190112-190114 : Satellite arcing experiment
12-14 Jan 2019
2019
links
Acquiring the data
observation sequence
processing the data
plotting the data
summary
exporting the files
intro
s3043 was looking for arcing signals from
satellite solar panels (more info).
gps prn28 satellite was tracked for the 3 days.
Data was taken on:
- 12-14jan19 00:00 to 03:00AST. tracked gps28 the
entire time.
- dome 327 receiver -> mock spectrometer
- 10 min on,offs were done
Acquiring the data:
Only 1 set of data was acquired (there was no
separate beam to detect rfi).
- 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
- satellite command files:
- gps28_190112.cmd gps28_190113.cmd
gps28_190114.cmd
- load ephemeris file
- 10 min on
- 10 min off
- ... repeat
12-14jan19(UTC): Observation
sequence
Observation sequence for gps28
-
start time
hh:mm:ss
utc |
on/off |
mock file date
|
mock
fnum |
12jan19
|
04:41:19
|
on
|
20190112
|
0000-0008
|
04:52:10
|
off
|
20190112 |
0100-0108
|
05:02:52
|
on |
20190112 |
0200-0208
|
05:13:40
|
off |
20190112 |
0300-0308
|
05:24:28
|
on |
20190112 |
0400-0408
|
05:35:10
|
off |
20190112 |
0500-0508
|
13jan19
|
04:37:14
|
on |
20190113 |
0000-0008 |
04:48:04
|
off |
20190113 |
0100-0108 |
04:58:47
|
on |
20190113 |
0200-0208 |
05:09:35
|
off |
20190113 |
0300-0308 |
05:20:23
|
on |
20190113 |
0400-0408 |
05:31:06
|
off |
20190113 |
0500-0508 |
| 14jan19 |
04:33:12
|
on |
20190114 |
0000-0008 |
04:44:02
|
on |
20190114 |
0100-0108 |
04:54:44
|
off |
20190114 |
0200-0208 |
05:05:32
|
on |
20190114 |
0300-0308 |
05:16:19
|
on |
20190114 |
0400-0408 |
05:27:01
|
off |
20190114 |
0500-0508 |
|
|
|
|
Processing the data:
From the radiometer equation we have that:
- 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 frequency
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.
- 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
20190112 plots:
20190113 plots:
20190114 plots:
Summary:
- 13jan19 clearly shows more spikes in the on than the off (2 to
3 times more at 20 sigma, 4-5 times more at 50 sigma.
- 14jan19: on scans have more spikes than off scans.. not as
obvious as 13jan19.
processing: usr/satarc/20190311/dorfi.pro
Exporting files:
Each days data are stored under a separate
subdirectory (the directory names are the utc dates when data was
taken):
- 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
processing:usr/satarc/20190112/*.pro (lots of
programs)
rawdata: sitting on:gpuser0: /media/DATA0/phildat/s3043
exportable data on:
- /share/phildat/usrproj/s3043/20190112-14/
home_~phil