Corot Instrument Characterization based on in-flight collected data

1. Corot Instrument Characterizationbased on in-flight collected data Leonardo Pinheiro da Silva Corot-Brazil Workshop October 31, 2004 Corot-Brazil Workshop – October 31, 2004

2. Introduction • Some instrument components are susceptible to physical phenomena leading to undesired effects on the scientific data • some might be corrected through modeling, with basis on correlated collected data (e.g. HK data) • others are expected to be negligible, given the defined specifications for the photometric signal Corot-Brazil Workshop – October 31, 2004

3. Objectives • Though the analysis and characterization of some critical aspects we intend to: • validate the theoretical models to be used on ground-based corrections • evaluate the respective modeling parameters • verify the hypothesis enabling some of the noise sources to be neglected Corot-Brazil Workshop – October 31, 2004

4. Some Aspects of Interest • Bias Level (Temp. of Analogic Comp.) • - Electronics’ Gain (Aging) - PSF (Temp. of the Lenses) instrument optics CCD detectors readout electronics digital processing - Spontaneous Generation of e-(CCD Temp.) - Pixel Response Non-Uniformity (+Attitude Jitter) - p+ Impacts (Geo. Position, Effective Shielding) ... Corot-Brazil Workshop – October 31, 2004

5. I. CCDs: Classic Characterization • Reduction of in-flight calibration data to provide: • Dark Fields • Bright pixels map • Dark current law as f(T) • Flat Fields • Black pixels map • Local PRNU statistics Corot-Brazil Workshop – October 31, 2004

6. CCDs: p+ Flux at the Focal Plane • CCDs are susceptible to radiation which depends: • on the satellite position in orbit • on the effective shielding • Effect on the photometry will depend on: • the energy of incoming impacts (generated e-) • the impacted area of the CCD (disturbed pixels) • Specific tools to characterize: • incoming impacts as a function of satellite coordinates • impact effects on the CCD (energy and scale statistics) Corot-Brazil Workshop – October 31, 2004

7. (…) (…) CCDs: p+ Flux at the Focal Plane • Set of images + satellite orbit data => p+ flux (lat, lon) [p+/cm2/s] (lat,lon) Corot-Brazil Workshop – October 31, 2004

8. II. Optics: Spread Function • Collected star light is spread over a region of the detector’s surface • distribution profile depends on stellar magnitude and type, position in the field of view, lenses’ temperature, .. • Knowledge about the spread function is useful in jitter corrections and star coordinates evaluation • Specific tools to estimate: • high-resolution (sub-pixel) spread functions, given a set of images and corresponding satellite attitude data Corot-Brazil Workshop – October 31, 2004

9. Spread Function: Sampled Data projected image acquired data spline interpolation Corot-Brazil Workshop – October 31, 2004

10. ? Spread Function: Data Acquisition attitude jitter spatial sampling (m=6; T=6000K) restituted image Corot-Brazil Workshop – October 31, 2004

11. Spread Function: Restitution projected image typical sample restituted image Corot-Brazil Workshop – October 31, 2004

12. III. Readout Electronics • Signal conditioning is done between the CCD outputs and A/D conversion • Signal is amplified, an offset is imposed • Components are sensitive to thermal fluctuations and aging • Specific tools to characterize the behavior of: • the offset level • the electronic gain • the readout noise Corot-Brazil Workshop – October 31, 2004

13. Example: Electronic Bias • Correlation to T probes, thermal sensitivity, temporal evolution, spectra, .. Astero 1L Exo 1L Astero 2L Exo 2L Corot-Brazil Workshop – October 31, 2004

14. Conclusion • Data processing algorithms have been developed with basis on available in-flight data and calibration requirements • The set of algorithms has been integrated in a mock-up and will soon be migrated to an operational structure • Further work is to be done on other instrument aspects which might also be interesting to characterize... Corot-Brazil Workshop – October 31, 2004