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91
Station Performance / Station Performance 2016-2017 (Riga Workshop Spoiler)
« Last post by Toshimichi Otsubo on September 16, 2017, 03:42:40 PM »
Dear Worldwide Laser Ranging Colleagues,

Hello from Tokyo.

In preparation for 2017 ILRS Technical Workshop in Riga http://www.ilrstw2017.lu.lv, I have just generated and uploaded a number of charts on station performance from various aspects.


Period: July 2016 to June 2017.
Satellites: LAGEOS-1, LAGEOS-2, AJISAI, STARLETTE, STELLA and LARES.
POD Software: c5++.  Station positions are solved for.  Atm + hyd loading displacements are applied.  Grav coeffs 5x5 are solved for with some empirical acceleration params.

I will be able to only present only a small part of them in my presentation (Session 2),
but I am willing to discuss these results with everyone. 

See you soon in Latvia,
Toshi
---
Toshimichi Otsubo (t.otsubo@r.hit-u.ac.jp)
Hitotsubashi University

92
Data and Software Questions / Re: What are the Software Languages used for SLR?
« Last post by kalvis on September 14, 2017, 07:25:04 PM »
Legacy software is C and  x86 assembly  for telescope control, Labview and Delphi for data processing. Moving to C#/F#/Python/C for all tasks

Kalvis Salmins

93
In-Sky Safety / Re: On telescope camera for plane spotting
« Last post by kalvis on September 14, 2017, 07:01:31 PM »
In our experience FOV is  sufficient  to have  a time to manually use safety switch to block outgoing laser beam. From the other hand - plane entering FOV of camera is a quite rare event for our system and location.
94
Open a Discussion / Re: Tracking CZ-2C rocket bodies with NORMAL laser
« Last post by ZhipengLiang on September 04, 2017, 08:34:09 AM »
Hi,
Dear Zhipeng,

Borowiec tracks regulary (since January 1, 2017) two CZ2C targets, 28480 and 31114. They give us very interesting results.

Kind regards,
Pawel

I am very happy to hear that. And I have good news that Changchun's historical data about these two targets are now disclosed. You can access them with the following FTP server:


IP address: [210.72.87.239]
user: laserspinrb              password: Pa55w0rd_2017                     access: read only


For now both targets' normal point data till April 2017 are online. For fullrate data, I still have problem in preserving multiple reflection patterns. Any help is welcome.

The access is now read-only. May make it read-write access or even move to sddis, if people are interested.
95
Open a Discussion / Re: Meteo sensor
« Last post by Pawel Lejba on June 21, 2017, 11:26:13 AM »
Thanks !
96
Open a Discussion / Re: Meteo sensor
« Last post by pywang on June 19, 2017, 01:43:27 PM »
In Graz, we have:

1) MET3A from Paroscientific, delivering all 3 meteorological parameters for standard ranging, since long time;

2) PTU301 from Vaisala, bought in 2015, for SP-Dart (hopefully you know what is SP-Dart  :D)

We made a 4-days pressure data comparison between MET3A and PTU301, 1 sample /minute, we got::

----Average of differences= 0.062 mBar (MET3A< PTU301 )
----RMS of differences       = 0.044 mBar

In addition, we have another barometer also from Paroscientific (Model 740-16B) in our laser room.
The difference between MET3A and 740-16B is checked always when starting a pass, and a difference of > 0.3 mbar will be reported as a warning, just to avoid any hardware/software/artificial accidents.

-----------------------------------------------------------------------------------------------------------------------------

In 2015, we also made a market investigation:

1) Paroscientific provides MET4(~8.3k Euros) and MET4A (with fan-aspired, (~9,0k Euros)
2) Vaisala PTU301, about 2.6k Euros excl. tax
3) Climatronics(USA), ALLinONE (even include wind info.), about 2.5k dollors. Needs to be checked / tested.

-----------------------------------------------------------------------------------------------------------------------------

By the way, please remember that SLR expects the pressure value at the system invariant point (crossing of Az /EL axis in the telescope).

Graz has measured the pressure difference between this system invariant point and the location of the sensor; this difference (a constant value) is applied to all  measurements of  air pressure.
97
Open a Discussion / Meteo sensor
« Last post by Pawel Lejba on June 16, 2017, 10:57:31 AM »
Dear Colleagues,

Borowiec plan to exchange the meteo station. What would you recommend to us ? We have an experience with Vaisala. What is a price of your professional meteo sensor you are using ? I will be very gratefull for any replies.

Kind regards,
Pawel
98
Open a Discussion / Re: Tracking CZ-2C rocket bodies with NORMAL laser
« Last post by Pawel Lejba on June 16, 2017, 10:50:33 AM »
Hi,
Dear Zhipeng,

Borowiec tracks regulary (since January 1, 2017) two CZ2C targets, 28480 and 31114. They give us very interesting results.

Kind regards,
Pawel
99
Lasers / Start Diodes - What is best?
« Last post by Matt Wilkinson on May 04, 2017, 09:46:01 AM »
Hi all

What start diode setups are stations currently using in their lasers to detect laser fires and trigger a timer start? I'll go and find the details of the Herstmonceux diode and post it here, but i know we use a rather cheap diode in to a threshold discriminator.  Is there anything better out there anyone could recommend? Are people satisfied with their start diodes?

When we moved to kHz SLR and lower energy pulses (from 20mJ to 1mJ), the threshold for a start had to be dropped considerably.  And so alignment is critical.  If it is not optimised we can get large RMS values in our calibrations.

Matt
100
Hi all

From about the beginning of 2017, the team at the SGF noticed some increased instability in our terrestrial range calibration values at the level of 2-3 mm.  It was particularly clear on the first calibration of the day being a low value and so we learnt to take at least two calibrations before starting an observing duty.

2 weeks ago we also saw an increase in the RMS of the calibrations and some periodic behaviour in the calibration range values.  We consequently took the kHz laser offline and began using our older 10Hz laser, which had very stable calibration values and RMS.

After some investigation and discussion with High-Q, the team found that the flow rate of the cooling water was much lower than it should have been.  The water used is a reservoir of distilled water, but after 10 years of use something had built up to block the waterways.

Temperatures in the laser bed were not being kept at a stabilised constant, causing energy fluctuations and range errors from the start diode. The temperature would change when the laser began firing after being off for a period (20+ minutes). It would stabilise after approximately 10 minutes, during which time calibration range differences were seen.

Running the flow backwards and using a descaler (Durgol was recommended) brought the flowrate up to specification levels.  Setting the best operating temperature removed the signals in the range values and now the calibration RMS and repeatability are now within acceptable levels.

Needless to say, we will be checking the flowrate more often from now on.

Matt
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