<div dir="ltr"><div>Hi All,<br><br>Related to the "NSTOT" idea --<br><br>In fold mode data, it's not currently possible (I don't think) to consistently determine how much data is in a file in the sense of being able to accurately compute the radiometer noise level.<br>
<br>For DFB data, one can recover it from DAT_WTS as they all are set to 1 initially and no online RFI zapping is performed. However, I think this behavior isn't guaranteed.<br><br>For dspsr instruments, the weights don't seem to be normalized in this way. (Presumably they account for RFI zapping etc. in a relative sense, though.)<br>
<br>I'd propose something like "NSAMP" for each subint -- a dimensionless number giving the product of the total (actual) bandwidth and observing time in the subint, i.e. the number of field samples. Then, provided the DAT_WTS are at least proportional to the actual channel bandwidth, this number can be updated through scrunching and zapping operations, and one can always accurately determine the radiometer noise floor.<br>
<br></div><div>If DAT_WTS couldn't be used in this way (e.g. if one had S/N weighted?), another option would be to introduce a DAT_NS array shaped like DAT_WTS but giving nsamp for each channel & subint. A cost of 256 KB for a typical 64-subint, 1024 channel observation.<br>
<br></div><div>Accounting for npol could either be left as an exercise for the user or incorporated in the above.<br></div><div><br></div><div>Cheers,<br>Matthew<br></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">
On 3 May 2014 02:39, Willem van Straten <span dir="ltr"><<a href="mailto:vanstraten.willem@gmail.com" target="_blank">vanstraten.willem@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">Hi Dick,<div><br></div><div>LEVSEPN and NSTOT sound like very sensible additions to me. OBSDESCR also sounds like a useful way to log the unexpected and anomalous. Also, patterns might arise in the use of this free-format text that lead to the identification of new, useful parameters that are added to the definition (and can be parsed by automated tools).</div>
<div><br></div><div>Cheers,</div><div>Willem</div><div><br></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On 2 May 2014 12:32, <span dir="ltr"><<a href="mailto:Dick.Manchester@csiro.au" target="_blank">Dick.Manchester@csiro.au</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div style="word-wrap:break-word;color:rgb(0,0,0);font-size:14px;font-family:Calibri,sans-serif">
<div>Hi all</div>
<div><br>
</div>
<div><span style="font-size:medium">
<div style="font-size:14px;font-family:Calibri,sans-serif">Partly as a result of some discussion about encoding and decoding of 2-bit data, George Hobbs has requested that the PSRFITS definition include a specification of the digitisation. I'm proposing
a new version of the definition (v5.4, attached) which includes a parameter "LEVSEPN" in the Digitiser Counts table. This is defined as the separation of the digitisation thresholds in units of the input rms value. Also at George's request, I'm proposing a
new binary OBSDESCR table, which is simply free-format text where any information related to the observation or the processing can be stored, and a new parameter NSTOT in the SUBINT table main header, which is the actual number of valid samples in a search-mode
file (the last subint is often incomplete).</div>
<div style="font-size:14px;font-family:Calibri,sans-serif"><br>
</div>
<div style="font-size:14px;font-family:Calibri,sans-serif">Please send any comments (using "reply all") on these changes or other suggested changes to the definition by Tuesday May 6.</div>
<div style="font-size:14px;font-family:Calibri,sans-serif"><br>
</div>
<div style="font-size:14px;font-family:Calibri,sans-serif">Regards</div>
<div style="font-size:14px;font-family:Calibri,sans-serif"> Dick</div>
<div><br>
</div>
</span></div>
</div>
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