IF processor and Spectrometer Laboratory Test Setup CIT IF processor 8 channel prototype Digital FFT spectrometer

Supercam IF processing consists of basic analog filtering, down-conversion, amplification, and total power measurement.

Half of Supercam Spectrometer in narrow band mode (16 IF's, 500 MHz each, 2048 channels) IF bandpasses Injected tones

Half of Supercam Spectrometer, in wide-band mode (8 IF's, 1 GHz each, 1024 channels) 225, 250 MHz bandpasses Injected tones

Spectrometer & IF processor combination is stable Caltech IF processor, spectroscopic variation 10% deviation from radiometer noise at ~200 sec 30% deviation from radiometer noise at 450 sec traditional Allan time is 650 sec

Supercam spectrometer data system and integration Accumulate spectra to RAID disk array, with synchronization and header information from the TCS. Background thread on data computer performs baseline subtraction and regridding, returns single OTF spectrum every N dumps and a preprocessed integrated intensity map ~hourly. By computing TRMS continuously, data computer can determine if a scan needs to be re-observed.

Data rates, formats, storage, and archival Data cadence 2-5 Hz, typical scan rate 10-15”/s Raw data rate: 32 x 2048 x 32 bpp = 2 MB/s x Hz over ethernet Raw data will rotate off the disk to make way for new data. It will be lost in 1 week without intervention (assuming 2 TB storage array). Native format will be FITS. Optionally, user can flag that the final products be also converted to GILDAS and/or Miriad native formats. Archival: FITS headers will be written to MySQL database w/ a web frontend, so observers can search for scans and retrieve processed data. Notional search criteria: date, RA/DEC, frequency, object name.

Initial processing Quicklook Facilities By subscans: Optionally thunk raw data to 16 bpp upon writing to disk. Subtract reference scan from on-source data but store separately so that process can be undone. By rows: window and baseline-subtract entire row. Compute Trms, s, and compare to expectation from Tsys and tint. Flag observer/operator if data quality conditions not met, try adjacent reference scans, and requeue observation. By map: Perform offline regridding into Nyquist-sampled data set and extract moment maps. Quicklook Facilities Running average plot: show “64 spectra in a window” from average of last ~10 seconds End of row update, plot of data products at “end of map”. Integration with existing OTF plot at the SMT: send single beam's worth of of data to SMT TCS.