• 1274.58 . smaller signal at 1269.24
• 1332.66. smaller signal at 1327.54

• 1257.6 with weaker pulse at 1252.41
• 1349.6 with weaker pulse at 1344.41

Links:
Punta borinquen carsr radar specs.

• 03oct13: blanking back on. but about 1.4 deg too early in blanking
•  assuming old blanking of 107-111 i asked them to move to 108.4-112.4
  
• may13: turned off blanking in ao direction while faa being upgraded
  

New punta borinquen carsr-3 1274,1332 MHz radar specs: (top)

09may14: punta borinquen blanking and sidelobes

    Test data was taken on 14may14 to check the FAA and punta borinquen radar blanking. The data looks at the blanking region as well as the sidelobe height over the 12 second rotation period.. The 09may14 data took 3 sets of 25 second data (2 rotations per set). The data sets were spaced by many minutes so plane echoes would not be stationary.

The setup:

• lbw, linear pol
• az=80, za=18 (this was a peak for FAA compression for alfa data taken a few years back).
• mock spectrometer 16 bit timedomain data.
• 3.2 Mhz bandwidth
• center frequencies of each 3.2 Mhz:  1257.5,1349.5,1274.5, 1232.5 Mhz
• the first two are punta del este (FAA) radar frequencies
• the last two are punta borinquen frequencies.
  
• 3 scans were taken each with 25 seconds of data.
• Start time for each 25 second scan
• 15:36:17 ast
• 15:38:17 ast
• 15:41:17
• So each scan was separated by an integral number of 12 second rotations.

Processing:

• Each 25 sec scan was input and processed
• Power was computed for each 3.2 Mhz sample
• power was averaged to 100 usecs. this is close to the 117 usec pulse length.
• polA and polB was averaged.
• The total power time series was normalized to when the radar was blanked (pointing at ao).
  
• This make the vertical scale Tsys units for AO.
• The normalized time series was then converted to db. 0db is not Tsys at AO.
  

•  Page 1: over plot 6 12 second rotations (with offsets for display)
• black red were the first two rotations starting at 15:36:17
• green,blue are the two 12 sec rotations starting at 15:38:17
• purple,dark red are the two 12 sec rotations starting at 15:41:17
• The gap at 1.1  seconds is when the radar blanks in the AO  direction.
• Page 2: average the 6 12 second rotations.
• Top: average 12 second period
• red dashed line shows the peak value (with ao blanking enabled)
• green dashed line shows close in sidelobe peak.
  
• blue  dashed line shows the far out sidelobe peak value
• The far out sidelobe is about 10db below the blanked peak. It is 16db below the close in sidelobe peak.
  
• bottom: blowup around AO blanking.
• purple vertical line: blanking specified in dod/dhs memo: 4.25 deg (.142 seconds)
• The light blue vertical line shows that the near in sidelobe is about 18 degrees from the center of the blanking region.
  
• the radar power versus rotation phase for 1274.6 Mhz radar (.ps) (.pdf):.
• The far out sidelobe is 6 db above the blanked peak.
• The radar power vs rotation phase for the 1332.6 Mhz radar (.pdf) (.pdf)
• the far out sidelobe is 9db below the blanked main beam.
• increasing the blanking by a small amount would drop the blanked peak by about 6db
  

Summary:

• the punta borinquen  blanked radar is about 23 db above the AO system temperature
• in a 3.2Mhz total power bandwidth.
• the current blanking is  .142 seconds (4.25 degrees)
• there is a large sidelobe 6db above the blanked main beam 12.6 deg from the main beam boresight.
  

04oct13: Radar blanking re-enabled.  (top)

plots,images
03oct13 before radar azimuth alignment
total power plots vs time (.ps) (.pdf)
image of total power vs rotation phase  for 79 rotations (.gif)
04oct13 after radar azimuth alignment
total power plots vs time after blanking direction updated (.ps) (.pdf):
image of total power vs rotation phase  for 17 rotations (.gif).

