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Topics - Matt Wilkinson

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Data and Software Questions / CRDv2 experience (as a provider)
« on: October 07, 2019, 01:18:10 PM »
How are you getting on with generating version 2 CRD SLR data files?

At Herstmonceux, we are about to start submitting our data in CRDv2 format. I wrote a Python script to generate the files following a similar method to how we write the CRDv1 files in FORTRAN.

It wasn't too much trouble and i think it is all correct now. If you have not looked at doing this yet, there are changes to be aware of in some of the fields and there are also additional fields:
  • H5 Prediction Header
  • C5 Software Configuration
  • C6 Meteorological Instrumentation Configuration
  • C7 Calibration Target Configuration *new*
  • 41 Calibration Detail Record
  • 42 Calibration "Shot" Record *new*

One major change is the recording of the calibration records.  In the v2 version only one '40' record should be included with additional calibrations recorded as '41'.  The epoch of the '40' record should be the at the middle of the pass segment and the calibration value determined from pre and post measurements.

See the latest CRDv2 document from the ILRS website:

It was clear to me in doing this that more data can be included in the CRD files than we are providing at Herstmonceux.  In time, i will look at including the '30' records for Pointing angles.

We also don't collect the information requested in the '21' Meteorological Supplement Record. Is anyone collecting this information?:
  • Wind speed (m/s)
  • Wind direction (degrees azimuth, North is zero)
  • Weather conditions (two-digit SYNOP/WMO “present weather” code, or “rain”, “snow”, “fog”, “mist”, “clear”, “na”, etc.)
  • Visibility (km)
  • Sky clarity (i.e., zenith extinction coefficient)
  • Atmospheric seeing (arcsec)
  • Cloud cover (%)
  • Sky temperature in degrees Kelvin
We do however collect visibility values and so i will look in to including this in the future. Is there an instrument that anyone is using that reliably provides the rest of this information?

Please share your experience in providing CRDv2 below. Any questions or advice welcome


Mission Tracking Feedback / Recovered: Radioastron
« on: June 14, 2019, 02:18:14 PM »

Lavochkin Association did not manage to establish communication with the Spectr-R satellite. Attempts continued from 10 January to 30 May 2019. The State Commission examined the satellite’s technical condition on 30 May 2019 and decided to finish the RadioAstron observing program. The satellite successfully operated for 7.5 years instead of the originally planned 3 years. The link with the satellite was lost due to the very long exposure to the space radiation which has affected the onboard low-gain antenna communication system. Currently, the Astro Space Center is completing the data transfer, correlation and archiving of the vast amount of unique scientific data. International science teams continue to process, analyze and publish the results.

Open a Discussion / Recovered: 'Space debris EU-ESA agreement'
« on: June 14, 2019, 02:17:24 PM »
Good morning.
How is it going to affect our community this new in relation with space debris applications?

We are designing our new station in order to be compatible with space debris activities in the future if it is necessary.

Dear Laser Tracking Colleagues,

G'Day from Tokyo.

In the 21st International Workshop on Laser Ranging (conference site:, proceedings site:, I presented station-by-station performance charts (printed on 1-metre-long sheets) during the Clinic Session 3 co-hosted with Jose Rodriguez.  Here are the short summary of the analysis and the links to the charts.

Period: July 2017 to June 2018.
29 Stations with > 200 LAGEOS passes in the 1 year span.
More details about the analysis: See

Unlike the previous years' ones, this year's charts are organised PER STATION.  Matrix charts are also provided (printed on the reservse side) to help investigate the cause.

The first part contains:
  Residual wrt Range rate (negative in ascending (first) half, and positive in descending (second) half of a pass)
  Residual wrt Local time (defined by the station longitude, slightly different from the local standard time)
  Residual wrt Range rate (as specified in normal point data)
  Residual wrt Single-shot RMS (as specified in normal point data)
  Residual wrt Skew (as specified in normal point data)
  Residual wrt Kurtosis (as specified in normal point data)
  Residual wrt System delay (1), (2),.. (per system delay 'group')
  System delay (all sat) (including calibration data for other satellites not included in this analysis)
  System delay (A), (B), ... (vertical scale magnified as above)
  Calibration interval (cumulative) (typical calbration interval is at median (50%))

