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Chuck says settling time is of order 1 sec.
See http://www.gb.nrao.edu/~rcreager/GBTMetrology/140ft/l0058/gbtmemo52/memo52.html for az rates vs. zenith angle.
Coverage Rate
At 35 seconds per visit and 9.6 square degrees per field, we cover the sky at a rate of 7900 square degrees in an 8 hour night. That means that on average we revisit interval (no weather) is 3 days for 18,000 square degrees.
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- What is histogram of slew times between az,alt pairs?
- Kem asserts it takes about 5 sec to slew between adjacent fields. But that's not right. Assuming we go mostly in elevation, no dome limitation, is angular acceleration limited. We accelerate for half and decelerate for half the time. So the half-slew time obeys (elevation-limited) theta=(1/2)alpha*t^2, and theta = 3.5/2 and alpha for elevation is (conveniently) 3.5 deg/s/s so t=sqrt(2*(theta/alpha)=sqrt(2) = 1.41 sec. So kinematic adjacent-field best slew time is 2.8 sec. Add one sec for settling and we get 3.8 sec, call it 4, not 5.
- ** we should take OpSim output of pointings, with rotator angle, and compute bounding boxes in RA, DEC, then import into GIS database to do rapid queries of coverage in time and filter space.
- Do maximum unobserved gap analysis for each field for each filter.
- Phil Pinto suggests computing next-field time needed as a parallel process.
- Do object-based coverage analysis rather than field-center-based analysis
Some references
LSST science book
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