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edit Master text styles Atacama Large Millimeter/submillimeter Array Karl G.

1 Correlator DataMaster Processor Click to edit title Click to edit Master subtitle style style Click to edit Master text Rodrigo Améstica Click to edit Master text styles Atacama Large Millimeter/submillimeter Array Karl G. Jansky Very Large Array Robert C. Byrd Green Bank Telescope Very Long Baseline Array

2 Outline Cluster overview Data acquisition: hardware interface, data content and handling in software, lags normalization. Data processing: on-line calibration and transformation from normalized correlator lags to auto-correlations and visibilities. Data delivery: data collecting from nodes and formatting into a binary data format suitable for storage. ALMA Correlator Workshop, May,

4 CDP Application Deployment

5 Data Acquisition

6 Data Port Interface

7 Hardware Time Stamp to Absolute time

8 From DMA to Application Memory

9 Lag Processing Overview

10 Data Processing

11 Raw Lags from the Correlator Correlator Multiplication table and accumulation 2-bit sampling per antenna Voltage Binary Weight Analog v l v Gsp 0 v <v l v l v < v v l bit 4 Gsp TDM 20 log 10 ( ) L(τ) raw correlation function 250 MiLags/sec 250 MiLags/sec bias implies Vs db bit integers 32-bit CDP 32-bit floats 8e6 visibilities/sec BDF blobs within ASDM

12 Data Processing Stages

13 2x2-bit Quantization Correction 1 po l σ 1, σ 2 ρ(τ) Vl ec k yn om ia l correlation function ρ Va n R4 (τ) correlation coefficient rms / volt 0 requires signal level for each one antenna in a base-line ρ4

14 Options to Access Total Power On-line Correlator (0) current TDM lag zero available on every correlator dump. (0) or (1) CDP (1) 3-bit population counts added to dumps' meta-data. It would imply just 8 additional integer values per antenna. CAN bus Ethernet (2) (3) IFProc (4) DTX CCC DTX: digital transmitter IFProc: intermediate frequency processor (2) CCC retrieves population counts through specific CAN bus protocol and forwards to CDP (-1683) (3) & (4) devices such IFProc (full fledged square law detector) or DTX could either publish already computed total power figures or population counts, respectively.

15 Spectral Normalization

16 Residual Delay Correction

17 Atmospheric Path Length Correction

18 Data Delivery

19 Incremental Binary Data Formatting

20 Flagging and Blanking Bit Name Reason Implies blanking 0 INTEGRATION_FULLY_BLANKED Empty integration Yes 1 WVR_APC WVR coefficients not received. Yes 2 CORRELATOR_MISSING_STATUS Correlator status not received. Maybe 3 MISSING_ANTENNA_EVENT Antenna delay event was not received. Yes 5 DELAY_CORRECTION_NOT_APPLIED Residual delay correction was not applied. Yes 6 SYNCRONIZATION_ERROR CDP node(s) not properly synchronized N/A 8 TFB_SCALING_FACTOR_NOT_RETRIEVED TFB scaling factor not available. No 9 ZERO_LAG_NOT_RECEIVED Cross CDP node has no auto data. No 12 QC_FAILED Quantization correction failed. No 13 NOISY_TDM_CHANNELS First TDM channels clipped in software. No 14 SPECTRAL_NORMALIZATION_FAILED Cross-correlation not normalized. No 31 ALL_PURPOSE_ERROR Used for troubleshooting purposes. Maybe (*) Not used at this moment (*) To become obsolete Flagging or blanking an integration product is described by additional binary attachments within a BDF sub-header: Flagging implies a flags binary attachment. Blanking implies actual times and actual durations attachments. Flagging and blanking can happen at the same time.

21 Computation and Data Transport Overheads

22 BDF Processing Overview

23 Future Correlator Modes 3-bit, 4-bit quantization modes and double Nyquist sampling to improve sensitivity. A 2-bit correlator provides 88% efficiency, a 3-bit correlator has 96% efficiency, and a 4-bit correlator 99% efficiency. Low complexity. CCC to deduce parameters for already existing protocol. CDP to implement already documented algorithms. 1 software release. Fast accumulation mode. 1 ms correlator dumps in autocorrelation mode only. Low complexity. Already implemented, revive after so much unrelated changes. 1 software release MHz bandwidth modes (highest spectral resolution). Low complexity. CCC to deduce parameters for already existing protocol. CDP to extend frequency-to-channel index mapping. 1 software release.

24 Future Correlator Modes cont'd Side-band separation based on LO1 and TFB frequency offsetting, such that some sub-bands are assigned USB and others LSB, simultaneously. ALMA Use of LO Offsetting for Spurious Signal Suppression and Sideband R ejection Medium complexity. CCC and CDP need to agree how to assign TFB subbands. No new protocols required. 2 software releases. Tsys in FDM mode to allow for more accurate weighting of atmospheric features. High complexity. Sub-tasks in require some attention from CCC and CDP. Never used before protocols. 3 software releases.

25 Future Correlator Modes cont'd Multi-resolution modes to allow for a zoom-in like feature per base-band. Better bandwidth utilization by allowing to observe at two different spectral resolutions within the same base-band. High complexity. There will be some iterations to fully understand the protocol to configure different fractional modes. 3 software releases.

The Correlator Control Computer

The Correlator Control Computer J Perez Atacama Large Millimeter/submillimeter Array Karl G. Jansky Very Large Array Robert C. Byrd Green Bank Telescope Very Long Baseline Array ICT CCC Functional Overview