-WG meeting 25
GAIA SWGSWG priorities – long term (2005 ) I
• Data analysisData processing (pipeline) development & optimisation
o Ingestion
o Quick-look & initial classification
o Core processing (GIS)
o Spectro & photometry processing
Shell processing
Refined classification of objects
Refine and expand query system & visualisation tools
Interoperability with other large astronomical databases
April 19 2002 DMS/PS-WG meeting 26
GAIA SWG
• Scientific exploitationProduce simulated data allowing teams to prepare the exploitation of
GAIA data (through GAIA DB?).
SWG priorities – long term (2005 ) II
April 19 2002 DMS/PS-WG meeting 27
GAIA SWGSWG initial schedule & milestones
• Immediate coordination activitiesComplete task list with names: April 2002
Ref. document: May 2002
including schedule for 2002-2005 activities related to mission designincluding schedule for 2002-2005 activities related to mission design
Complete the merging of GIBIS & GASS: June 2002
• Integration activities Initial version of web page access to simulations: May 2002
Agreed schema for integration of contributions: ??
1st version of common tool box: ??
Programming interface: ??
April 19 2002 DMS/PS-WG meeting 29
GAIA SWG
Object simulation: unification of the process
•The AstroObjects that form the ObservingList contain all the methods needed to generate observations. This allows the unification of the process even for very different types of objects.
Class Extended Class Method
AstroObject Single Star
Multiple Star
NEO
Quasar ...
getPosition(time)
An unique Method with different implementations (one for object type)
April 19 2002 DMS/PS-WG meeting 30
GAIA SWG
Object simulation: SnapShots
• The simulation of objects is carried out through the SnapShots.
• A SnapShot is a list of candidate objects (of one or more types) to be observed by an instrument between two times (time1 and time2).
• Example: the SnapShot for the galaxy model is formed by the objects (single stars, binary stars,...) generated into the HTM triangles crossed by the FOV between time1 and time2.
April 19 2002 DMS/PS-WG meeting 31
GAIA SWG
Crude simulation of Double Star / Planets
• Why ?– Initially, to complexify the sky model in GDASS
– Now included in GASS/GIBIS
– Need to be complexified: to be used as a template
• Two Java classes– Generation (dms_simu)
– Use (dms_orbit)
April 19 2002 DMS/PS-WG meeting 32
GAIA SWGI) Generation
• A call each time a star is created
• Randomly choose– Number of companions
– Masses, down to EP
– Orbital elements
• Just needs as input:– The absolute magnitude of the primary
– Optionally colour and mass of primary
• Simplistic assumptions– Mostly based on Duquesnoy&Mayor 1991 for all stars
– Main-sequence assumed
– … needs something more realistic at a later stage
April 19 2002 DMS/PS-WG meeting 33
GAIA SWGII) Observations
•Spectroscopy
– Radial velocity
•Photometry (if eclipsing)
– Light curve
– Light-time travelR CMa, eclipsing binary with a P=100yr companion
•Computes the orbital effect at the given epoch– getPosition(t)
•Simplistic hypothesis– No interaction between companions– No limb darkening, no mass transfer, etc…
•Astrometry
– Alpha, delta
– Distance
April 19 2002 DMS/PS-WG meeting 34
GAIA SWG
Optimisations Needed
• More realistic distribution of DMS/PS/BD• Evolved companions• Peculiar objects (contact binaries)• Variable companions
April 19 2002 DMS/PS-WG meeting 38
GAIA SWGUML
The design and building of the GAIA simulator is a challenging task:
• Need for requirements & specifications to guide the development
• Many teams involved
• Management and coordination required
• Need to organise & control the source code
• Standarisation of tools, methods and interfaces is key for success
April 19 2002 DMS/PS-WG meeting 39
GAIA SWG
The Unified Modelling Language (UML) was developed as a tool for the design and management of software projects:
• Allows to specify, visualize and document a system under development
• Facilitates the collaboration between teams
• Allows a modular, iterative and incremental development
• Provides a common description tool, avoiding ambiguities in the design of the system
April 19 2002 DMS/PS-WG meeting 40
GAIA SWGJava
• Object-oriented • Really portable • Allows a fast development
• Not too fast • Not yet popular in the astronomical
community• No numerical libraries available
April 19 2002 DMS/PS-WG meeting 41
GAIA SWG
We propose to build the system around a Java core.
It is possible, with proper planning, to integrate algorithms & modules written in any programming language.
However, this integration should be carefully planned and carried on to ensure portability and to avoid a heavy load on the team in charge of the integration.
Programming languages
April 19 2002 DMS/PS-WG meeting 42
GAIA SWGCVS
http://www.cvshome.org/
CVS is a version control system used to record the history of the project source files
It allows a team of developers to simultaneously work in the same set of source code files while avoiding the overwritting or incompatibility of each other updates. CVS solves this problem by insulating the different developers from each other. Every developer works in his own directory, and CVS merges the work when each developer is done.
At the same time, it ensures that each developer has the most recent version of the files.
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