NAIC Visiting Committee Meeting · April Telescope Performance and Datataking 2009 Visiting Committee Meeting Phil Perillat

NAIC Visiting Committee Meeting · April Talk Outline Telescope performance –Pointing –Gain/Sefd/Tsys Datataking (mock pdev spectrometer) –Current status and Usage. –What we’ve learned. –Yet to be done. Online:  apr09 vc09

NAIC Visiting Committee Meeting · April Pointing Date Az Err (arcsec) Za Err (arcsec) Total Err (arcsec) 1998 mod mod mod mod mod mod Jul08-feb Pointing model made dec07/jan08 after painting shutdown.

NAIC Visiting Committee Meeting · April Pointing errors vs Za Pointing errors vs Azimuth. –Error vs az looks like a platform tilt toward td12. This gives a 1 azimuth dependence of the error. –1 platform inch rotation at 192 ft (tdCables) is 12.5 (za=2) to 18. (za=20) asecs. RmsError (za,az)=(4.6,6.8) asecs. Total=8.2 asecs. –Fine for alfa/lband. Not so great for 28 asec beam of 10Ghz. Pointing: data taken jul08-feb09

NAIC Visiting Committee Meeting · April Gain,SEFD,Tsys:lband,cband Data jul08 thru feb Mhz 5000 Mhz Gain Tsys Sefd Beam width Lband 1400 Cband 5000 Gain11K/Jy8K/Jy Tsys28 K27 K SEFD2.6 Jy3.3 Jy bmWidth204”55”

NAIC Visiting Committee Meeting · April Surface error Ruze curve shows gain loss vs surface error. –Gain=G0*exp(-(4*pi*delta/lamda)^2 –Need to pick G0.. Used K/Jy (about 75% appeture efficiency). Other factors (besides reflector error) can decrease gain: Under illuminating tertiary (cbh), bad cals, most sources extended for cbh,xband.

NAIC Visiting Committee Meeting · April Alfa Tsys Alfa tsys measured during survey runs: –1671 measurements dec08 thru feb09. –Each color is a different project: Black:A2010 (alfalfa), Red:A2048(ages), Green:A2133(auds), Blue:(A2432) –PolA on left, polB on right. –Beams 0-3 –Beams 4-6 –Beams 3,4 at highest Za for a2010.

NAIC Visiting Committee Meeting · April Mock pdev spectrometer: Status 1 box can process: –2*172=342 Mhz, in each of 4 pols (A,B,U,V), and 8192 channels/172Mhz spectrum. We have 14 boxes installed in system: –7 boxes:1/beam for primary observer –7 boxes: 1/beam for commensal observer We own 24 boxes. 1 Fileserver/box (14 fileservers). Each fileserver has 4 Tbytes of disc (14*4 = 56 Tbyes online).

NAIC Visiting Committee Meeting · April Current pdev projects: G-Alfa continuum Transit survey (GALFACTS): – 33 sessions so far. –Full stokes, 4096 channels/pol, 1 millisecond sampling with winking cal. –65 Mb/sec per box * 7 boxes = 450 Mb/sec. A 6 hour run generates 10 Tbytes. –Processing immediately after each run: Winking cal separated into calOn, calOff buffers. –Yet another fits file format (calOn,calOff buffers) 1 file has decimated in time (.2 secs) full freq range 2 nd file has decimated in freq (1.3Mhz) End up with 826 Gb per 6 hour run.

NAIC Visiting Committee Meeting · April Current pdev projects Pulsar search (PALFA) –About 15 sessions so far. –Psrfits file format used for data recording. –Convert to sigproc format for processing. –512 chan/172 Mhz, 65 Usec sampling, add polarizations in the spectrometer.

