FASR Calibration and Data Management Issues Gordon Hurford Space Sciences Lab University of California, Berkeley 9 Feb 2006 FASR Development Meeting

Calibration – FASR-Specific Science Drivers (1) FASR quantitative science is largely based on spatially- resolved continuum spectroscopy  typically derived from image cubes (spatial/spectral MEM ?)  Closely spaced frequencies  Image fidelity  Relative Photometry, Tb (freq)  Image dynamic range impacts effective spectral range Solar science often involves comparison with other datasets.  Absolute positions to <~1 arcsecond

Calibration – FASR-Specific Science Drivers (2) Observational continuity –Solar features evolve on timescales from seconds to days. –Calibration data gaps highly undesirable Particularly problematic for flare studies (timescales of seconds to 10s of minutes) Calibration data sources Solar signal dominates Tsys Target sources much stronger than calibration sources

Approaches to phase calibration (1) Phase-stable design –BUT tropospheric and ionospheric effects are still problematic Redundant baselines + solar limbs (eg Nobeyama) – not applicable to FASR Frequent phase calibrator observations –Introduces serious data gaps –Minimizing gaps drives sensitivity requirements –A fallback option?

Approaches to phase calibration (2) Solar self-cal –Exploit strength of ‘target’ to provide continuous self-calibration How to determine absolute source position –Tropospheric wedge has only limited impact on imaging spectroscopy. –Absolute positions need be known ‘only’ to ~ 1 arcsec. –Absolute positions defined by 2 tropospheric + 2 ionospheric ‘sky- wedge’ parameters

‘ Sky-wedge’ Calibration Options Subarray-based –Subarray continuously or intermittently monitors calibrators to define skywedge –Dedicated antenna subset with lower noise receivers? Active region continuity Active regions evolve slowly and traverse disk at known rates Can interpolate their true positions between pre-dawn and post- dusk calibrations ?

Calibration Issues Identification of other ‘tall pole’ calibration issues that may drive design New insights into FASR calibration issues? Quantify implications of the conventional calibration option (in progress). Test feasibility/performance of other calibration options (subarray and solar continuity) using archival data or test observations with VLA. –Do either of these options provide a viable basis for FASR phase calibration?

Data Management – Science Drivers Sun is a time-variable, unpredictable object Analysis topics/targets not known in advance ~12-hour not 24-hour observing day Diverse (and interferometrically naïve) user community Typical data products –Light curves at multiple frequencies –Dynamic spectra –Maps at multiple times, frequencies and targets –Spectra at multiple times –Parametric maps (eg magnetic field or coronal density)

Data Management – User Community Space weather community –‘ Real-time’ high-level standardized data products, delivered transparently –No user involvement in analysis Solar community –Quick-look standardized high-level data products to support other studies –High level data products with user-specified parameters to match external datasets –No user user knowledge of interferometry Solar radio community Access to lower level data for custom analyses

X xxx FASR Data Flow

FASR-A 0.1 GB/s 4 TB/day 50 GB/day ~1 GB/day X xxx Simplified Data Pipeline Interim Database Semi-calibrated visibilities, housekeeping data, etc Time and frequency resolution are scientifically uncompromised Transient – designed to be overwritten every hrs. 4 Tbytes / day (FASR-A) (100ms,1%)

FASR-A 0.1 GB/s 4 TB/day 50 GB/day ~1 GB/day X xxx Simplified Data Pipeline Interim  Application Databases Magnetography bursts general purpose etc FREQUENCY TIME

FASR-A 0.1 GB/s 4 TB/day 50 GB/day ~1 GB/day X xxx Application Databases Set of parallel databases for magnetography, bursts, etc Time and frequency resolution tailored to specific applications Fully calibrated Starting point for generation of high level data products ~50 Gbytes / day Simplified Data Pipeline

FASR-A 0.1 GB/s 4 TB/day 50 GB/day ~1 GB/day X xxx Simplified Data Pipeline Interim Database Semi-calibrated visibilities, housekeeping data, etc Time and frequency resolution are scientifically uncompromised Transient – designed to be overwritten every hrs. 4 Tbytes / day (FASR-A) (100ms,1%) 200 Tbytes / day (FASR-B) (10ms,0.1%) 120 Tbytes / day (FASR-C) (10 ms 0.1%)

FASR-A 0.1 GB/s 4 TB/day 50 GB/day ~1 GB/day X xxx Simplified Data Pipeline Interim Database Semi-calibrated visibilities, housekeeping data, etc Time and frequency resolution are scientifically uncompromised Transient – designed to be overwritten every hrs. 4 Tbytes / day (FASR-A) (100ms,1%) 200 Tbytes / day (FASR-B) (10ms,0.1%) 120 Tbytes / day (FASR-C) (10 ms 0.1%) Need careful science justification for time and spectral resolution Need close to real time data selection for FASR B,C

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