Hi Tim and Jacek, Just to play devil's advocate, we may need quite a bit more than 6 TB of template images. While we may only take 1000 images between astronomical twilights, we may not be able to accurately predict which fields and filters these will be. Variable conditions may push us to observe fields which are lower priority. We may also do z and y observing in twilight conditions which gives us a few hundred more field/filter combinations. We may also need color information for diffraction correction calculations. Might we also need our templates to be better than integer precision?
Baseline with twilight observing: 1200 images x 6.4 GB/image X 0.80 unique area = 6.1 TB perfect planning x2 for color information x2 for float x1.3 for spare field/filters for unpredicted weather/seeing backup gulp, 31.7 TB (! upper limit, I hope) Kem > Hi Jacek, > > Here's a rough calculation. I assume a typical night of 10 hours, > which corresponds to about 1000 observations of distinct fields (sky > positions). For each of those sky positions, we need at the base: > > a) Template images for the fields. At roughly 6 GB/image, that gives us > 6TB > > b) Recent catalog data for all objects in the fields brighter than about > V=25. How much data that is will vary quite a bit, as a previous email > I sent out explains in some detail. For present purposes, I assume > that there are 150000 objects/deg^2 that qualify. I assume that for > each object we need summary information, which I estimate at 200 bytes > (very rough), and the latest 10 epochs of measurements at 50 bytes each. > This then gives us 1000 fields * 150000 * 10sq deg * (200 + 10*50) = > 1.5TB. I'd say at present this is no better than a factor of two > estimate. > > c) calibration images - this is maybe 100GB, negligible. > > So a rough guess is 7.5TB. > > Cheers, > Tim > > Jacek Becla wrote: >> Jeff/Tim/Ray >> >> I'd like to start thinking about details of pre-staging >> data at the base / partitioning it, but before I do that >> I need to understand how much data we are talking about >> per night (the question was brought up at today's Database >> telecon). >> >> If you could find that out and give me even a rough estimate >> whether it is a terabyte or a hundred terabytes, that >> would help a lot. >> >> Thanks, >> Jacek > _______________________________________________ > LSST-data mailing list > [email protected] > http://www.lsstmail.org/mailman/listinfo/lsst-data > _______________________________________________ LSST-data mailing list [email protected] http://www.lsstmail.org/mailman/listinfo/lsst-data
