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This presentation by Phil Perillat outlines essential insights into the telescope's performance and data acquisition capabilities as of 2010. Key topics include pointing accuracy, gain, SEFD, and Tsys measurements across different bands, as well as limitations of the new telescope observatory. It also covers advances in data-taking backends, commensal observing techniques, and future improvements. Enhance your understanding of modern astronomical instrumentation and its operational dynamics by delving into these findings accessible via the provided online resource.
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Telescope and Datataking status 2010 Visiting Committee Meeting Phil Perillat
Talk Outline • Telescope performance • Pointing • Gain/Sefd/Tsys:cband,lband, 800 Mhz • New telescope observing limitations • Datataking: • Backends • Commensal observing • Future • Backends • 12 meter • Summary Online: http://www.naic.edu/~phil/talks/talks.html apr10 vc10
Pointing • Pointing model made dec07/jan08 after painting shutdown.
Pointing Errors: mar09-mar10 • Mar09-jan10 data before break • Errs vs za • Errs vs az (1 az term y08-09 removed in model) • Mar10: after beam repair: • Errs vs za (limits: 3.5 to 12 deg za) • Errs vs az (looks like 1az term..) • RmsError: • Before break: 4.9,6.3 (za,az). Tot: 8.0 asecs • After break: 9.0, 10.6 (za,az). Tot:13.9 asecs
Gain,SEFD,Tsys:lband,cband • Data mar09 - mar10 • Lband @ 1400Mhz • Cband @ 5000 Mhz • Gain • Tsys • Sefd • Beam width
700-800 Mhz rcvr • Installed jul to dec09. penn state feed • Cooled to 70K, cavity filter in front of lna. • Gain,Tsys: Tsys high.. Cavity filter, over illuminates tertiary. • Sefd ,BeamWidth • Rfi: Chn 67 (879 Mhz) LP tv. • Helped buy parts for lp dtv so they would go off the air • BYU single pol rcvr 5% smaller bm width • Still working on dual pol mode. • Running out of time for clean band: • Emg services: 763-775,793-805 ready to go.
Alfa • Alfa tsys measured during survey runs: • 4048 measurements mar09 thru mar10. • Each color is a different project: • White:A2010 (alfalfa), Red:A2048(ages), Green:A2433(auds), Blue:(A2453) • PolA on left, polB on right. • Beams 0-3 • Beams 4-6 • Beam 2a has unstable Tsys.
observing limitations • The weights and distances on az arm. • Za for dome center of mass: 1.9deg below optic axis za • Ratio DomeWeight/ChWeight = 6. • For constant moment arm: dzaCh = 6*dzaDome. • How we observe: • Ch sits at 8.8 degrees, dome moves in za. • Azarm imbalance changes with dome za. • Elevation rails shimmed high so imbalance tilts receiver in dome, onto the paraxial surface. • 3 tiedowns keep the average platform height fixed with temperature (no tilting of platform done by td’s)
The problem: • Max allowed imbalance:15000 kip-ft • Various configs for ch, dome motion: • BUT: max allowed imbalance depends on td tension • Td tension relieves tension in beams. • Td tension used to keep avg platform height in focus. • This is a function of temperature since main cables change length with temp. • Examples showing za range vs temp: • Dome tracks: Ch at stow: normal astronomy • Dome tracks: Ch tracks dome above 8.8 deg za • Dome tracks: Ch at 0 (aeronomy az swings).
What we can do: • Removing weight from the dome • decreases the unbalanced moment arm • Removing weight from the platform • Allows more tension in the tiedowns • Installing the tertiary motor drives. • Lets you make the optical axis longer • This lets you increase the td tension (pull down on platform) to get back in focus. • 1 platform inch is 2-3 kips per corner • 1 deg F is .75 kips per corner.
Datataking:new functionality • Mock single pixel observing • 7x172Mhz covers 1Ghz IF with 20Khz res. • 1 Ghz, 10Khz res. Possible with 2nd 7x172 set • Different settings allowed for 7 bands: • Center freq, channels, bw, config:sumPols, 2pol, stokes. • Mock file server upgrade: • 3.2 -> 5.5 Tb/server. TotalDisk:14*5.5=70 Tb online. • Mock aeronomy sampling system • 6 bands: 32Mhz widest, samples @160Mhz • Example:10 sec clp spectra (ch)
Datataking:Commensal • Alfalfa extragalactic search, short integrations, large area • Ages – extragalactic search, median integration • Auds – extra galactic search: long integration • Zoa : zone of avoidance • Galfacts: galactic polarization survey • Rrl: recombination line survey • Togs- galactic survey • Palfa: pulsar search. • Survey names: • Routine survey commensal observing: • Example: • Igalfa/galfacts/zoa,rrl: may09-sep09 56 3hour sessions • Igalfa- galactic survey galspect, • Galfacts: mock,full stokes, 300 Mhz Bw. • 65Mb/sec *7 =455 Mb/sec, 4Tb/night • Zoa/rrl:mock2, 300 Mhz Bw, .1 sec integrations.
Future:Backends • Vlbi: Digital BackEnd: dbe • 2: 1 for 305meter, 1 for 12 meter • Has mode to run 500 Mhz bw spectra • Aeronomy • Integrate mock device with datataking. • Planetary radar with mock: • Needs fgpa programming (or use regular baseband sampling with pdev).
Future:Backends • Mock single pixel Baseband sampling: • Need to add functionality to cima • Work on pdev headers. • 7 or 14 boxes.. • Bandwith per box:
Future:12 meter • 12 meter telescope • Integrate with vlbi station observing using dbe • Allow non vlbi usage of telescope with 305m • Needs pointing program • IF signal needs to be piped into standard backends. • Software to support it.
Summary • Telescope performance: • Pointing: • rmsError: za: 9.0 az:10.6 tot:13.9 asecs • Need to fix 1 az term from tilted platform • Gain,Tsys,sefd,Tsys • Sefd:800:13.Jy, lbw: 2.5Jy, Cband : 3.3Jy • Get 800 antenna replaced • Tsys alfa 26-35 K (vs za). fix bm2a. • Limitations: • Za 3.5->12, daytime fixed position. • Future: • 12 meter integration. • Backends: • Integrate aeronomy, do planetary radar, mock baseband sampling.
