SWG & DMS/PS simulations

April 19 2002 DMS/PS-WG meeting 1

GAIA SWG

SWG &

DMS/PS simulations

C. Babusiaux, X. Luri, E. Masana, F. Arenou


GAIA SWGSWG 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


GAIA SWG

Community involvement: task list


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


GAIA SWG

Organisation of the work


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


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


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/

http://www.cvshome.org/




GAIA SWGCommon tool box & data generators


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


GAIA SWG

Status


GAIA SWGThe 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,...)


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.


GAIA SWG

ReferenceUniverse

Snap-shot(t1,t2)

GAIADB

Objects

Background

Scan lawAttitudeEfemerisetc.

InstrumentsNoiseetc.

Data processes:

Reduction & calibrationScientific exploitationetc.

GASS activities

TelemetryRaw data

ApparentSky

Housekeepingdata

Satellite &instrument

model


GAIA SWGGASS - 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).


GAIA SWGGaia 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


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


GAIA SWGGIBIS Status

• DevelopmentUML design, Java core, Iraf Image simulationx Web page

• InstrumentAll instruments, Gaia2, Detection, PSF, Noisex 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


GAIA SWG

Priorities & schedule


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


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!


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)


GAIA SWGSWG priorities – short term (2002-2005) I

• Mission designDetailed testing of the capabilities of the revised GAIA designSimulations to complete Spectro design and evaluate its performanceTelemetry & compression: final budget and trade-offsOn-board data handling design

• Data analysisDatabase design optimisationData processing (pipeline) design

o Ingestion

o Quick-look & initial classification

o Core processing (GIS)

o Spectro & photometry processingQuery system & visualisation tools


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?


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 processingShell processingRefined classification of objectsRefine and expand query system & visualisation tools Interoperability with other large astronomical databases


GAIA SWG

• Scientific exploitationProduce simulated data allowing teams to prepare the exploitation of

GAIA data (through GAIA DB?).

SWG priorities – long term (2005 ) II


GAIA SWGSWG initial schedule & milestones

• Immediate coordination activitiesComplete task list with names: April 2002Ref. document: May 2002

including schedule for 2002-2005 activities related to mission designincluding schedule for 2002-2005 activities related to mission designComplete the merging of GIBIS & GASS: June 2002

• Integration activities Initial version of web page access to simulations: May 2002Agreed schema for integration of contributions: ??1st version of common tool box: ??Programming interface: ??


GAIA SWG

DMS/PS simulations


GAIA SWGObject 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 MethodAstroObject Single Star

Multiple StarNEOQuasar ...

getPosition(time)

An unique Method with different implementations (one for object type)


GAIA SWGObject 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.


GAIA SWGCrude 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)


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


GAIA SWGII) Observations

•Spectroscopy– Radial velocity

•Photometry (if eclipsing)– Light curve– Light-time travel

R 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


GAIA SWGOptimisations Needed

• More realistic distribution of DMS/PS/BD• Evolved companions• Peculiar objects (contact binaries)• Variable companions


GAIA SWG


GAIA SWG

Backup slides


GAIA SWGInstrument models


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


GAIA SWGThe 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


GAIA SWGJava

• Object-oriented • Really portable • Allows a fast development

• Not too fast • Not yet popular in the astronomical

community• No numerical libraries available


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


GAIA SWGCVS


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.


GAIA SWG

CVS REPOSITORYReference version

of source files

CVS server

CVS client CVS client CVS clientCVS client

Local version

Local version

Local version

Local version

SWG & DMS/PS simulations

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