x111 rfi monitoring data
lband dynamic spectra images
Taking the data: (top)
rfi monitoring data (project x111) is taken
whenever there is any unused telescope time. The setup is:
- Use interim correlator to take the data
- 9 level sampling,1 second dumps, 60 seconds of data followed
- use 4*25 MHz bands at each integration
- Offset the 4 bands in freq by 23 MHz (so there is some
- The telescope is stationary when the data is taken (so the sky
drifts through the beam).
- For each receiver start at the lowest frequency and move
in 23*4 MHz steps every 65 seconds until the entire band
- When a band is complete, move to the next receiver.
- continue cycling till the operator aborts the program.
- The information to control the program is in
- x111auto.corsu .. interim correlator setup
- x111auto.proc (in /home/online/Tcl/Proc/astro/cor) tcl
command to run at the vw% prompt in vxWorks to run the
- file containing all of the receivers and bands to observe.
- The program x111auto just steps through this file.
- x111auto.exc - list of receivers to ignore. Any receiver
names in this file will be skipped when they are read in
- Use this file to temporarily skip over receivers that are
out of service.
- file containing last line in x111auto.dat that was
- x111auto.proc uses this to decide where to start each run.
- x111auto.proc writes each scan as it is performed to this
Making the images: (top)
Images of the x111data are made every so
often. The images consist of:
- Dynamic spectra (spectral density vs freq and time) are made
- data it taken in 60 second blocks (1 sec recs). There is
then a delay before the program cycles around to the next time
this freq block is measured.
- 4*25 MHz records are input for a specified data range (this
may be one or 2 months).
- For each 60 second block of data
- the median spectrum is computed
- a robust harmonic fit is made (1st order linear, 20th
order harmonic) and then used to flatten the 60 seconds of
- A fit rather than a median is used so we don't get rid of
- After flattening all of the data, the 4x25 MHz data is
interpolated to a constant frequency spacing (getting rid of
the freq overlap)
- The image has 1 subtracted and then clipped to +/- .1 Tsys
- Some issues with the images:
- horizontal bright lines may be continuum sources drifting
through the beam.
- For some receivers is didn't start on a block of 4x25
(because the first few bands may have been cut off by the
- In this case, the 4 bands on one row may have not been
taken all at the same time.
x111 dynamic spectra images: (top)
frequencies (MHz) for the 6 images covering the band
- (*0) the bandpass starts to cut off the signal around 1120 and
- (1) the rightmost band 1745-1767 is on the edge of the
- 1175 gps L5
- 1228: gps L2
- 1232,1247,142,1257 : punta salinas radar in modeA
- 1245 - glonass L2
- 1268 - Chinese compass gns
- 1270 - remy radar
- 1330,1350 FAA airport radar
- 1381.05 gps L3
- 1530-1550 inmarsat
- 1575 gps L1
- 1600 - glonass L1
- 1620 - iridium