====== 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 into account for when we should be pulling from the spectrum analyser.
  * **Late start tracks:** The current wrapper when run after the schedules start time will try each of the blocks in order until it finds one with a tracking point in the future - this is OK, but it takes a long time to iterate through all the previously observed blocks (~20s for each 5 min block - ~4 mins per hour of catchup). Not a big deal if you are only starting the track <1hr late, however, longer than this and you start to lose a significant amount of your observing time just catching up. Will need to look into a better solution for this - I have a solution which would work for python but need to look into what is possible in the shell script.
  * **Recording from spectrum analyser:** I have written a very ugly script that currently grabs trace outputs from the spectrum analyser every 5 seconds during valid time periods (currently from 90s past the start of the scan to the end time). Between the 5 minute blocks it averages all grabbed spectra together and writes them to a file with the timestamp of the scan.

**Nov 19, 2020:**:
  * **Late start tracks:** The bash script generated during schedule generation has now been updated to include 'if' statements with time conditions - this should fix any issues with starting tracks late. Current version of the scripts can be found on my github in a repository named 'antenna_thrust_scripts' (https://github.com/tiegemccarthy/antenna_thrust_scripts) (Tiege)

**Dec 2, 2020:**:
  * **Schedules** Two tracks prepared for this day - one for KOSMOS 2461 (R735) and one for GPS IIRM-8 (G050) (Tiege)
  * This day was cancelled due to high winds - had a meeting with Lucia, Jamie and Guifre instead. Tracking postponed until next week. (Tiege)

**Dec 8, 2020:**
  * Another cancellation, this time due to post-LBA maintenance on the cryo system. (Tiege)

**Dec 11, 2020:**
  * **Remote track on GPS IIRM-8:** fixed a few issues with the observing setup. First issue was time stamps in the shell wrapper not working on newsmerd - the date command was for some reason reading them as GMT+7 timezone despite the default output of date being in UTC. This has since been fixed. (Tiege)
  * Also fixed a bug in the recording script that occasionally caused a type error when writing out the data with numpy.savetxt(). (Tiege)
  * Wrote a script for doing manual (not scheduled) recording using the spectrum analyser - will be useful for when we need to calibration scans on quasars. (Tiege)

**Dec 15, 2020:**
  * **Draft observing guide:** I have written a rough guide outlining the steps required in order to undertake the GNSS tracks and recording which currently exists [[https://docs.google.com/document/d/1ZQYY4cJqCG02h52L18jyCAuboBhCwgeG2JhKxVYTsHk/edit?usp=sharing|on my google drive]] (Tiege)

**Jan 21, 2021:**
  * **GPS050 tracks:** Finally have a run not being cancelled by weather. Running a full track of GPS050 today (and hopefully tomorrow pending weather) - trying a 3 degree offset on offsource scans as 1 degree was too little in our last run with valid data. Also trying some new spectrum analyzer settings - keeping RBW at 3 MHz and VBW at 10 MHz, but changing span to 999 MHz and sweep points to 333, this should remove the need to resample the data when reducing the data - should know by tomorrow. Ideally we will get another couple of tracks on this source next week to check experiment to experiment repeatability of the results.
  * **Flux calibration** Assuming wind remains pleasant, will get some data on a couple of bright quasar sources - 1934-638 is a little too weak for our setup. Would also be good to get multiple sources so we can check SEFD estimations. Ended up getting a scan of 3C353.  (Tiege)

**Jan 22, 2021:**
  * **GPS050 tracks:** Have a full track from Yesterday and a few hours from today. Needed to extend offset to 4 degrees as 3 degrees still had evidence of both L1 and L2 signal in beam.

**Jan 25, 2021:**
  * **Script changes:** Have changed the recorder to throw out traces from the spectrum analyzer that do not have the expected length - this simplifies data reduction as these traces would need to be removed prior to analysis normally.
  * ** Data reduction:** Track from Jan 21 has been reduced and didn't seem to have many issues (other than incomplete traces) - off source scans with the 3 degree offset still have signal in them and therefore power levels are underestimated. Jan 22 data seems to have a little bit of signal still in the band unfortunately - not sure if its worth going to 5 degrees. Something seems to have happened in the second half of the track on Jan 22 - looks like L1 and L2 signal disappear completely after a certain time. Perhaps there was a windstow I missed, I will check the logs on newsmerd.


**TO DO**:
  * <del>**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</del>
  * **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
  * <del>**next track**: booked in next Wednesday (Nov 18) for more tests</del>
  * **next catchup**: booked in Wednesday (Dec 4)