51
Mission Tracking Feedback / Re: S-NET tracking
« Last post by Matt Wilkinson on June 04, 2018, 09:34:14 AM »See the attached for a plot of kHz residuals from S-NET1 taken over the weekend at Herstmonceux SLR station
Recent Posts
52
Mission Tracking Feedback / LARGE campaign 2018
« Last post by jose_sgf on May 30, 2018, 02:11:49 PM »Here are the results of the 2018 LARGE campaign in terms of passes and NPs collected by the network. It appears that stations of the Russian network did not participate in the campaign (they only tracked GLONASS satellites), so they have not been included in the statistics.
We believe that the inferior tracking coverage of the Galileo constellation is to a great extent explained by the lower cross section of the retroreflector arrays relative to those mounted on the Glonass satellites. Our experience tracking these objects tells us that the LRAs mounted on the first Galileo spacecraft (Galileo 101-104) are obviously superior to the ones that suceeded them (Galileo 2XX). Among both the primary and secondary groups of Galileo targets there is one spacecraft carrying the first LRA versions (Galileo-102 and Galileo-103). Both of them have received significantly higher tracking coverage than the rest of spacecraft in their respective groups (~60% more NP data for Galileo-102, ~40% more NP data for Galileo-103). Meanwhile, the data yield for Galileo-103 and Galileo-104 is lower than for Glonass satellites by approximately 20% in terms of NP data. It must be noted that the LRAs onboard the Glonass satellites selected for the LARGE campaign have a higher cross section than the previously employed ones, and superior to those used in any of the Galileo constellation.
Except for Compass-M3, coverage for the Compass constellation has been low as a) the geosynchronous satellites are only partially visible from Europe (if at all); b) prediction quality for Compass-MS1 and MS2 is not adequate for intensive SLR tracking.
We believe that the inferior tracking coverage of the Galileo constellation is to a great extent explained by the lower cross section of the retroreflector arrays relative to those mounted on the Glonass satellites. Our experience tracking these objects tells us that the LRAs mounted on the first Galileo spacecraft (Galileo 101-104) are obviously superior to the ones that suceeded them (Galileo 2XX). Among both the primary and secondary groups of Galileo targets there is one spacecraft carrying the first LRA versions (Galileo-102 and Galileo-103). Both of them have received significantly higher tracking coverage than the rest of spacecraft in their respective groups (~60% more NP data for Galileo-102, ~40% more NP data for Galileo-103). Meanwhile, the data yield for Galileo-103 and Galileo-104 is lower than for Glonass satellites by approximately 20% in terms of NP data. It must be noted that the LRAs onboard the Glonass satellites selected for the LARGE campaign have a higher cross section than the previously employed ones, and superior to those used in any of the Galileo constellation.
Except for Compass-M3, coverage for the Compass constellation has been low as a) the geosynchronous satellites are only partially visible from Europe (if at all); b) prediction quality for Compass-MS1 and MS2 is not adequate for intensive SLR tracking.
53
Solutions, Advice and Experience / Keeping our laser and electronics temperature
« Last post by delpino@riga on May 30, 2018, 01:40:18 PM »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
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
54
Station Equipment Questions / Meteorological station
« Last post by delpino@riga 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 (https://estlat.eu/en/estlat-results/spacetem.html) 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.
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 (https://estlat.eu/en/estlat-results/spacetem.html) 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.
55
Station Equipment Questions / Re: Meteorological station
« Last post by pywang on May 25, 2018, 06:46:42 AM »In Graz, we are using MET3A from Paroscientific.
And another pressure sensor--740-16B . Because pressure is the most critical met parameter, the 2 pressure sensor data are compared after each reading; a warning mesage is issued if the difference is > 0.3 hPa. Both are setup at different altitudes (not on the same as the reference point), and values are corrected to our invariant point.
All met devices are read by a dedicated PC in 1 Minute intervals. Any program in need for met data is accessing this data.
Unfortunately, since I am here(almost 4 years) never heard about somebody made any calibration.
And another pressure sensor--740-16B . Because pressure is the most critical met parameter, the 2 pressure sensor data are compared after each reading; a warning mesage is issued if the difference is > 0.3 hPa. Both are setup at different altitudes (not on the same as the reference point), and values are corrected to our invariant point.
