Towards a Gaia accuracy toolTowards a Gaia accuracy tool1. Astrometric accuracy (Gaia-JdB-006 + 008)

• Developed using Fortran-77 modules from LennartLindegren (e.g., NSL, SCAN, PSF, LOCEST)

• Under auspices of (Astrometric) Accuracy WG2. Photometric accuracy

• Aperture photometry planned• Under auspices of Photometry WG

3. Radial velocity accuracy• Cross-correlation planned• Under auspices of RVS WG

AstrometricAstrometric accuracy tool (1)accuracy tool (1)Goals (Gaia-LL-043):Realistic (cf. complete) end-to-end simulation tool …… for “perfect case” (single star, non-variable, no planets, no micro-lensing, uniform sky background, …)Modular (extendable and flexible)Central parameter file (integrity)Batch processing (pipeline)Note:Detailed effects considered separately (e.g., double stars)Some effects entered ad-hoc (e.g., attitude rate errors)Conservative estimates (e.g., worst-case AC motion)

Astrometric accuracy erroranalysis tree (Gaia-LL-043)

AstrometricAstrometric accuracy tool (2)accuracy tool (2)1. Source

Effective spectrum2. Mission

NSL, mission length, dead time, transits/CoI

3. Optics and detectorMirror, vignetting, QE

4. PSFWFE, MTF, AC motion

5. Observe objectLSF, Poisson and RON noise, sky background

6. Windowing/sampling7. LSF centroiding

Monte Carlo8. Calibration (missing)

Basic angle, attitude, chromaticity, geometric

9. End-of-missionDetection probability, focal plane, contingency

10.RepeatSpectrum, extinction, magnitude, (α,δ), sky

Current status Astrometricaccuracy tool (Gaia-JdB-008)

X XX XXX

Towards a Gaia accuracy toolTowards a Gaia accuracy toolGaia Science Team (mid-2003):Exploit advanced status Astrometric accuracy toolExplore commonalities (Galaxy model, scanning law, CCD model, interface with Gaia parameter database, …)Include photometry and radial velocity into single tool

Agreed procedure:WGs assess priorities and provide tools/modulesJdB integrates into central Gaia accuracy toolBoundary condition: structure existing astrometric tool

Radial velocity accuracyRadial velocity accuracy

Remainder of presentation:Personal, non-expert, zeroth-order ideas only …Aimed at opening discussion within RVS WGStrategy to be decided upon by RVS WG (within given boundary conditions)

Radial velocity accuracy tool (1)Radial velocity accuracy tool (1)Goals (RVS-ACC-001):Realistic (cf. complete) end-to-end simulation tool …… for “perfect case” (single star, non-pulsating, no spectrum overlap, uniform sky background, …)Modular (extendable and flexible)Central parameter file (integrity; Gaia parameter database)Batch processing (pipeline)Note:Detailed effects considered separately (e.g., confusion) Some effects entered ad-hoc (e.g., template mismatch)Conservative estimates (e.g., coarse C-C peak fitting)

Error sources that may impact radial velocity accuracy (RVS-ACC-001)

Gaia accuracy toolGaia accuracy toolSchematic diagram for astrometric, photometric, and radial velocity accuracy

Legend:in placeplannedto be developed

Astro Photo Radial

Radial velocity accuracy tool (2)Radial velocity accuracy tool (2)1. Source

Effective spectrum2. Mission

NSL, mission length, dead time, transits

3. Optics and detectorMirror, vignetting, QE

4. Transit spectrumWFE, MTF, AC motion

5. Observe objectPoisson + sampling + RON noise, sky backgr.

6. CCD summation7. Cross-correlation

Background subtraction,wavelength calibration Monte Carlo

8. Calibration (“S-GIS”)Barycentric zero-point

9. End-of-mission10.Repeat

Spectrum, extinction, magnitude, [Fe/H], ro-tation, sky background

Proposal for initial error sources in radial velocity accuracy tool

Some questions for youSome questions for you

Which error sources deserve inclusion initially?Who will provide what and when?

Develop end-to-end tool or start with, e.g., ZEMAX-derived PSF or even transit spectra?Use Fortran-77 exclusively or also use, e.g., ANSI-C modules, IRAF fxcor, …?