Progress Report on Software Spectrometer Development for GALFA



Date: Wed, 03 Sep 2003 17:43:40 -0400
From: Jeff Hagen 
To: rbrown@astro.cornell.edu, goldsmit@astrosun.astro.cornell.edu,
     desh@naic.edu, satorchi@naic.edu
Subject: GALFA software spectrometer


Hi Bob,

You asked me to give a short status report on the GALFA software 
spectrometer.

Paul Goldsmith gave me the Heiles signal processing document and I have
implemented those changes. This includes the ability to do fft overlaps
and Welch weighting.

Current performance status:
  - 2.4GHz dual xenon motherboard
  - 8192 spectral channels
  - Welch weighting
  - overlap factor of 3 (this is up from olap=2 that I reported to Paul
    several weeks ago.)
  - 40 MB/second (16 bit I and 16 bit Q).  This refers to one polarization
    at 10MHz or dual pol at 5MHz bandwidth.
  - The digitizers run at 80 MHz and are digitally filtered and down 
converted
    (from 30 MHz) in the graychip.

The next step is to do a practical test taking a standard on/off on the
telescope. I am going to finish the WAPP spectral line project first
as I can easily use the same software to produce the single dish FITS
data format. With a working WAPP spectral line mode, a software
spectrometer mode is an easy step.

Jeff