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development:gnss_calibration

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GNSS calibration project

Nov 5, 2020: we have set a date for initial test observations, friday Nov 13; some thoughts beforehand:

  • We believe that we can do the measurements from the control room
  • We will select a few suitable satellites (Lucia and Tiege) and use the TLE-RADEC satellite function for the 26m to actually track the satellite (Tiege looks into that – but we have used it previously)
  • All we need for a start is a snapshot from the spectrum analyser over the transmission bands (L1 & L2)
  • What we also need is a calibration of the antenna
  • Once we have a few measurements, we can look into the formulas and try to derive the actual values that we need.

Nov 13, 2020: first tracking tests:

  • setup: split off the multi-feed channel 1, nominally one of the linearly polarized ones; permanently installed; spectrum analyser connected of that; receiver multifeed 2 (L-band), agilent (1st LO) set to 4.1 GHz, 16 dBm output.
  • spechb: on the network via vnc and socket connection; settings: input attenuation manually fixed at 10dBs; center freq and span adjustable; freq 500MHz, span 1 GHz; 100 counts average seems to look good by eye. video bandwidth of 10 MHz, resolution BW 3 MHz, sweep time 2.5 ms. (setup in automatic mode); narrower bandwidth allow better discrimination between RFI and signal; use different tracers; sky range 1.1 - 2.1 GHz;
  • RFI: bruny island microwave link ~330MHz IF (1430 sky), mobile phones above 1.8 GHz, something at about 60-70 MHz (1160-70, blocking L5?)
  • tracks: tracking using the satellite tracking module (sattrack); scheduled with 10sec updates.
  • sattrack: satplt.pl window is the one to look at for current track; infos in spaceX_26m.pdf; has to be run on newsmerd; to stop: abort in vdesk window 3 - emergency: big red button

Nov 18, 2020: Tiege solo show:

  • Spectrum analyser traces When I got out here the spectrum analyser was not showing the expected spectrum despite L-band being on axis. Removing cable produced no change in the output, looks like after it was unplugged it needed to have the 'pre-set' button pushed (I think) in order for it to switch to the 'RF in' input. In the process of troubleshooting this I seem to have changed the behaviour of trace 1 and am not sure how to change it back to how it was. Trace 2 is still set to a 100 count average.
  • Tracking testing Testing the shell wrapper calling the 5 minute block schedules. All seems to run fine so far - Looks like it takes between 60s and 120s for the telescope to settle between schedule blocks - will need to take this in account for when we should be pulling from the spectrum analyser.

TO DO:

  • prepare tracks for 5 min on source off source (for 1 satellite at a time); probably try 1 sec updates; how does sattrack handle this? code up 5 minute tracks to load after each other (run in sequence) - after the track finished, the antenna sits at the final az/el
  • define spectral analyser output - pulling & scripting seems to work - but what and how long to write out data?; question what resolution and freq span? Why is TRACE output always 500 points? https://cdn.rohde-schwarz.com/pws/dl_downloads/dl_common_library/dl_manuals/gb_1/f/sfl_1/FSL_OperatingManual_en_12.pdf
  • SEFD calibration - need to work out how to do this? VirgoA or Hydra is strong - use on/offs and spec an. Nominal SEFD about 400-500 Jy
  • define an output from the spectral analyser - a dataset that we can work on; do some tests regarding resolution etc
  • try repeatability - observe the identical satellite for 3 days in a row and compare values
  • get value table ready - try to replicate the tracking table Peter Steigenberger sent through; figure out boresight angle etc (Lucia to ask Ron/Peter)
  • have a look at subsequent estimation - get all the necessary values together, code an estimator? first understand the code
  • next track: booked in next Wednesday (Nov 18) for more tests
  • next catchup: booked in Wednesday (Dec 4)
/home/www/auscope/opswiki/data/attic/development/gnss_calibration.1605669623.txt.gz · Last modified: 2020/11/18 03:20 by Tiege McCarthy