intro

• 29sep16:
  
• Dome 327 Mhz Rcvr tracking the gps satellite
• 30sep16:
• Dome 430 Mhz rcvr tracking the gps satellite

Acquiring the data:

• satellite
  
• this used the gregorian dome. The receivers used were 327 and then 430 dome receivers.
  
• The satellite position was tracked or a position 3 beams offset ( great circle azimuth) from the satellite.
  
•  The two receivers used were:
• 430 receiver: 26.6667 Mhz bandwidth (160Mhz/6) 128 frequency channels. Centered at 432 Mhz.
  
• 327 receiver: 53.3333 Mhz bandwidth (160Mhz/3.) 256 frequency channels. Centered at 327 Mhz.
  
• the data was piped to the mock spectrometer where the spectral density function was computed  and integrated for 19.2  micro seconds
• the spectra were output to fits files:
• A continuous (in time) data set (called a scan)  consisted of multiple fits files (each about 2.2 gbytes).
• rfi beam:
• This used the carriage house receiver:
• the postion was 180 Degrees from the satellite. The za was fixed at the stow position (8.8343 deg).
• The data was piped to the ri a/d converters.
• complex voltage samples were taken at a .5 usec sampling rate (giving a 2 Mhz bw), 8 bit samples, and then written to disc.
• The 430 Mhz receiver was used (centered at 430 Mhz)

A 10 minute on, off cycle was used:

• 10 minutes pointing at the satellite
• 1 minute to move 3 beams from the satellite (in great circle azimuth)
• 10 minutes pointing off the satellite.
  

29sep16 (AST): 327 receiver

Observation sequence.

• 160930(UTC) (160929 AST): dome: 327 rcv, ch : 430 monitoring.

• start time hh:mm:ss utc	on/off	object	mock fnum	mock rcvr	ri File nums	ri rcvr	notes
  00:50:53 to 01:01:00	on	gps prn 18	000 - 007	327	001-002	430 ch
  01:02:01 to 01;12:00	off		100 - 107		003-004
  01:13:01 to 01:23:00	on		200- 207		005-006
  01:24:00 to 01:34:00	off		300- 307		007-008
  01:3500 to 01:54	on		400- 415		009-011		The satellite started to go out of the beam between 01:58:00 and 01:59:00.
  01:56:00	off		500- 507		012-013		we were more that 3 bms from the satellite since it had set.

30sep16 (AST): 430 receiver

• 161001(UTC) (160930 AST): dome 430 rcvr, ch: 430 monitoring.

• start time hh:mm:ss utc	on/off	object	mock fnum	mock rcvr	ri File nums	ri rcvr	notes
  00:46:00 to 00:56:00	on	gps prn 18	000- 004	430	000-001	430
  00:57:00 to 01:07:00	off		100- 104		002-003
  01:08:00 to 01:18:00	on		200- 204		004-005
  01:19:00 to 01:29:00	off		300- 304		006-007
  01:30:00 to 01:50:	on		400- 408		008-010		Continue tracking satellite till it set
  01:51:00 to 02:01	off		500- 504		011-012		satellite more than 3 bms away since it had set.

  
  

Processing the data:

• deltaTsys/Tsys = 1/sqrt(channelBandwidth*time)
• (Since we've added polarizations, the channel bandwidth has been doubled..)
• So computing the rms by channel and then normalizing to the average channel value will give sigma values that should be determined by the bandwidth and integration time.. if the signal is noise like.. Any intermittent rfi (narrow channel frequeny broadcasts) will increase the rms values in these channels..
  
• broad band bursts from the satellite that lasts for 10's of usecs will not affect this  (since they are too short in time).
• PolA and polB were added together in the mock spectrometer, before outputting the spectra.
  

Satellite beam:

• each row of data (1 sec 430, .8 sec 327) was processed separately:
• dome 327: 40325 19.2 usec spectra /rec
• dome 430: 52080 19.2 usec spectra/rec
  
• compute rms/mean for each channel (over the 49325 ir 52080  spectra)
• do a linear fit to the rms over the 128 or 256  freq channels (excluding the edge channels where the analog/digital filter) response fell off.
• Create a freq channel mask that includes all freq channels whose fit is within 3 sigma of the fit.
  
• This mask will be used to compute the total power for each 19.2 usec spectra .. for this 1 sec of data.
• for each of the 19.2usec spectra in the row () compute the total power using the above row
• output the data, and record which frequency channels were used for this row.
• repeat the above for each file of the scan
• and continue for each scan of the day.
• There will be 1 output file of floating point total power data (sampled at 19.2 usecs) for each scan.
• repeat the above for each day of data taking.