All met devices are read by a dedicated PC in 1 Minute intervals. Any program in need for met data is accessing this data.
Unfortunately, since I am here(almost 4 years) never heard about somebody made any calibration.
56
Station Equipment Questions / Meteorological station
« Last post by Clement_GRSM on May 24, 2018, 02:14:40 PM »Dear all,
we are thinking on the measurement of the meteorological parameters regarding systematic bias and accuracy of SLR station.
We would like to know:
1) on the choice of the equipment
what kind of equipment do you use ?
What parameters do you monitor ?
What metrological performances have your system ?
2) on the installation place and the corrections
Where do you place the sensors ?
Do you apply corrections (for example, on the pressure if the barometer is not at the same elevation as the cross-axis of the telescope)?
3) on calibrations
How often do you calibrate your equipment ?
Thanks
Clément
we are thinking on the measurement of the meteorological parameters regarding systematic bias and accuracy of SLR station.
We would like to know:
1) on the choice of the equipment
what kind of equipment do you use ?
What parameters do you monitor ?
What metrological performances have your system ?
2) on the installation place and the corrections
Where do you place the sensors ?
Do you apply corrections (for example, on the pressure if the barometer is not at the same elevation as the cross-axis of the telescope)?
3) on calibrations
How often do you calibrate your equipment ?
Thanks
Clément
57
Lasers / Polarisation
« Last post by Matt Wilkinson on April 27, 2018, 10:28:09 AM »We need to talk about polarisation!
At Herstmonceux, we are still emitting linear polarised laser light after an attempt to make it circular with a 1/4 wave plate failed. The circular polarisation was lost through the coudé mirrors before the beam left the emitter.
Would everyone please describe here the polarisation characteristics of their SLR systems.
Thanks
Matt
At Herstmonceux, we are still emitting linear polarised laser light after an attempt to make it circular with a 1/4 wave plate failed. The circular polarisation was lost through the coudé mirrors before the beam left the emitter.
Would everyone please describe here the polarisation characteristics of their SLR systems.
- What is polarisation state of the laser light emitted by your SLR system?
- How are you achieving this?
- Have you tested this and know that you are sending what you think you are at all telescope azimuths and elevations?
- Can you control the emitted polarisation?
- What are the polarising properties of your receive path [At Hx, we found our receive path to be highly selective to polarisation and we had to replace our dichroic mirror]
Thanks
Matt
58
ILRS Stations / SLR Spring
« Last post by Matt Wilkinson on April 27, 2018, 10:11:55 AM »Spring at the Herstmonceux SLR station
59
Mission Tracking Feedback / Re: S-NET tracking
« Last post by Yarragadee on April 24, 2018, 08:42:54 AM »Dear All,
Snet4 pass doy 114/0430
cpf: DLR6131
timebias -30mS
Returns: 89
Snet4 pass doy 114/0430
cpf: DLR6131
timebias -30mS
Returns: 89
60
Mission Tracking Feedback / Re: S-NET tracking
« Last post by Yarragadee on April 15, 2018, 07:39:54 AM »Dear All,
The details on the two passes we have got returns on so far:
Doy 103/1600
Sic: 6207
CPF: DLR6031
Timebias +40mS
X-track: ~0 mdeg
Returns: 96
Comments: Returns steady in range window @ 40mS. Return strength similar to
technosat and faded out during pca period.
DOY 104/1605
Sic: 6207
CPF: DLR6031
Timebias -30mS
X-track: ~0 mdeg
Returns: 167/64 ( two segments)
Comments: Returns steady.
Now I will see if I can attach the excel spreadsheet of the O-C's - Randall
The details on the two passes we have got returns on so far:
Doy 103/1600
Sic: 6207
CPF: DLR6031
Timebias +40mS
X-track: ~0 mdeg
Returns: 96
Comments: Returns steady in range window @ 40mS. Return strength similar to
technosat and faded out during pca period.
DOY 104/1605
Sic: 6207
CPF: DLR6031
Timebias -30mS
X-track: ~0 mdeg
Returns: 167/64 ( two segments)
Comments: Returns steady.
Now I will see if I can attach the excel spreadsheet of the O-C's - Randall