Published online today!
“Effective expansion of satellite laser ranging network to improve global geodetic parameters”
Toshimichi Otsubo, Koji Matsuo, Yuichi Aoyama, Keiko Yamamoto, Thomas Hobiger, Toshihiro Kubo-oka and Mamoru Sekido
Earth Planets and Space (Frontier Letter)
→ Earth Planets and Space Website, Open Access
An 2015 update of SLR performance assessment. The methodology was reported at the 17th International Workshop on Laser Ranging (Slide PDF) in 2011.
We have worked up some interesting statistics about the ratio of successful ranging observations with respect to all possible observations (> 20 degrees of elevation). Let us call it “hit rate” here – this is somehow similar to a batting average of a baseball (not a cricket) player. In other words, it is equal to the probability that a satellite flying over a station is laser-ranged from the station. Sky conditions are not taken into account.
The most productive 20 stations (ILRS Global Performance 2015 4Q) in 2015 are tested here. We show the results for four satellite groups: (1) “ETALON-1 and -2”, (2) “LAGEOS-1 and -2”, (3) “LARES”, (4) “STARLETTE and STELLA”. Fig. 1 shows the pass-based hit rate and the NP-based hit rate.
Fig 1 (click to enlarge). Pass-based hit rate and Normal-point(NP)-based hit rate.
As we see the ratio between the pass-based hit rate (black) and the NP-based hit rate (grey) differs by stations, the average number of NPs per pass is now plotted in Fig. 2. Note that this is the average among observed passes.
Fig. 2 (click to enlarge). Average number of normal points per pass.
It is recommended to track a wide coverage from horizon to horizon, even if it is sometimes interrupted. The average duration of a pass is therefore plotted in Fig. 3.
Fig. 3 (click to enlarge). Average pass duration, defined as the time between the 1st and the last NP
Otsubo takes a sabbatical year during Apr 2016 – Mar 2017, which means only a few seminar courses are offered at Hitotsubashi University. He is appointed as a guest professor of the National Astronomical Observatory, and plans to stay in Europe this year.
Photo: 2016-04-01 MK
We have added the following satellites to our SLR QC analysis.
JASON-3 (ILRS, AVISO) (abbreviated as JAS3).
GALILEO-201, 202, 203, 204, 205, 206, 208 and 209 (ILRS) (F201 to F209).
GLONASS-125, 128, 133 and 134 (ILRS) (GL25, GL28, GL33, GL34).
We also changed the bias estimation procedure. A pass of high-altitude satellites (GNSS and ETALON) should have >= 4 good NPs, 2 hour coverage, and both ascending and descending parts.