NAIC Visiting Committee Meeting · April Current pdev projects Pulsar search continued…. –I/O rates: Duty cyclePer boxAll Beams 100%32 Mb/sec220 Mb/sec 100%113 Gb/hr792 Gb/hr 80%90 Gb/hr633 Gb/hr 2hr session180 Gb/session1266 Gb/session

NAIC Visiting Committee Meeting · April Current pdev projects Alfa Ultra deep survey (AUDS):60 sessions –8192 channels, polA,B and 1 second sampling Zone Of Avoidance (ZOA):starting… –8192 channels, polA,B.1 or 1 sec sampling

NAIC Visiting Committee Meeting · April Commensal pdev usage PrimaryCommensal 1Commensal 2 Palfa pdevZoa pdev ALFALFA (wapps) Galfa galspectPalfa pdev (proposed) Igalfa galspectZoa pdevGalfacts pdev

NAIC Visiting Committee Meeting · April Current pdev projects Aeronomy: –32 Mhz time domain sampling. –Tamara hall had been working on fpga code but left. She has now been rehired as a consultant. –Student at penn state also working on this Sband radar –32 Mhz time domain sampling –Do doppler correction in fpga. –Tamara hall had been working on this but left. Luis Quintero is the new digital engineer.

NAIC Visiting Committee Meeting · April FGPA dynamic range and radars 18 bit fixed point arithmetic in fpga. Fft butterfly stages have mult and add. –Noise increases as sqrt(Number adds). Every 2 nd butterfly we downshift. –Coherent signals (radars) increase as N. Every butterfly we need to downshift. Send A/D 12 bits to upper 18 bits of register (leaves 6 bits free below). Downshift on 1 st 6+3 stages then alternate every stage. This keeps the noise from growing. If a radar is strong enough then it can still overflow the butterflies. First 9 stages are down shifts  fft<=512 can’t overflow length fft is difficult –1024*5ns/pnt=5 usecs = pulse width of faa radar. –Every sample in fft will have the radar pulse.

NAIC Visiting Committee Meeting · April A/D blanking Clipping noise is ok, clipping a radar is like clipping a sine wave, is sends power all over the spectra. Solution: –If a time sample hits the A/D limit, flag it as bad. –Any fft with a bad sample is not included in the accumulation. This resolution is 40 usecs for an 8k fft. This helps the butterfly overflow problem since overflows in the butterfly usually happen with A/D signals that hit the limits. So far everyone has decided to use this mode. This was an option that jeff mock threw in because he thought it was cool.

NAIC Visiting Committee Meeting · April Complex vs real sampling Pdev uses complex sampling The mixer image rejection works if the I,Q amplitudes are equal and the 90 degree phase shift is met. The radars push the mixers into saturation causing an image to appear on the other side. Real sampling would put mixer harmonics at a higher freq. They could then be removed with a baseband filter. –Example later..

NAIC Visiting Committee Meeting · April File formats:.pdev for time domain data (Jeff mocks origin) cimaFits for “standard” spectral line data. Galfacts fits for calon, caloff buffer storage. Psrfits for the pulsar community. Used for archiving the data. Sigproc format for the pulsar community. This is what their programs want as input. If this continues, next year I’ll use a smaller font.

NAIC Visiting Committee Meeting · April band: dynamic spectra.2 sec avg Mhz.2 sec avg. –No aeroStat –With Aerostat –Notes: 1330,1350 FAA radar 1270,1270 REMY radar 1242,1256 aerostat 1232/1248, 1242/1256 Punta salinas mode A Images of radar about 1300 (complex sampling) Radars don’t spread very far Pdev: A look at some data.

NAIC Visiting Committee Meeting · April To do.. Get single Pixel working: –1 Ghz spectra using 7*150 Mhz bands Partly in cima –Get Aeronomy working: Penn state fpga code and program being tested. –Get sband running: Needs fgpa programming (or use regular baseband sampling with pdev).

NAIC Visiting Committee Meeting · April To do.. single pixel Baseband sampling: –Need to add functionality to cima –Work on pdev headers. –7 or 14 boxes.. –Bandwith per box: Bits1pol Mhz 2pol Mhz

NAIC Visiting Committee Meeting · April Summary Pointing –Current rmsError: za: 4.6, az:6.8, tot:8.2 asecs Ok for alfa, needs az model work for high freq. How important is making the pointing better (with limited people) Gain,Tsys,sefd,Tsys –Sefd: lbw: 2.6Jy, Cband : 3.2Jy –Surface error doesn’t look terrible.. But need to work on the curve.. –Tsys alfa K –Alfa amps need leds installed for stability during radar pulses...(ganesh). Pdev –Galfacts, Auds, palfa, zoa all running. –Alfalfa.. Stick with wapps. Ages ?? –Get single pixel working –Get aeronomy and sband working Replace Mikael lerner….