RFI BEAM:

• this was 2 Mhz of complex voltage samples, centered at 430 Mhz.
• all of the files comprising a 10min scan ( 8bit complex voltages) was read in.
• the mean was subtracted from the i, q channels (to get rid of DC offsets)
• the power was then computed for each .5 usec sample , and then averaged to 10 usecs.
• the mean and rms was then computed for the entire data set.
• the output values were the tpOut[i]= (tpAvg[i] - mean)/rms
• Comparing the two beams.
• This is used when the on source an rfi beams are both 430 Mhz...
  
• If we find a large sigma in the on source beam, we should check the same time (and maybe 10 usecs on each side) to see if there is a corresponding large sigma in the rfi beam..
  
• If this is true, then the sigma in the on source beam is not from the satellite.
• Passing this test does not guarantee that the on source large sigma is from the satellite..
  
• the rfi bandwidth is only 2 Mhz.. there could be some frequency channels outside this 2 mhz that has terrestrial rfi.
• broad band interference (say lightning)  may appear in both the satellite beam (at 327 Mhz) and the rfi beam at 430 Mhz.
  

Decide which broad band spikes to keep.

• The satellite beam total power array was converted to sigmas.
• sigSat[i]=(tpSat[i]- mean(tpSat))/rms(tpSat)
• The rfi beam was already in sigmas
  
• to be a valid  broad band spike, the point had to meet:
• the sigSat[i]  had to be larger than the sigma threshold (say 5 sigma)
• the sigRfi[j]  had to be less then the sigma threshold
  
• For every sigSat[i] point, 3 points were checked in the sigRfi[j] array (the one closest, 1 above, and 1below in time)
• If any of the 3 points in the sigRfi array were > than the sigma threshold, then the sigSat[i] point was ignored.
• The satellite spikes should be narrow in time .. say up to 100 usecs..??
  

Exporting files:

• A scan is a contiguous set of data.
• For each scan:
• there is are two data sets:
  
• there is a data set from the gregorian dome, mock spectrometer
• this is the beam that pointed at or close to the satellite
• the files start with mtp_ (mock Total Power)
• There is a data set from the carriage house, ri a/d interface
• This is the beam that pointed 180 degrees from the satellite (rfi beam)
  
• the files start with rtp_ 
• Each data set has:
• file of total power data (4 byte floating point, little endian)
• Equally spaced in time
• ends with .dat
• an ascii  header file that has some info on the scan
  
• Filenames:
• mtp_yyyymmdd_hhmmss.dat / .hdr
  
• The date, time is the utc start time for the data in the file
  
• rtp_yyyymmdd_hhmmss.dat/hdr
• The date, time is the utc start time for the data in the file
• Note: the mtp and rtp files do  not necessarily start at the same second
• Headers:
• mtp_20160930_005053.hdr
• start1970 :                         1475196653    start time secs 1970
  timeStep  :                        0.000019200    time step seconds
  nsamples  :                           31655125    number of samples in file
  cfr       :                        327.0000000    center freq Mhz
  bandwid   :                         53.3333333    bandwidth Mhz before bad channels
  mockNmSt  :   s3099.20160929.b0s1g0.00000.fits    fname for first mock raw file
  nmockFiles:                                  8    number of mock raw files this scan
  rifname   :                rtp_20160930_005110    basename (or none) for ri tp (rfi beam) file
  
  
• rifname specified the ri  file that corresponds to the  mock total power file
• rtp_20160930_005110.dat
  
• start1970 :                         1475196670    start time secs 1970
  timeStep  :                        0.000010000    time step seconds
  nsamples  :                           59252736    number of samples in file
  cfr       :                        430.0000000    center freq Mhz
  bandwid   :                          2.0000000    bandwidth Mhz
  riNmSt    :                 s3099.20160929.001    fname for first ri raw file
  mfname    :                mtp_20160930_005053    basename for mock tp (on beam) file
  
  
• mfname is the mock file that goes with this ri file.
  

• /share/phildat/usrproj/s3099/export/
• (and also a copy on gpuserv0.. but this is not exported to the rest of the network).

link to sep16 data directories

• 20160929.tar  .. is a tar file with the .hdr and .dat files from 29sep16 (ast dates)
• 20160929/       .. is a directory holding the individual files (the tar file was made from this)
  
• 20160930.tar  .. is a tar file with the .hdr and .dat files from 30sep16 (ast dates)
• 20160930/       .. is a directory holding the individual files (the tar file was made from this)