The matrix chart (second  part) labels, top-to-botumn = left-toright,  mean:
  Mon 17: Months from January 2017 (13 for January 2018)
  Hour: Local time
  # ret: Number of returns per NP bin
  Return rate
  RMS: Single-shot RMS
  Kurt: Kurtosis
  Range rate
  System delay (1), (2), ...
  O-C: POD residuals
7090 (Yarragadee),
7941 (Matera),
7825 (Mt Strolmo),
7237 (Changchun),
7105 (Greenbelt),
7810 (Zimmerwald),
7840 (Herstmonceux),
7110 (Monument Peak),
7501 (Hartebeesthoek),
7841 (Potsdam),
7821 (Shanghai),
8834 (Wettzell),
7839 (Graz),
7119 (Haleakala),
7819 (Kunming),
1887 (Baikonur),
7838 (Shimosato),
7249 (Beijing),
7827 (Wettzell),
7407 (Brasilia),
1873 (Simeiz),
1879 (Altay),
7845 (Grasse),
1893 (Katzively),
1891 (Irkutsk),
1868 (Komsomolsk-na-Amure),
1889 (Zelenchukskya),
1886 (Arkhyz),
7811 (Borowiec),

Best Regards,


Today, while writing my own CRD-parsing python3 code, I felt a little bit wheel-reinventing

Since the new CRD/CPF format is going to release at the Canberra meeting, I guess it's time to think about our new CRD2.0 python library?
It should have following functions: verify the CRD2.0 format, extract data, etc.

I found in GitHub the CRD/CPF library from Olli Wilkman:

Could be a good start.

Lasers / Polarisation
« 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.
  • 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]
In the future, we plan to look further at circular polarisation and would be grateful for any advice from those that are able to send circular polarised light.  We also hope to return to looking at controlling the emitted linear polarisation orientation using a 1/2 wave plate.


ILRS Stations / SLR Spring
« on: April 27, 2018, 10:11:55 AM »
Spring at the Herstmonceux SLR station

Mission Tracking Feedback / S-NET tracking
« on: April 06, 2018, 03:15:05 PM »
The 4 S-NET ( satellites were launched on February 01, 2018.  They have been difficult targets up to now. At Herstmonceux, we've had a number of unsuccessful attempts. And i think they have not been tracked by any station in the ILRS network.

However, next week (11th April) we expect to begin to see passes that are partially sunlit and so we will hopefully stand a better chance of getting some returns. This must also be true for other stations.

We will focus on S-NET4 as suggested in the recent ilrs-sta mail (

Please use this space below to comment on your S-NET attempts, successes and failures over the coming weeks. Good luck!

Welcome to the ILRS NESC Forum / Posting a mathematical formula
« on: January 04, 2018, 04:21:59 PM »

To help contributors who want to include formulae in their posts I've installed a program called 'mimetex' which takes LaTeX formatted text and produces a gif image.  It works like this:

[ img]/cgi-bin/mimetex.cgi?f(x)=\int_{-\infty}^xe^{-t^2}dt [/ img]

which without the tag spaces gives:

Please test it out using the post preview.  See here


Open a Discussion / MOVED: Satellite BLITS-M
« on: January 04, 2018, 04:11:02 PM »

In-Sky Safety / FLARM
« on: January 03, 2018, 09:37:05 AM »

I'd like to know more about FLARM and what it can offer SLR stations.

I see the Graz station is using it. Is anyone else?

Despite having a cautionary/avoidance zone for aircraft around the Herstmonceux SLR station, we do get some light aircraft, gliders etc flying over, especially on nice sunny days. This means the observer has to keep a look out.

If this system can raise a proximity alarm then i guess the observer would find it very useful.

Please post your experience. Cheers

Hi all

I hope all those who attended had an enjoyable and productive Workshop in Riga.

I'm sorry i wasn't there. And I know I wasn't the only one who couldn't make it.

So, what did i miss?
  • What did you take away from the Workshop?
  • What were the things you learnt?
  • What was of most interest to you?

Please share your thoughts below


Photography / Night Photography
« on: September 21, 2017, 03:20:03 PM »
Herstmonceux and Orion

Lasers / Start Diodes - What is best?
« 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.


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.


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