|
|
发表于 2005-9-20 10:18:31
|
显示全部楼层
为什么03年的数据还在算?
Okay. I must have answered this in three other threads pertaining to this same topic already. But perhaps let me add a little more info this time that may shed light on the '03 data.
Data tapes come from Arecibo and end up in a pile next to my desk. We have, on average, a backlog of about 6 months' worth of tapes to split into workunits. There's no care taken to keep these tapes in chronological order (there's no need to, and there's better things to worry about). When it comes time to make more workunits, I grab a random tape.
This stuff I already mentioned elsewhere. BUT! There's more: We do actually check the quality of the data before throwing it into the splitter - we don't want to make a bunch of workunits with excessive RFI, or machine noise because the telescope was under maintenance, etc. Basically every two hours we compare the current spectrum we are recording against what we'd expect to see, and if it's WAY off, we probably have garbage data (so WAY off that we are positively not throwing out ET signals but obvious earth noise clobbering the relatively quiet noise from space).
Back in 2003 we had our large backlog of data, so we had a chance to be more selective with our tapes, not splitting anything that had the chance of being bad data. So a lot of 2003 tapes never made the cut at that time. Since then, we have determined that perhaps we were being a bit too selective - some of the data checks were failing the same time every day (perhaps this was a reflection of sun position affecting our receiver - I'll leave that up to the real scientists around here to decide). I was also cutting tapes when it failed a data check 1 time out 8, thus "throwing away" 87.5% of good data because 12.5% seemed squirly.
But of course we keep these tapes around, so this data wasn't actually thrown away - just settling to the bottom of my data tape box for later reconsideration.
That's all.
- Matt |
|
发表于 2005-9-16 17:34:45