[evla-sw-discuss] pulsar data

[Tim Hankins]

My 2 cents:
   I've hardly been in the loop on the correlator discussions, but  
I'd like to offer a couple of comments on today's discussion.
   1. Gating: Multiple gates per period, e.g., on-pulse and off- 
pulse, are desirable for HI obs or other observations where one is  
looking for weak emission near the pulsar. Obviously separate  
accumulators are required. Does phase binning take care of this?
   2. Specification of pulsar ephemeris: on my own data acquisition I  
specify the pulsar name and frequency, and the "system" computes the  
polynomial at the start of the observation (takes about 2 seconds),  
based on pulsar ephemeris PARAMETERS obtained from  people who  
generate these things for a living. This has proven to be far more  
reliable than independent polynomial generation and subsequent  
transfer to the observing system. And it allows flexibility in case  
of interference, receiver problems, etc.
   3. Realtime pulse phase adjustment: For many pulsars the predicted  
phases are pretty good, even a year ahead. But I suspect that there  
will be many interesting pulsars for which they are not so good. The  
ability to refine a gate or sampling window in real time would be  
very nice, (I do it with mouse driven cursors; credit to Jeff Kern)  
and may lead to improvement in efficient array utilization. Going  
back to the same pulsar two weeks later may just not work.
   4. Binning: The observer will want as much time resolution as he  
can get, so the ability to "bunch" bins would be nice. If not, can  
the number of bins per pulse period be a power of 2 for more  
efficient post-processing FFTs?
   5. Multiple subarrays: I would guess that the most often use of  
this capability is for multiple frequency observations of one pulsar.  
Sounds like this is no problem.
   6. I don't recall if there is a (digital) output "spigot" like the  
current "analog sum" for phased array use. VLBI? Real fast, single  
pixel, backends?

   Tim Hankins