「Research」カテゴリーアーカイブ

講演完了報告: JPGU 2016 幕張

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.

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SLR Hit Rate 2015

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.

hitrate15a
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.

hitrate15b
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.

hitrate15c
Fig. 3 (click to enlarge). Average pass duration, defined as the time between the 1st and the last NP

FY2016 = Sabbatical year

入学・進学おめでとうございます.平成28年度=2016年度,大坪は着任10年目にして研修年をいただくことになりまして,学部ゼミナール(4年のみ)と大学院ゼミナールを除いて,一橋大学で担当する講義はありません.一方で,国立天文台の客員教授に就きました(国立天文台客員教授等).研究推進のため海外(欧州)研修も計画中です.

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 MKP4010157_R

JASON-3 and a number of GALILEO and GLONASS satellites added to our QC analysis

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.