    The punta borinquen radar had blanking enable on 29apr13 (  more info). The pico del este radar (FAA) was upgraded to a carsr radar during the summer of 2013. During the upgrade, the punta borinquen radar was used by the FAA. The blanking was disabled sometime during this time period. On 03oct13 the blanking was re-established. On 04oct13 the blanking region was moved by 1.4 deg in azimuth to better line up with the observatory position.

    Data was taken on 03oct13 and again on 04oct13  to measure the blanking. The setup was:

• lbw receiver centered at 1330 MHz with circular polarization.
• 5 MHz IF filter followed by square law detector with  200 usec time constant
• radar interface datataking at 100 usecs/sample
  

The plots show the current state of the blanking:

03oct13 blanking before 1.4 deg move in azimuth

• total power plots vs time (.ps) (.pdf)
• Top: Total power vs 12 second rotation phase for 10 rotations. Offsets have been added for display. The dashed red line shows the start of blanking.
• The blanking is not symmetric about the beam as it sweeps through AO.
• this probably had the same azimuth blanking as 29apr13: azimuth 107 to 111 degrees in sweep.
• middle: plot of a single 12 second sweep (the y axis is a log scale). Looks like the square law detectors (or something upstream) saturated at the end of the blanking.
• Bottom: A total of 79 12 second rotations were recorded.
• The black trace shows the maximum value found .1 seconds after the end of blanking for each rotation.
• The red trace shows the same value for .1 secs before the start of blanking.
• The blanking is not centered on the ao direction. The offset is about .047 secs or .047/12 *360=1.4 degrees.
• image of total power vs rotation phase  for 79 rotations (.gif)
• 5 MHz total power about 1330 MHz was computed for each 100 usec sample.
• The data was then made into an image with the xaxis equal to 1 rotation period (12 seconds)
•  at the radar rotation period: 12 secs + 2 usecs.
• Blanking occurred between 7.3 and 7.3 seconds.
• The rotation rate should be 12 seconds. The 15 ipp pulse train (47,620.9usecs) divided evenly into 12sec +2 usecs. The residual slope comes from the 100 usecs sampling.
• Each stripe in the image is a sidelobe passing through the ao direction.
• You can see the blanking jump in units of 5 sidelobes (about 15 milliseconds in time). I think this comes from:
  
• The ipp sequence is 5*ipp1 then 5*ipp2 then 5*ipp3 giving the 15 ipp sequence
• Each set of 5 ipps lasts for about 15 milliseconds.
• the 15ippsequence divides into the 12 second period 251.990 times. There is a .01*47.62ms=.476 millisecond residual after each 12 second rotation. After about 30 rotations, the residual is equal to 15 milliseconds. They then jump a set of 5ipps.
  
• Because of this, i think the blanking will drift by about 30 or 45 milliseconds.

04oct13 blanking after blanking region moved by 1.4 degrees.

• The blanking region was 107 to 111 degrees of azimuth. I asked them to move it to 108.4 to 112.4 degrees to try and line the blanking region up with AO.
• On 04oct13 the blanking had been moved. We  then took some more data:
• total power plots vs time after blanking direction updated (.ps) (.pdf):
• Top: Total power vs time. 10 12 second rotations are plotted. The plots are blown up around the blanking region.
• The beam amplitudes before and after the blanking are now equal.
• You can compare this with the 03oct12 data by looking at the sidelobe .5 seconds after then main beam.
• on 04oct13 it is bigger than the edges of the blanked beam
• on 03oct13 the .5 sec sidelobe is a least 100 times smaller than the edge of the blanked beam
• Bottom: the maximum value before and after blanking for the 17 recorded rotations.
• Red is from the start of blanking. black measures the end of the blanking.
• The two levels are equal. So the alignment is pretty good.
• image of total power vs rotation phase  for 17 rotations (.gif). 
• The dynamic range of the data is much smaller. The vertical stripes in the image are now showing the individual ipps  from the radar (2.5 to 3 millisecs).
• The ipps before and after the blanking look similar in strength.

