intro

• 11-12mar19  22:30 to 02:45 AST. tracked astra1 the entire time.
  
• dome 327 receiver -> mock spectrometer
• 10 min on,offs were done
• Toward the end, two ons were done before each off.
  

Acquiring the data:

• satellite
  
• this used the gregorian dome. The 327  receiver was used.
  
• The satellite on position was tracked for 10 minutes.
• The off position was 4 beams away in za (1 deg)  from the satellite.
  
• The receiver, backend setup:
  
• 327 receiver: 53.3333 Mhz bandwidth (160Mhz/3.) 128 frequency channels, sum polA, polB. Centered at 327 Mhz.
  
• the data was piped to the mock spectrometer where the spectral density function was computed  and integrated for 9.6 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).

Two command file were used to control the experiment:

• Setup.cmd
  
• loads the mock configuration
• setups the 10 minute tracking parameters
• adjust the power
• astra1d_190312.cmd
• load ephemeris file
• 10 min on
• 10 min off
• ... repeat
• .. note toward the end we had 2 on's between the offs
  

12mar19(UTC): Observation sequence

Observation sequence:

• start time hh:mm:ss utc	on/off	object	mock filedate	mock fnum
  02:33:38	on	astra1d	20190311	0000-0008
  02:44:23	off			0100-0108
  02:55:08	on			0200-0208
  03:05:53	off			0300-0308
  03:16:38	on			0400-0408
  03:27:23	off			0500-0508
  03:38:08	on			0600-0608
  03:48:53	off			0700-0708
  03:59:38	on			0800-0808
  04:10:23	off		20190312	0000-0008
  04:21:08	on			0100-0108
  04:31:53	off			0200-0208
  04:42:38	on			0300-0308
  04:52:56	on			0400-0408
  05:03:41	off			0500-0508
  05:14:25	on			0600-0608
  05:24:43	on			0700-0708
  05:35:27	off			0800-0808
  05:46:12	on			0900-0908
  05:56:30	on			1000-1008
  06:07:15	off			1100-1108
  06:18:00	on			1200-1208
  06:28:18	on			1300-1380
  06:39:03	off			1400-1404

  
  

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 (.76 sec 327) was processed separately:
• dome 327: 79435 9.6 usec spectra /rec
• compute rms/mean for each channel (over the 79435  spectra in  a record)
• do a linear fit to the rms over the 128   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 value is within 3 sigma of the fit.
  
• This mask will be used to compute the total power for each 9.6 usec spectra .. for this .76  sec of data.
• for each of the 9.6 usec 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 9.6 usecs) for each 2.2 gbyte file of each scan.
• repeat the above for each day of data taking.

Plotting the data

    Processing the data to make the plots:

• The total power data was  scaled to sigmas, and then peaks were searched for values greater than N sigma (N = 20 , 50 sigmas)
• using the time stamps for the peaks, the width (in time) of each peak was also computed (in case adjacent values continued above N sigma).
• When adjacent peaks remained above the threshold, they were combined into a single peak with a longer duration.
  

plotting the peaks (above 20 sigma) (.pdf) (6.6 MB)
plotting the peaks (above 50 sigma) (.pdf) (3.0 MB)

• Page 1: fraction of samples above threshold (by scan)
• Top all scans in order data was taken
• Bottom: split on (black) and off (red) scans
• Page 2: peak max value and duration vs time
• colors: black+ is the on scan, red + is the off scan.
  
• top : strength of each peak vs hour of day (AST)
• bottom: duration of each peak vs hour of day
• Page 3: histogram  of number of peaks vs peak duration.
  
• Top: all data (on,off) combined
• middle: histograms for on,off data plotted separately.
• Bottom: histogram of spike duration done separately for each scan
• + are on scans, * are off scans
• Page 4: histogram of number of peaks vs duration (blowup)
• same as page 3, but the plot is blownup and uses a linear scale.
• Page 5:  max/avg value of each spike vs spike duration
• + black are on scans, * red are off scans
• The off scans have been shifted a little in duration to no overlay the ons.
• Top: max value
• bottom: average value

Summary:

• 20 sigma data
• scan 19 (on) had way more peaks above threshold than any  other scan. This was probably the 40 hz interference (more info).
• the histogram of counts vs duration showed the on's higher than the off's up to about .11 millisecs.
• Looking at the histogram by scan, 1 on scan dominates all the others (probably scan 19.).
  
•  For scans 13-19 the ons had more total peaks than the offs (including all durations)
  
• 50 sigma data
• scan 19 (on) no longer sticks out as much (the peaks must have been between 20 and 50 sigma.
  
• No clear preference for arcing from satellite.
  

processing: usr/s3043/20190311/dorfi.pro

Exporting files:

• A scan is a contiguous set of data.
• For each scan:
• 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)
• 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
  
• Headers:
• mtp_20170406_202541.hdr
  
• start1970 :                         1491510341    start time secs 1970
  timeStep  :                        0.000009600    time step seconds
  nsamples  :                           62500000    number of samples in file
  cfr       :                        327.0000000    center freq Mhz
  bandwid   :                         53.3333333    bandwidth Mhz before bad channels
  mockNmSt  :   a3164.20170406.b0s1g0.00100.fits    fname for first mock raw file
  nmockFiles:                                  9    number of mock raw files this scan
  rifname   :                                 ''    no ri files were taken

• /share/phildat/usrproj/s3043/20190311/