UK Geodesy Workshop was held at Herstmonceux Castle on 18 & 19 June. Great to meet UK geodesy colleagues there. Otsubo gave a talk on the future laser ranging network. Report & Photo: http://sgf.rgo.ac.uk/news.html

Hello from UK.  One month has passed.  Today’s seminar (Photo: CP) was on various error sources in satellite laser ranging.  Herstmonceux data are very good (pity that it is temporally down) but still have a room for some improvement.

Herstmonceux よりこんにちは．今日は珍しく見事な晴天でしたが，第3回の rainy day seminar で話題提供してきました．今日のネタ，誤差の話，については特に建設的な議論ができたかなと思います．  写真撮影 CP．

Hello from Sussex, UK.  On a rainy/cloudy day like today, we sometimes have a seminar like this at Herstmonceux.  This photo (thanks to BR) shows Otsubo talked about future laser ranging network.

イギリスよりこんにちは．今日のような天気の悪い日は，みなさん観測ができないので，このようなセミナーを開かせてもらっています（撮影： BR）．将来の SLR ネットワークについての研究を紹介しているところ．

A laser retroreflector array is 3D-printed and assembled! This is a 65% scale model of SALAL’s LRA (ILRS Website).  It consists of a body, 9 retroreflectors and 9 hoods.  Created by Nakanishi-san.
大学院生の中西さんが，たいへん苦労してきめ細かく再現してくれました．おつかれさま！ 研究室のソファーのあたりに展示しています．

JPGU 2016 の5月23日午前 測地学一般・GGOS セッション にて，本研究室から次の2件の口頭発表を行いました．

• 「経験的加速度の時間変化で探る衛星の摂動」 服部 晃久, 大坪 俊通
• 「衛星レーザ測距観測網の拡充： 新たな局はどこに？」 大坪 俊通, 松尾 功二, 山本 圭香, 青山 雄一, ホビガー トーマス, 関戸 衛, 久保岡 俊宏

4年の服部くんは初の学会講演会発表でした．

写真は，初日のポスター会場の様子．熱心な高校生（＋高校教員らしきみなさん）がたくさん．

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