Summary:

• The punta borinquen radar blanking was re enabled around 03oct13. It was blanking 107 to 111 in azimuth. The blanking region was not centered on AO.
  
• On 04oct13 the azimuth blanking was changed to 108.4 to 112.5. This was not centered on the AO direction
• The blanked main beam is not smaller than the sidelobe at +15 deg in azimuth.
• The radar blanking jumps jumps by units of about 15 milliseconds. The jump occurs after about 30 rotations (30*12)=6 minutes.
  
• I think this comes from the15 ipps sequence not dividing evenly  into 12 seconds.
  

29apr13: measuring the radar blanking (top)

    On 29apr13 i spoke with MS Sgt Bezos about the radar blanking in our direction. He had the radar blank 107 thru 111 degrees of azimuth (as it points at the AO). Spectra were taken before and after the blanking. Total power data was taken after the blanking was in place.

total power data:

    After the blanking was turned on data was taken with  the lbw receiver was centered at 1274.5 MHz. The setup was:

• lbw centered at 1274.5
• The signal was passed through a 5 MHz filter and then detected with a 2 usecond time constant.
• The detected signal was sampled at 1 MHz with the ri (12 bits).
• This was done for 48 seconds (4 radar rotations)

• The data was sampled at 1 usec but then smoothed,decimated to 40 usecond resolution.
• Each rotation is plotted in a different color (with offsets for display)
• The top frame is plotted vs time. The blanking occurs around 3.5 seconds.
•  The bottom plot is plotted vs azimuth (of the radar). They told me they blanked from 107 to 111 degrees of azimuth.
  
• For the azimuth, i used the first  signal dropout to be az=107 degrees. This is where they told me they started blanking.
• I don't see very strong backlobes of the radar.

• The 4 rotations have been over plotted (using different colors).
• top frame: plotted vs time
• the radar is blanked from 3.565 to 3.717 = .152 seconds
• bottom frame: plotted vs azimuth
• the radar is blanked from 107 to 111.62 degrees (assuming 107 is the first drop off).

Spectral data:

• The interim correlator used 9 level sampling, 1 second integrations.
• 12 1 second spectra show a complete radar rotation (with offsets for display)
• The white traces are with no blanking.
• The red traces are with blanking turned on.
• The traces with blanking on actually look to be the same strength as when blanking is turned off.
• The limited number of bits may have been clipping the signal at a level outside the blanking region
• A better test would have been to look outside the radar freqeuncy and see if the system was compressing less when the blanking was on.

Rfi hilltop monitoring:

    The rfi hilltop monitoring data at the radar frequencies was plotted for 29apr13 (.ps) (.pdf):

• The black trace shows the 1274.5 Mhz peak. The red trace is the 1332.5 Mhz peak
• The green line shows where the blanking was enabled.
• The max value prior to blanking was -14dbm.
• the max value after blanking was -25dbm
• So the blanking lower the signal by about 11db..
  

Summary:

• The punta borinquen radar began blanking the radar when it pointed at AO (on 29apr13).
• The radar blanked for azimuths 107 - 111 degrees of azimuth.
• Using the interim correlator, the radar spike remained about the same (before and after blanking).
• The hilltop monitoring saw the radar signal decrease by about 11db when blanking was enabled.
  
• We probably need to see if the radar is compressing the system with it's current blanking window.
  
• After the radar is accepted we may try to get them to increase the blanking window.
  

23apr13: First look at the radar. (top)

    Data was taken on 23apr13 to characterize this new radar. The setup was:

•  za=2,az=286. Telescope was stationary during the datataking.
• lbw receiver, linear polarization, no filters.
  
• mock spectrometer
• file:000 - cfr=1300 MHz, 172 MHz bw, .1 second sampling of spectra. Take data for 60 seconds. starting around 11:45.
  
