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Messages - delpino@riga

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Station Equipment Questions / Re: Meteorological station
« on: July 19, 2018, 12:46:10 PM »
Serna Yebes

I think that all participants on the Networks and Engineering Standing Committee Forum will agree on the following points:

•   The coordinates and in particular the height difference between the barometric sensor in use and the telescope invariant point should be included, measured and known in the local geodetic network.

•   The sensors (and in particular the barometer, which is the most difficult to calibrate “in situ”) should be calibrated periodically, (how we define “periodic” will be another looooong discussion).

•   What is now the sampling data rate of the current Yebes meteorological station?
Most SLR and GPS stations works at 10 minutes (at sharp second) sampling rate.
Remember that the pressure resolution asked is 0.1 milibar, and most of time, the pressure change rate in 10 minutes is less or equal than that.

•   The meteodata should be time tagged and available immediately at the local network, not only the last measurement done, but also the proceeding ones.

•   This is because the best practice is to include both pre- and post- meteorological values on the Normal point and this Normal Point file should be generated and delivered as soon as possible.
But if you do the “batch filtering” every few hours, you need to have access to the data of at least the last couple of days (to have a monthly file is a good compromise)

•   If the “local microclimate” at Yebes is (more or less) the same at the meteorological and SLR places, for example both places are surrounded by grass, this distance is not a problem.
In Riga we are using a common meteorological station at a distance of 32m (GPS) and 50m (SLR)

•   Do the current meteorological station has an anemometer?
Do you have strong winds at Yebes?
Because for really strong winds, automatically closing the roof/cupola/clamshell will be a good security measure against flying objects.
At the new buildings at GFZ Potsdam, all the windows have external Venetian blinds connected to a central anemometer. When the wind reaches a limit all the blinds are automatically lowered to protect the windowpanes

•   Invest the money on the best clarity/rain sensor in which the rain/snow alarm can be used to automatically close the SLR roof AND on a high quality all-Sky camera!
When several satellites are visible and it is partially cloudy, the all-Sky camera is the best tool for the on-the-spot tracking optimization.

And if you have a LOT of money project, and buy the independent, well calibrated SLR basic meteorological station situated at the SLR invariant height, no one at the SLR community will complain!.

We are installing in Riga a network of SLR temperature sensors using RapsberryPI's and the software in Python.
One RapsberryPI with 2 sensors is monitoring the laser room (where the 25 meters calibration path single mode optical fiber is stored) and another sensor is on the PMT thermal box attached to the Telescope receiving Coudé path (on open air when tracking) but connected to the Laser Room sharing the heating/cooling.

The second RapsberryPI with 2 sensors is monitoring the Control/Electronics room and the CFD/Event Timer electronics

Here is a plot of the daily max/min temperatures at the PMT box

Station Equipment Questions / Meteorological station
« on: May 30, 2018, 01:03:12 PM »
There is a point that was mentioned already by Kalvis Salmins in Annapolis:

the current log file do not have a dedicated line on the section 12 to report the difference height between the meteo sensors (in particular the barometric sensor) and the invariant point.
Anybody knows if and where this information is available for all the stations?

The pressure is reported on the CRD's in mbar in format 7.2, but according to the note on section 3.4.2. of the CRD format description, only the pressure changes by 0.1mB are significant enough to report.
what should be the recommended tolerance for measuring the height difference and/or maximum allowed height error if we want to set the sensor exactly at the invariant point level?

Another comment answering to pywang:
There is a work in progress from many years about having a traveling absolute barometer used to calibrate in-situ the SLR local barometers in Europe.

In this moment we have the GFZ Potsdam absolute barometer in Riga, and in July-August one intern from the bilateral Estonia-Latvia SpaceTEM Eslat project ( will use it to calibrate our secondary Vaisala PTU300 sensor.
After that we will send it back to Potsdam during the autumn.

So if another station wants to do the same, contact Sven Bauer at GFZ about loaning the absolute barometer, and us for some practical hints on doing and processing the data.

ILRS Stations / Riga Station 1884 photos
« on: September 26, 2017, 12:04:51 PM »
3 photos from Riga station 1884

Ideas / Re: Making satellites visible during daylight ranging
« on: July 11, 2016, 11:46:08 AM »
In the early 90's while tracking in Cuba, I also saw ERS-1 several times in daylight, using the 60 cm main mirror guiding ocular with a dicroic mirror blocking the 532 band.
Will be interesting to try using a CCD with enhanced IR sensitivity and/or a combination of filters to improve the contrast.
Let's share any experience on this topic!

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