RVS First Look (WP6200)

J.-M. Désert, G. Hébrard , A. Lecavelier, R. Ferlet, A. Vidal-Madjar

Institut d’astrophysique de Paris (IAP)

Workshop RVS CalibrationIAP-November 24th, 2005

Plan

1. GAIA First Look2. Overall RVS First Look3. Details of each RVS First Look steps

Calibration: pixel level

Structure of the coordination unit “C6 Spectroscopic reduction” in the framework of the Gaia Data Processing Consortium.

(Katz et al. « SPE-CU-001 »)

GAIA First LookProblematic

Problems: - Fast monitoring of the GAIA spacecraft - Check the raw telemetry dataflow as soon as it is downloaded- An instantaneous first quick calibration is required- Self calibrating instrument. However, GIS possible only after 6 months.- First analyses of data quality and consistency is required in a daily basis

Solution:

First Look, else risk of losing many months of data and mission time.

Method: Monitoring of the satellite health and the data quality

Remark for RVS:

Advantage: numerous a priori calibration objects exist in the sky

What?– Instrumental follow up– Data sanity check– Quick calibration/analyses

GAIA First Look

Why?– Quick reaction to a problem on the satellite/data chain– Technical diagnostics and alerts– Data diagnostics and alerts

Who?– Ground Segment (GS)– Data Processing Center (DPC)Data Analysis Consortium (=> Coordination Unit DU1000)

How?– Different level of processing at different time executed under different responsabilities– Ground Algorithms applied on onboard processed data (RAW) – Close relations between the 3 instruments

• Time:– Real time– Within ~24 hours

• Diagnostics: – Technical data: instruments (and bus?) control– Scientific data: sanity check and first spectral calibration

• Responsability:– Who makes diagnostics– Who reacts

GAIA First LookDifferent FL tasks

Overall RVS First Look

Quick Look Science Quick Look Detailed First Look

Initial Data TreatmentInput Pipeline

Raw Telemetry

Satellite

Diagnostics: Instrument data Scientific dataResponsability: GS DPC

Time: Real time ~24h

Further data reduction

Input PipelineInput: telemetry stream from Gaia. Output: image-type data

Input PipelineGaia-RVS Ground Processing (RVS-MSC-004)

M. Cropper, D.Katz

First On Ground processing steps

• Stripping of telemetry packaging• Data reformatting • Adding time information • Adding spacecraft coarse attitude• Adding instrument parameters and housekeeping data • Automated Quick Look analysis • Adding starmapper data • Retrieval of relevant astrometric data from Astro database • Ingestion into image products database (IPD)• Science Quick Look

Overall RVS First Look

Quick Look Science Quick Look Detailed First Look

Initial Data TreatmentInput Pipeline

Raw Telemetry

Satellite

Diagnostics: Instrument data Scientific dataResponsability: GS DPC

Time: Real time ~24h

Further data reduction

IDTFirst part of the scientic data reduction chain performed

• Data ingestion• Cross Matching• Generation of elementary data

QLAll GS activities concerning satellite health (i.e. bus and instrument). Uses telemetry stream from GAIA (housekeeping (HK), attitude control system (ACS) data, etc…)

ScQLAll activities concerning scientific data health.Simple and not precise to safe observation time.Generates telecommanding or alerts the scientific.

DFLIn-depth scientific assessment of the quality of the Gaia observations About 24 hours after telemetry reception at the DPC. Produce diagnostics of the status of the satellite and instrument in a more sophisticated manner than can be performed within QL and ScQL.

QL, ScQL & DFL in more details…

QL: Telescope and Instrument follow up

1. Basic telescope informations– Effective area– Optic path– Telescope reflective index

2. Instrument monitoringControl of the instrumental stability:– Thermal – Mechanical– Optical– Global efficiency– PSF / Filter PSF– Wavelength contamination (Blue / Red)

RVS => 100-150 106 sources at ~93 epoch.• Subset of sources which will be bright and stable (astrometrically, photometrically and spectros). • These sources will be monitored daily all along the mission.• Use to self-calibrate the RVS

Trace the evolution of the characteristics of the instrument.

ScQL : data sanity check

• Analyses of the onboard processing outflow parameters

• Long and short term effects– Compare with outflow parameters of the previous day– Compare with outflow parameters of the previous month

• Check the quality of some scientific parameters on a subset of stars– Tests on ribbon of data (bias, bkckgd,etc …)– Xmatch – Quick calibration ->

ScQL : From Ribbons to spectra• Radial velocity (V < 16-17):

– principles: • slitless spectroscopy using Ca triplet (848-874 nm)

– applications:• third component of space motion, perspective acceleration• dynamics, population studies, binaries• spectra: chemistry, rotation

Examples of single transit RVS-like spectra of an F5V star for the apparent magnitudes: V=8, V=10, V=12 and V=14.

GEPI/GAIA-RVS/TN/017.01, F. Crifo, D. Katz

Calibrate detector image Quick spectral extraction

• Extract standard star spectrum ~ 2000°2/day ~ 1/20 of ~2000 Standard Stars

• Background Sky background + Zodiacal Background flux + Diffused light +

Instrumental noise (Readout…) )• Crowding, star densities and faint stars• Wavelength and flux calibrations

=> Quick Diagnostics (Rv)

QL & ScQL : Raw telemetry Product types

The On-board Processing processing tasks in sequence are as follows:

1. CCD gain correction2. Blemish reduction (Fabrication or radiation) 3. Scan law and Across Scan optical distortion correction4. Along Scan optical distortion correction5. Cosmic ray removal6. Co-adding (Pixels? / Over 10 CCDs??)7. Output data selection (Selected pixel on the detector using starmapper)8. Lossless compression

(Cropper et al. « RVS: Technical issues  »)

QL & ScQL need to analyse the result of these steps

DFL : higher level of diagnostics and calibrations

• All the target or Subsets ( Vlimit)• Extract physical parameters

– Extract RV (~1 km/s)– Stellar + interstellar parameters– Early science processing steps - Core processing

• Use all scientific data to assess data and instrument health– Quick Extraction of all physical parameters on all data (?)– Combine spectra from several scans.– Various levels of combined spectra, and derived parameters may exist,

depending on the stage of the mission.

• Feed back with science alerts and object processing

Detailed First Look

Initial Data Treatment

Input Pipeline

Raw Telemetry

Satellite

Calibration Pipeline (SGIS)

Single transit pipeline

Multiple transit pipeline

FL needed for the SGIS Especially at the beginning of the telescope lifetime and in between two nominal calibrations

?

DFL : higher level of diagnostics and calibrations

Gaia-RVS Ground Processing (RVS-MSC-004)

M. Cropper, D.Katz

A. Guerrier

Need to doQuantify: what? why? who? how?

- Define which questions should be answered by the RVS-FL - Explicit relations with other instrument FL? (Heidelberg 2 Dec 2005)

Define RVS FL in the GAIA FL framework? I/O flux in between FL of the 3 Instruments:

-Astrometry => Attitude-Sky Mapper => Xmatch With Photometry and RVS

- Define and quantify QL, ScQL and DFL I/O flux, routines and diagnostic parameters.- Quantify real time and subsets? Subsets for QL, SCQL and DFL?- Give a list of a priori calibrator- Auxilliary data? (same as the pipelines?)- Clarify who is in charge of the dvpt of QL, ScQL and DFL?

To be continued…