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Topics - Toshimichi Otsubo

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Dear SLR Station colleagues,

After a few years' break, a number of "station x satellite" systematic residual charts are created using one year data from July 2021 to June 2022.  See you at my poster in Guadalajara or online (

What's new in 2022: ITRF2020 velocity and PSD.  Rodriguez's CoM corrections.  GOCO6S gravity model.  LAGEOS-1 and -2 handled separately.

I am still making the poster and the link will be posted here later.  It is impossible to include all these charts in the poster, so please have a look in advance.

See you in Spain,
Toshimichi Otsubo (
Hitotsubashi University

Data and Software Questions / Software: CPF to Range+Az+El?
« on: February 01, 2020, 05:54:35 AM »
Are there any publicly available software that can produce the [Range, Az, El] time series from CPF for a given station position?  Toshi

Open a Discussion / MPE
« on: October 11, 2017, 12:55:37 PM »
Dear laser ranging colleagues,

On Thursday's session in Riga, we heard a few talks and comments on eye safety issues.  I knew almost nothing about MPE (Maximum permissible exposure) and want to learn a bit.

I was wondering how difficult/realistic it will be to make the energy density low enough (as intended in SLR2000).  But I have a question: in what time window(s) should we worry about our eyes?

I found it hard to understand IEC 60825 even in the Japanese translation, but some of the charts in this wikipedia page is partly understandable (but not sure if trustable).

Let me try to understand by assuming two lasers:
(H) Herstmonceux's:  532 nm, 0.5 mJ, 2 kHz, 10 ps FWHM, beam diameter 3 cm
(S) Stuttgart's:  1064 nm, 0.3 mJ, 10 kHz, 3 ns FWHM, beam diameter 7 cm

(1) Energy per pulse
I guess this chart
  caption: "MPE as energy density versus wavelength for various exposure times (pulse durations)"
is the one to look at.  We can read the MPEs at:
  MPE for (H) = 1e-8 J/cm^2 (where real (H) = 7e-5 J/cm^2)
  MPE for (S) = 2e-6 J/cm^2 (where real (S) = 8e-6 J/cm^2)
so Herstmonceux's pulse is far from eye safety but Stuttgart's is close to eye safety considering the fibre loss.

(2) Energy per longer time span (but how long?)
John Degnan commented that the IR could be dangerous because we cannot see it and the eyes can be exposed for a longer time. 
I am not sure but is this chart
  caption: "Maximum permissible exposure (MPE) at the cornea for a collimated laser beam according to IEC 60825, as energy density versus exposure time for various wavelengths"

useful for this?  Then, we can read at 1 sec (correct?):
  MPE for (H) = 2e-3 J/cm^2 (where real (H) = 0.14e J/cm^2)
  MPE for (S) = 1e-2 J/cm^2 (where real (S) = 8e-2 J/cm^2)
again a similar story as above.

Is my understanding correct?  Can Stuttgart SLR be declared as an eye-safe system by reducing the energy a bit and/or by making the beam aperture large?

Or, if you know the best MPE expert in this community, I would like to contact him/her.


Station Performance / Station Performance 2016-2017 (Riga Workshop Spoiler)
« 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, I have just generated and uploaded a number of charts on station performance from various aspects.

Period: July 2016 to June 2017.
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,
Toshimichi Otsubo (
Hitotsubashi University

Station Performance / Station performance charts (Potsdam Workshop Spoiler)
« on: September 20, 2016, 05:03:20 PM »
Hello from Tokyo.

Just 2 weeks before the Potsdam workshop, we have generated a huge number of station-by-station charts so as to assess+assist the productivity and the quality of every SLR station. 

The details are introduced in the 'systematics' session and the 'clinic' session, but you will be able to directly get to the points if you look at them in advance.

This year, in addition to the usual tests, we look into the calibration (= system delay measurement) - frequency, stability, etc.

// Data span: 1 year = July 2015 to June 2016
// POD: software c5++ R874

Hit-rate (observation success rate) over all fly-over observation chances (El > 20 deg)
(Pages 3 and 5 are just rescaled-without-Yarragadee version of Pages 2
and 4 resp)

LAGEOS-1+2 NP Post-POD RMS vs Session-by-session system delay RMS
(Page 1 >> ZOOM >> Page 2 >> ZOOM >> Page 3)

System delay time series
(1 year span)
(5 day span; one of densely observed periods)

System delay measurement frequency
= Interval between calibration record with different time tags
(blue parts: not a unique measurement? Identical records with different time tags found.)
(X-axis extended for 1824, 1873, 1884 and 7820)

Range bias vs System delay

Range bias vs Intensity (# of returns per NP)

Range bias vs Single-shot RMS

Range bias vs Sun Elevation (day vs night)

See you soon in Potsdam,
The charts are created by:
Toshimichi Otsubo <> and Akihisa Hattori
Hitotsubashi University

Station Performance / SLR Hit Rate 2015
« on: May 11, 2016, 04:38:42 AM »
Hello from Tokyo.

The following link contains the quantity (not the quality) statistics for the productive 20 SLR stations last year.  Please have a look.

  Pass-based hit rate and Normal-point(NP)-based hit rate.
  Average number of normal points per pass.
  Average pass duration, defined as the time between the 1st and the last NP.

Yarragadee's hit rates are really awesome.  Note that the hit rate of the microwave techniques will be almost 100%.

I would also like to point out that some stations do not (try to?) track a satellite for a long time as seen in Figure 3.  I think low orbiters should be observed from horizon to horizon unless there is a conflict with other low orbiters.

Toshimichi Otsubo <>
Hitotsubashi University

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