• file:100 - cfr=1271.5, 8.6 MHz bw, time domain, 8 bit sampling, 25 seconds of data.

• The dynamic spectra shows which birdies are coming from the same source.
• The radar rotate with a period of 12 seconds. When the radar points at ao, the birdie gets stronger
• Common radars:
• Punta salinas: 1232.65, 1241.60, 1247.77, 1256.59
• punta Borinquen: 1269.44, 1274.48, 1327.52, 1332.56
• FAA Radar: 1330,1350
• You can see that the 1274/1332 radar is not rotating the same as punta salinas or the FAA radar.

• Page 1: 60 second average of the 172 MHz bandwidth centered at 1300 MHz
• Top full band. the new radars are flagged in color
• the 1269 and 1327 birdies are much weaker than the other two.
• Middle,bottom:blowups  around the new radar frequencies.
• The bandwidth is about 1 MHz
• The signal probably saturated when it pointed directly at us.
• Page 2: Total power times series (.1 second resolution).
• top: 60 seconds of data. red is 1274.75, green is 1332.7 MHz. Blue vertical lines are placed every 12 seconds (the rotation period of the radar).
• Bottom: blowup when the radar pointed at AO.

• the signal was I/Q sampled at  8.6 Msamples/second centered at 1271.5 MHz. This contained th 1274.5 and the 1269 birdies.
  
• The total power was then computed for each sample (polA and B was then averaged).

Total power vs time folded at cumulative ipp of radar (.gif)

• The total power data stream was searched for the radar ipps
• There is a sequence of  5*ipp1 , 5*ipp2,5*ipp3. So the pattern repeats every 15 ipps.
• The image shows the total power data plotted  at this 15 ipp power.
• For the image the data was smoothed/decimated by 100 (to a resolution of 11 usecs).
  
• the 15 ipp period is 47.62088 milliseconds.
  
• You can see the 3 times when the radar pointed at the AO (the bright points).
• The narrow line to the right of the radar may not be real.
  
• The 8 bit samples saturated. squaring to get the power gave a constant output value for a few samples.
  

• Top: total power showing pulse duration. This .11 usec resolution.
  
• The first pulse lasts for 117 usecs
• there is a gap of about 150 useccs
• then a narrow pulse of 19 usecs.
• The power included the 1274.5 and the 1269.4 birdies.
  
• The blank space is probably when the  1332 and 1327 mhz pulses were active
• So then entire pulse period is about 300 usecs.
  
• Bottom: 25 seconds of data folded at the cumulative radar ipp: 47.62088 milliseconds
• The 3 different ipps are flagged in color

Summary:

• the punta borinquen carsr radar on 01apr13 around 14:00
• The radar frequencies are:
  
• freq: 1274.58,1332.66 with smaller birdies 1269.24,1327.54 MHz
• The large birdies are separated by 58 MHz

• The smaller birdies are 5.12 MHz below the larger birdies.
• Bandwidth : about 1 MHz
  
• ipps:
• 3 ipps: 2755.4, 3150.7, 3627.5 usecs
• Each ipp is repeated 5 times, then it steps to the next ipp
• The  15 ipp period is : 47.62088 milliseconds.
• Rotation period of  12 seconds.
• pulse length and order:
• 117 usecs 1274.5, 117 1332.5, 19 usecs 1327, 20 usecs 1269 MHz.
  
• The bandwidth at each freq is about 1 MHz.
  
• The radar will finish acceptance testing on 15may13.
  
• Problems:
• I think the 1332 MHz radar is interfering with the radar blanker.
• The radar blanker generates a total power time series with the 1330,1350 radar folded together.
• Unless there is a pretty narrow filter, the 1332 radar will end up in this time series.
• when the blanker searches for the FAA radar, it may get confused by this other set of pulses.
  

processing: x101/130423/lbwrdr_spc.pro  lbwrdr_tmd.pro

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