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Intro

   On 07jul21 the sun was tracked with the 12meter telescope for 1 hour using the xband receiver.

    The setup was:

• The jpl horizons ephemeris was used to track the center of the sun (with an offset)
• The telescope was offset:  .125 deg Az, .124 deg El (great circle) from the center of the sun.
• data taken starting at 16:04:10 AST.
• xband receiver was used.
  
• Mock spectrometer was used to record the data.
• 7x80  MHz bands were taken  centered at:
  
• 8240,8312,8384,8456,8528,8600,8672.
• bands spaced by 72MHz so a 4 MHz overlap on each side
  
• 2 pols, 8192 channels/pol, 21 KHz channel width
• 16 bits spectra were recorded.
• the mock rms levels were set to 20 sigma (to hopefully give us some more headroom on the mocks).
  
• spectra dumped every .002048 seconds
• The datataking script can  be found in: /share/megs/phil/svn/aosoft/p12m/x101/210707_sunfs.tcl
  

We were looking for micro bursts on the sun.

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Processing the data

• Total power:
• the total power was computed over each 80MHz band. No rfi removal was attempted

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Plotting total power  vs time

    The first plots show the total power vs time at 1 second resolution (.ps) (.pdf)

• Page 1: 1 hour of data
• Each total power series has been normalized to its median value on the sun.
• Each color is a separate 80 MHz band
• offsets have been added for display purposes.
• The data has been averaged to 1 second resolution.
  
• The x axis is seconds from 16:04:10 ast (start of datataking).
  
• Top: polA,
  
• Bottom: PolB
• The vertical strips show where each data file begins (there were 26 2gb files for each band).
• there is a jump in the total power for all bands around 1860 seconds after the start. It stays high for about 100 seconds.
• about 300 seconds before the jump, the noise level increases.
  
• Page 2: blowup around the total power jump
• still 1 second time resolution.
  

    The next plot shows the total power vs time around the jump at 2ms resolution (.ps) (.pdf)

• Top: polA
• bottom:PolB

Looking at the total power dropouts

    The first set has a blowup of the total power vs time showing dropouts (.ps) (.pdf)

•  The time series is from the 8456 MHz band with 2 ms time resolution
• Top: polA 
• Middle: polB
  
• you can see some periodic dropouts.
• Bottom:
• The dropout at 225.69 seconds is over plotted
• Black has all 7 80MHz bands for polA
  
• Red has all 7 80 MHz band for polB
• The dropout is the same for all 7 80 MHz bands
• The dropout occurs at the same time for polA and polB
• there dropouts in polB occur much more often.

Spectrum of the total power dropouts

    The plots show the spectrum of the total power during the dropouts (.ps) (.pdf)

• Top: full 250 Hz bandwidth.
  
• black:polA
• red:polB  (I've added an offset for display)
• Middle: blowup of polB out to about 80Hz.
• looks like a comb.
• Bottom:
• polB spectra around 79 Hz.
• The green lines are multiples of .5 Hz
• The red dashed line is the measured comb (at 79.520368 Hz)
• at  79.5 Hz the offset from the .5 Hz comb is .0204Hz
• The comb freq is then (.0204/(79.5*2)) .500128 Hz... so it is not locked to our station clock.

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Summary:

• Data was taken for 1 hour while tracking the sun
• we saw a increase in total power (10% of the  tsys on sun)  that lasted for about 100 seconds. T
• This is probably a burst on the sun.
• We saw dropouts in the total power
• They occurred more often in polB then polA
• the lasted for about 10 millisecs
• They dropouts were the same for all 7 bands (not freq dependent).
• The dropouts were periodic. period: .500128 Hz
• Felix pointed out that this is probably the dithering of the fiber optic transmitter.
  

processing: x101/210707/p12msunfs.pro